DRC-2022-018843 - 0901a068810b89f6

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Energy Fuels Resources (USA) Inc'
225 Union Blvd. Suite 600
Lakewood, CO,US' 80228
3Mn42140
gusl*gnetgyfucl$"com
Jnly 13,2022
Sent VIA EXPEDITED DELMRY
Mr. Doug Hansen
Director
Division of Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
Salt Lake City, UT 84116
Re: Transmittal of Hydrogeology Report for the White Mesa Uranium Mill, Blanding Utah Pursuant to
Part [V.D of the Utah Groundwater Discharge Permit.
Dear Mr. Hansen:
Enclosed are two copies of the Energy Fuels Resources (USA) Inc. ("EFRI") White Mesa Uranium Mill
Hydrogeology Report for the facility and surrounding area, pursuant to Part IV.D of the Utah Groundwater
Discharge Permit ("GWDP").
The revised Hydrogeology Report incorporates the relevant information from studies conducted at the White
Mesa Mill since the submission of the previous Hydrogeology Report.
If you should have any questions regarding this report, please contact me at 303-389-4t34.
Yours very truly,
t*tlq-;-t''{
ENnncv Furr,s RBsouncrs (USA) INC.
Kathy Weinel
Director, Regulatory Compliance
CC: Scott Bakken
David Frydenlund
Logan Shumway
Garrin Palmer
Teny Slade
Stewart Smith (HGC)
i liiinlhiri iiJltiUriiT#'r
DRC-2022-018843

HYDRO GEO CHEM, INC.
Environmental Science & Technology

HYDROGEOLOGY OF THE
WHITE MESA URANIUM MILL
BLANDING, UTAH

July 13, 2022

Prepared for:

ENERGY FUELS RESOURCES (USA) INC.
225 Union Boulevard, Suite 600
Lakewood, Colorado 80228

[phone]

Prepared by:

HYDRO GEO CHEM, INC.
51 W. Wetmore, Suite 101
Tucson, Arizona 85705-1678
[phone]

Project Number 7180000.00-02.0

Hydrogeology of the White Mesa Uranium Mill Blanding, Utah
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TABLE OF CONTENTS

1. INTRODUCTION .............................................................................................................. 1
2. BACKGROUND AND OVERVIEW ................................................................................ 3
2.1 Overview of Site Hydrogeology ............................................................................. 5
2.1.1 Geology/Stratigraphy .................................................................................. 5
2.1.2 Hydrogeologic Setting ................................................................................ 6
2.1.3 Perched Water Zone .................................................................................... 7
2.1.4 Seeps and Springs in Relation to Perched Zone Hydrogeology ............... 11
2.1.5 Tailings Management System ................................................................... 13
3. DETAILED SITE HYDROGEOLOGY ........................................................................... 15
3.1 Stratigraphy and Formation Characteristics .......................................................... 15
3.1.1 Brushy Basin Member .............................................................................. 15
3.1.2 Burro Canyon Formation/Dakota Sandstone ............................................ 15
3.1.2.1 Dakota Sandstone....................................................................... 16
3.1.2.2 Burro Canyon Formation ........................................................... 17
3.1.3 Mancos Shale ............................................................................................ 19
3.1.4 Pyrite Occurrence in the Dakota Sandstone and Burro
Canyon Formation .................................................................................... 21
3.2 Contact Descriptions ............................................................................................. 22
3.2.1 Brushy Basin Member/Burro Canyon Formation Contact Elevations ..... 22
3.2.2 Mancos Shale/Dakota Contact Elevations ................................................ 23
3.2.3 Soils Above the Dakota and /or Mancos................................................... 24
3.3 Perched Water Elevations, Saturated Thicknesses, and Depths to Water ............ 25
3.4 Interpretation of Cross-Sections ........................................................................... 26
3.4.1 Central and Northeast Areas ..................................................................... 26
3.4.2 Southwest Area ......................................................................................... 27
3.5 Perched Water Occurrence and Flow ................................................................... 28
3.5.1 Overview ................................................................................................... 28
3.5.1.1 General Site Flow Pattern .......................................................... 29
3.5.1.2 Influence of Pumping and Wildlife Pond Seepage on
Flow and Dissolved Constituent Concentrations ...................... 30
3.5.2 Nitrate Investigation Area ......................................................................... 34
3.5.3 Vicinity of Chloroform Plume .................................................................. 36
3.5.4 Beneath and Downgradient of the Tailings Management System ............ 43
3.5.4.1 Overview .................................................................................... 43
3.5.4.2 Water Balance Near DR-2 and DR-5......................................... 44
3.5.4.3 Water Balance Near Ruin Spring and Westwater Seep ............. 46
3.6 Perched Water Migration Rates and Travel Times ............................................... 48
3.6.1 Nitrate Investigation Area ......................................................................... 48
3.6.2 Vicinity of Chloroform Plume .................................................................. 49
3.6.3 Beneath and Downgradient of Tailings Management System .................. 50
3.6.3.1 Vadose Zone .............................................................................. 51
3.6.3.2 Perched Water Zone Downgradient of Tailings
Management System ................................................................. 52

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TABLE OF CONTENTS (Continued)

3.7 Implications for Seeps and Springs....................................................................... 54
3.7.1 Westwater Seep and Ruin Spring ............................................................. 54
3.7.2 Cottonwood Seep ...................................................................................... 55
3.7.3 Potential Dilution of Perched Water Resulting from Local
Recharge of the Dakota and Burro Canyon Near Seeps and Springs ....... 56
3.8 Implications for Transport of Chloroform and Nitrate ......................................... 57
4. COMPOSITION OF DAKOTA SANDSTONE AND BURRO
CANYON FORMATION ................................................................................................. 59
4.1 Mineralogy ............................................................................................................ 59
4.2 Pyrite Occurrence.................................................................................................. 59
4.3 Expected Influence of Transient Conditions, Oxygen Introduction, and the
Mancos and Brushy Basin Shales on Dakota/Burro Canyon Chemistry .............. 61
4.4 Implications for Perched Water Chemistry and Natural Attenuation of
Nitrate and Chloroform ......................................................................................... 65
4.4.1 Pyrite Degradation by Oxygen .................................................................. 65
4.4.2 Nitrate Degradation by Pyrite ................................................................... 66
4.4.2.1 Other Relevant Studies Regarding Nitrate Reduction
by Pyrite .................................................................................... 69
4.4.2.2 Comparison to Oostrum Site ...................................................... 70
4.4.3 Chloroform Reduction .............................................................................. 71
5. SUMMARY OF PERCHED GROUNDWATER MONITORING AND STUDIES ...... 73
5.1 Chloroform Plume ................................................................................................ 74
5.2 Nitrate Plume ........................................................................................................ 75
5.3 MW-24A Study ..................................................................................................... 77
5.4 Proposed Phase 2 Study ........................................................................................ 79
6. SUMMARY AND CONCLUSIONS REGARDING MILL HYDROGEOLOGY ......... 81
6.1 Perched Water Pore Velocities in the Nitrate Plume Area ................................... 89
6.2 Perched Water Pore Velocities in the Vicinity of the Chloroform Plume ............ 89
6.3 Hydrogeology and Perched Water Pore Velocities in the Southwest Area .......... 90
6.4 Fate of Chloroform and Nitrate............................................................................. 91
7. PROPOSED CELLS 5A AND 5B .................................................................................... 93
8. REFERENCES ................................................................................................................. 95
9. LIMITATIONS STATEMENT ...................................................................................... 105

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TABLE OF CONTENTS (Continued)

TABLES

1 Results of Slug test Analyses Using KGS and Bouwer-Rice Solutions
2 Results of Recovery and Slug Test Analyses Using Moench Solution
3 Estimated Perched Zone Hydraulic Properties Based on Analysis of Observation Wells
Near MW-4 and TW4-19 During Long Term Pumping of MW-4 and TW4-19
4 Summary of Hydraulic Properties White Mesa Uranium Mill from TITAN (1994)
5 Properties of the Dakota/Burro Canyon Formation White Mesa Uranium Mill from
TITAN (1994)
6 Hydraulic Conductivity Estimates for Spring Flow Calculations
7 Hydraulic Conductivity Estimates for Travel Time Calculations Paths 1, 2A, and 2B
8 Hydraulic Conductivity Estimates for Travel Time Calculations Paths 3-6
9 Estimated Perched Zone Pore Velocities Along Path Lines
10 Results of XRD and Sulfur Analysis in Weight Percent
11 Tabulation of Presence of Pyrite, Iron Oxide, and Carbonaceous Fragments in Drill Logs
12 Sulfide Analysis by Optical Microscopy
13 Summary of Pyrite in Drill Cuttings and Core
14 Summary of Nitrate Degradation Rates
15 Pyrite Contents in samples From White Mesa Mill and Oostrum, Netherlands Site

FIGURES

1A White Mesa Site Plan Showing Location of Perched Wells, Piezometers, Lithologic
Cross-Sections (as of Q4, 2021) And Proposed New Cells 5A and 5B.
1B White Mesa Site Plan Showing Location of Perched Wells, Piezometers, and Nitrate and
Chloroform Plume Boundaries
2 Lithologic Column
3 White Mesa Stratigraphic Section Based on Lithology of WW-3 from TITAN (1994)
4 Photograph of the Contact Between the Burro Canyon formation and the Brushy Basin
Member
5 Kriged 4th Quarter, 2021 Water Levels, White Mesa Site
6 Annotated Photograph Showing East Side of Cottonwood Canyon (looking east toward
White Mesa from west side of Cottonwood Canyon)
7 Extent of the Western Interior Sea (Cretaceous)
8 Kriged Top of Brushy Basin, White Mesa Site
9A Kriged Top of Bedrock, White Mesa Site
9B Kriged Top of Bedrock Using Revised Depth to Mancos Data, White Mesa Site
10 Kriged Top of Dakota Sandstone, White Mesa Site
11A Kriged Top of Bedrock Showing Approximate Mancos Thickness, White Mesa Site
11B Kriged Top of Bedrock Showing Approximate Revised Mancos Thickness, White Mesa
Site

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TABLE OF CONTENTS (Continued)

FIGURES (Continued)

12 Approximate Geoprobe Boring and Cross-Section Locations, White Mesa Site
13 Soil Cross Sections East of Ammonium Sulfate Crystal Tanks, White Mesa Site
14 4th Quarter, 2021 Perched Zone Saturated Thicknesses and Brushy Basin Paleoridges and
Paleovalleys, White Mesa Site
15 4th Quarter, 2021 Depths to Perched Water, White Mesa Site
16A Interpretive Northeast-Southeast Cross Section (NE-SW), White Mesa Site
16B Interpretive Northeast-Southwest Cross Section (NE2-SW2), White Mesa Site
17 Interpretive Northwest-Southeast Cross Section (NW-SE), White Mesa Site
18A Interpretive East-West Cross Sections (W-E and W2-E2) Southwest Investigation Area
18B Interpretive East-West Cross Section (WNW-ESE) Southwest Investigation Area
19 Interpretive North-South Cross Sections (S-N) Southwest Investigation Area
20 DR Series Piezometer Depths to Water 2Q 2011 to 4Q 2021
21 Kriged 4thQuarter, 2021 Water Levels Showing Inferred Perched Water Pathlines and
Kriged Nitrate and Chloroform Plumes
22 Kriged 4th Quarter, 2021 Water Levels and Estimated Capture Zones, White Mesa Site
(detail map)
23 Kriged 4th Quarter, 2011 Water Levels, White Mesa Site
24 TW4-4 and TW4-6 Water Levels
25 Kriged 4th Quarter, 2021 Water Levels Showing Inferred Perched Water Pathlines
Downgradient of the Tailings Management System, White Mesa Site
26 Kriged 4th Quarter, 2021 Water Levels Showing Inferred Perched Water Flow Pathlines
Near Ruin Spring and Westwater Seep
27 Kriged 4th Quarter, 2021 Water Levels Showing Inferred Perched Water Flow used for
Travel Time Estimates and Kriged Nitrate and Chloroform Plumes
28 Photograph of the Westwater Seep Sampling Location July 2010
29 Photograph of the Contact Between the Burro Canyon Formation and the Brushy Basin
Member at Westwater Seep
30 Kriged 4th Quarter, 2021 Water Levels showing Kriged Nitrate and Chloroform Plumes
and Inferred Perched Water Pathlines, White Mesa Site
31 Water Level in Wells Near TW4-27
32 White Mesa Site Plan Showing Pyrite Occurrence in Perched Borings
33 Proposed New Cell 5A and 5B Monitoring Wells and Piezometer, White Mesa Site

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TABLE OF CONTENTS (Continued)

APPENDICES

A Lithologic Logs
B Well Construction Schematics
C INTERA Soil Boring Logs
D Historic Water Level Maps (Seep and Spring Elevations Not Considered in Contouring)
E Topographic and Geologic Maps
F Hydrogeology Beneath Proposed Cells 5A and 5B and Proposed New Monitoring
Installations

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Hydrogeology of the White Mesa Uranium Mill Blanding, Utah
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1. INTRODUCTION
This report provides an update to the July 11, 2018 report Hydrogeology of the White Mesa
Uranium Mill, Blanding Utah, and Recommended Locations of New Perched Wells to Monitor
Proposed Cells 5A and 5B (the 2018 Hydrogeologic Report; HGC [2018d]).
The present report incorporates all the elements of the 2018 Hydrogeologic Report with
appropriate updates. Section 7 includes updates provided in HGC (2018e) and HGC (2019a)
regarding additional monitoring installations for proposed new cells 5A and 5B. The proposed
new installations are subject to change as approval of the final design is pending.
The present report considers the additional hydrogeologic data collected at the site from the first
quarter of 2018 through the fourth quarter of 2021. Calculations provided in the 2018
Hydrogeologic Report are updated based on the more recent data. Some of the additional data
and updated calculations include:
1. Quarterly perched water level and analytical (chloroform and nitrate concentration) data;
2. Lithologic data collected from wells MW-24A, MW-38 through MW-40, TW4-40
through TW4-43, and TWN-20 and TWN-21;
3. Hydraulic test data collected from wells MW-24A, MW-38 through MW-40, TW4-40
through TW4-43, and TWN-20 and TWN-21;
4. Rates of perched groundwater movement and conservative solute travel times, in
particular within the southwest portion of the site (downgradient of the tailings
management system [TMS]);
5. Perched water balance calculations in the southwest portion of the site;
6. Pyrite occurrence;
7. Changes in chloroform and nitrate plumes; and
8. Chloroform and nitrate degradation rates.

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2. BACKGROUND AND OVERVIEW
Figure 1A is a site map showing general site features and the locations of perched groundwater
wells and piezometers (as of the fourth quarter of 2021), springs, and lithologic cross-sections.
Figure 1B shows fourth quarter, 2021 kriged perched groundwater elevation contours and the
kriged fourth quarter 2021 boundaries of the chloroform and nitrate plumes at the site.
Since the time period covered by the previous (2018) Hydrogeologic Report, monitoring wells
MW-38, MW-39, and MW-40 were installed in the southeastern portion of the site (between
MW-17 and MW-22) during the first quarter of 2018 (HGC, 2018c). These wells are located far
cross-gradient of the tailings management system (TMS). Also during the first quarter of 2018,
two new chloroform wells (TW4-40 and TW4-41) were installed as discussed in HGC (2018b).
Chloroform well TW4-40 was installed approximately 200 feet south of TW4-26 and chloroform
pumping well TW4-41 was installed immediately north-northeast of TW4-4 to augment pumping
in the vicinity of TW4-4. In addition, chloroform monitoring well TW4-42 was installed
approximately 200 feet south of TW4-40 during April, 2019 (HGC, 2019b); nitrate monitoring
wells TWN-20 and TWN-21 were installed west of TWN-7 during April, 2021 (HGC, 2021a);
and chloroform monitoring well TW4-43 was installed approximately 200 feet east-southeast of
TW4-30 during September, 2021 (HGC, 2021b).
Hydrogeologic investigation of the site has been ongoing since the initial investigation in 1977-
1978 (Dames and Moore, 1978). Major hydrogeologic and groundwater investigations include
Dames and Moore (1978); UMETCO (1993); UMETCO (1994); TITAN (1994); International
Uranium (USA) Corporation (IUSA) and Hydro Geo Chem, Inc. (HGC) [2000]; IUSA and HGC
(2001); HGC (2004); HGC (2007b); INTERA (2007a); INTERA (2007b); INTERA (2008);
Hurst and Solomon (2008); INTERA (2009); HGC (2010g); INTERA (2012a); INTERA
(2012b); HGC (2012b); HGC (2012c); HGC (2014a); HGC (2014b); and HGC (2018d).
Investigations to date and more than 41 years of perched groundwater monitoring indicate that
operation of the TMS (cells 1 through 4B in Figures 1A and 1B) has not impacted perched
groundwater. The lack of impact is detailed in Hurst and Solomon (2008) and various INTERA
documents (INTERA, 2007a; INTERA 2007b; INTERA, 2008; INTERA, 2010; INTERA,
2012a; INTERA 2012b; INTERA, 2013a; INTERA, 2013b; INTERA, 2014a; INTERA, 2014b;
INTERA, 2014c; INTERA, 2015; INTERA, 2016; INTERA, 2017; INTERA, 2018;
INTERA,2019a; INTERA, 2019b; INTERA, 2019c; and INTERA, 2020). Additional documents
demonstrating the lack of impact include EFRI, 2020; EFRI, 2021a; EFRI 2021c; EFRI, 2022a;
and EFRI, 2022d.

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Perched groundwater was impacted by operation of a temporary laboratory facility that was
located at the site prior to and during the construction of the Mill, and from septic drain fields
that were used for laboratory and sanitary wastes prior to operation of the Mill’s TMS circa 1980
(HGC, 2007b; HGC, 2022). Laboratory wastes prior to 1980 were first disposed to the
abandoned scale house leach field, and later to the former office leach field. Disposal of
laboratory wastes to the abandoned scale house and former office leach fields is considered the
source of the chloroform plume (defined by concentrations greater than 70 micrograms per liter
[µg/L]) located upgradient to cross-gradient (northeast to east) of the TMS (Figure 1B). The
eastern portion of the chloroform plume likely originated from the abandoned scale house leach
field (located immediately north-northwest of TW4-18 [Figure 1B]), and the western portion
from the former office leach field (located in the immediate vicinity of TW4-19 [Figure 1B]).
Perched groundwater has also been impacted by nitrate (INTERA, 2009). The nitrate plume
(Figure 1B), defined by concentrations greater than 10 milligrams per liter (mg/L), contains
elevated chloride (exceeding 100 mg/L) and extends from upgradient (northeast) of the TMS to a
portion of the area beneath the TMS as described in the Nitrate Corrective Action Plan (nitrate
CAP)[HGC, 2012a]. The precise source(s) of the nitrate plume are not well defined. However,
the footprint of a former agricultural/stock watering pond referred to as the ‘historical pond’ is
located beneath the upgradient portion of the nitrate plume and extends to the north of the plume
(Figure 1B). This pond was active from the early part of the 20th century until the area was re-
graded as part of Mill construction circa 1980 (HGC, 2012a). This pond is considered one of the
likely historical sources of nitrate and chloride to the nitrate plume. Ammonium sulfate handling
in the vicinity of the ammonium sulfate crystal tanks (southeast of TWN-2 [Figures 1A and 1B])
is considered the only potential Mill contribution of nitrate to the nitrate plume and has been
addressed through implementation of Phase 1 of the nitrate CAP [HGC (2012a) and EFRI
(2013)].
The chloroform and nitrate plumes have been under remediation by pumping since 2003 and
2013, respectively. Actions taken by the Mill are consistent with the preliminary chloroform
CAP (HGC, 2012a) and final GCAP (Utah Department of Environmental Quality Division of
Solid Waste and Radiation Control [DWMRC], 2015; and with the nitrate CAP (HGC, 2012a).
Because the northwestern portion of the chloroform plume commingles with the central portion
of the nitrate plume, the effects of the pumping systems overlap, and the initiation of nitrate
pumping in 2013 caused redistribution of chloroform as discussed in HGC (2022). Both plumes
are discussed in more detail in Sections 3, 4, and 5.
Appendix A contains copies of lithologic logs from site perched monitoring wells and
piezometers. Appendix B contains copies of perched well construction schematics. Appendix C

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contains logs of borings installed by INTERA as part of the nitrate investigation that supported
the nitrate CAP. Logs of soil borings installed per Phase I of the nitrate CAP are provided in
EFRI (2013).
2.1 Overview of Site Hydrogeology
TITAN (1994) provides a detailed description of site hydrogeology based on information
available at that time. A brief summary of site hydrogeology that is based in part on TITAN
(1994) and updated with information from the literature and more recent site investigations is
provided below.
2.1.1 Geology/Stratigraphy
The White Mesa Uranium Mill is located within the Blanding Basin (the Basin) of the Colorado
Plateau physiographic province. Bedrock units exposed in the Basin include Upper Jurassic
through Cretaceous sedimentary rocks (Figure 2, from Doelling, 2004). The general succession,
in ascending order, is the Upper Jurassic Morrison Formation, the Lower Cretaceous Burro
Canyon Formation, and the Upper Cretaceous Dakota Sandstone and Mancos Shale. Most
exposures of the Morrison Formation consist of the Brushy Basin Member. Typical of large
portions of the Colorado Plateau province, the rocks within the Basin are relatively undeformed.
The Mill has an average elevation of approximately 5,600 feet above mean sea level (ft amsl)
and is underlain by unconsolidated alluvium and indurated sedimentary rocks. Indurated rocks
include those exposed within the Basin (described above), and consist primarily of sandstone and
shale. The indurated rocks are relatively flat lying with dips generally less than 3º. The alluvial
materials consist primarily of aeolian silts and fine-grained aeolian sands with a thickness
varying from a few feet to as much as 25 to 30 feet across the site. The alluvium is underlain by
the Dakota Sandstone and Burro Canyon Formation, and where present, the Mancos Shale. The
Dakota and Burro Canyon are sandstones having a total thickness ranging from approximately
55 to 140 feet, and, because of their similarity, are typically not distinguished in lithologic logs at
the site. Beneath the Burro Canyon Formation lies the Morrison Formation, consisting, in
descending order, of the Brushy Basin Member, the Westwater Canyon Member, the Recapture
Member, and the Salt Wash Member. The Brushy Basin and Recapture Members of the
Morrison Formation, classified as shales, are very fine-grained, have a very low permeability,
and are considered aquicludes. The Brushy Basin Member is primarily composed of bentonitic
mudstones, siltstones, and claystones. The Westwater Canyon and Salt Wash Members also have
a low average vertical permeability due to the presence of interbedded shales.

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Beneath the Morrison Formation lie the Summerville Formation, an argillaceous sandstone with
interbedded shales, and the Entrada Sandstone. Beneath the Entrada lies the Navajo Sandstone.
The Navajo and Entrada Sandstones constitute the primary aquifer in the vicinity of the site. The
Entrada and Navajo Sandstones are separated from the Burro Canyon Formation by
approximately 1,000 to 1,100 feet of materials having a low average vertical permeability.
Groundwater within this system is under artesian pressure in the vicinity of the site, is of
generally good quality, and is used as a secondary source of water at the site. Stratigraphic
relationships beneath the site are summarized in Figure 3 (adapted from TITAN, 1994 and based
on the lithology of water supply well WW-3, located just northwest of TWN-2 [Figure 1A]).
The Upper Jurassic Morrison Formation is the youngest Jurassic unit in the Basin. In many
places an unconformity separates the Morrison Formation from underlying Middle Jurassic
strata. The Morrison was deposited in a variety of depositional environments, ranging from
aeolian to fluvial and lacustrine. Much of the Morrison is composed of fluvial sandstone and
mudstone that have sources to the west and southwest of the Basin (Peterson and Turner-
Peterson, 1987). The upper Brushy Basin Member (a bentonitic shale), was deposited in a
combination of lacustrine and marginal lacustrine environments (Turner and Fishman, 1991).
The contact between the Morrison Formation and overlying strata has been subject to discussion.
In the southeastern part of the Basin, the Lower Cretaceous Burro Canyon Formation overlies the
Morrison Formation. The contact between the Burro Canyon Formation and the Morrison
Formation has been interpreted as a disconformity (Young, 1960); however, Tschudy et al.,
(1984) indicated that the Burro Canyon Formation may be a continuation of deposition of the
Morrison Formation. More recent studies by Aubrey (1992) also suggest interfingering between
the Morrison Formation and overlying units.
Kirby (2008) indicates that the contact between the Morrison Formation and the Burro Canyon
Formation (between the Brushy Basin Member of the Morrison and the Burro Canyon
Formation) near Blanding, Utah is disconformable with “local erosional relief of several feet”.
Data collected from perched borings at the site that penetrate the Brushy Basin Member are
consistent with a disconformable, erosional contact in agreement with Kirby (2008).
2.1.2 Hydrogeologic Setting
The site and vicinity has a dry to arid continental climate, with an average annual precipitation of
approximately 13.3 inches, and an average annual lake evaporation rate of approximately 47.6
inches. Recharge to major aquifers (such as the Entrada/Navajo) occurs primarily along the

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mountain fronts (for example, the Henry, Abajo, and La Sal Mountains), and along the flanks of
folds such as Comb Ridge Monocline.
Although the water quality and productivity of the Navajo/Entrada aquifer are generally good,
the depth (approximately 1,200 feet below land surface [ft bls]) makes access difficult. The
Navajo/Entrada aquifer is capable of yielding significant quantities of water to wells (hundreds
of gallons per minute [gpm]). Water in WW-series supply wells completed across these units at
the site rises approximately 800 feet above the base of the overlying Summerville Formation
(TITAN, 1994).
2.1.3 Perched Water Zone
Perched groundwater occurs within the Dakota Sandstone and Burro Canyon Formation beneath
the site and is used on a limited basis to the north (upgradient) of the site because it is more
easily accessible than the Navajo/Entrada aquifer. Perched groundwater originates mainly from
precipitation and local recharge sources such as unlined reservoirs (Kirby, 2008) and is
supported within the Burro Canyon Formation by the underlying aquiclude (Brushy Basin
Member of the Morrison Formation).
Water quality of the Dakota Sandstone and Burro Canyon Formation is generally poor due to
high total dissolved solids (TDS) in the range of approximately 1,100 to 7,900 milligrams per
liter (mg/L), and is used primarily for stock watering and irrigation. The saturated thickness of
the perched water zone generally increases to the north of the site, increasing the yield of the
perched zone to wells installed north of the site. The generally low permeability of the perched
zone limits well yields. Although sustainable yields of as much as 4 gallons per minute (gpm)
have been achieved in site wells penetrating higher transmissivity zones near unlined wildlife
ponds, yields are typically low (<1/2 gpm) due to the generally low permeability of the perched
zone. Even site wells that yielded as much as 4 gpm during the first few months of pumping
eventually saw yields drop to about 1 gpm or less. As of the fourth quarter of 2021, total
sustainable pumping from the 16 wells comprising the chloroform and nitrate pumping systems
was just under 6 gpm.
In addition, many of the perched monitoring wells purge dry and take several hours to more than
a day to recover sufficiently for groundwater samples to be collected. During redevelopment
(HGC, 2011b) many of the perched wells went dry during surging and bailing and required
several sessions on subsequent days to remove the proper volumes of water.

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Although perched groundwater extends into the overlying Dakota Sandstone within areas having
greater saturated thicknesses, perched groundwater at the site is hosted primarily by the Burro
Canyon Formation, which consists of a relatively hard to hard, fine- to medium-grained
sandstone containing siltstone, shale and conglomeratic materials. As discussed above, the Burro
Canyon Formation is separated from the underlying regional Navajo/Entrada aquifer by
approximately 1,000 to 1,100 feet of Morrison Formation and Summerville Formation materials
having a low average vertical permeability. As discussed above, the Brushy Basin Member of the
Morrison Formation (a bentonitic shale), lying immediately beneath the Burro Canyon
Formation, forms the base of the perched water zone at the site. Figure 4 is a photograph of the
contact between the Burro Canyon Formation and the underlying Brushy Basin Member taken
from a location along Highway 95 north of the Mill. This photograph illustrates the transition
from the cliff-forming sandstone of the Burro Canyon Formation to the slope-forming Brushy
Basin Member.
Figure 5 is a perched groundwater elevation contour map generated from fourth quarter, 2021
data. Historic water level maps based on data from 1990, 1994 and 2002 are provided in
Appendix D. Note that maps shown in Appendix D are based only on water levels from perched
zone wells and do not include seep and spring elevations.
As shown in Figure 5 and Appendix D, perched water flow across the site is generally from
northeast to southwest. This general flow pattern has been consistent based on perched water
level data collected beginning with the initial site investigation described in Dames and Moore
(1978). Perched water discharges in seeps and springs located to the west, southwest, east, and
southeast of the site.
Beneath and south of the TMS, in the west central portion of the site, perched water flow is
south-southwest to west-southwest. Flow on the western margin of the mesa south of the TMS is
generally southerly, approximately parallel to the mesa rim (where the Burro Canyon Formation
is terminated by erosion). On the eastern side of the site perched water flow is also generally
southerly to southwesterly.
Perched water flow beneath and downgradient of the Mill site and TMS is influenced by perched
water discharge points Westwater Seep, located west to west-southwest of the TMS, and Ruin
Spring, located southwest of the TMS. The overall southwesterly flow pattern is locally
influenced by former seepage from the unlined wildlife ponds. Because of relict mounding near
the northern wildlife ponds, flow direction ranges from locally westerly (west of the ponds) to
locally easterly (east of the ponds).

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In general, perched groundwater elevations have not changed significantly at most of the site
monitoring wells since installation, except in the vicinity of the three unlined wildlife ponds and
sixteen pumping wells (shown in Figures 1A and 1B). For example, relatively large increases in
water levels occurred between 1994 and 2002 at MW-4 and MW-19, located in the east and
northeast portions of the site, as discussed in HGC (2007b). These water level increases in the
northeastern and eastern portions of the site were the result of seepage from the northern wildlife
ponds. Piezometers PIEZ-1 through PIEZ-5, shown in Figure 5, were installed in 2001 to
investigate these changes. The mounding associated with the wildlife ponds and the general
increase in water levels in the northeastern portion of the site resulted in a local steepening of
groundwater gradients near the ponds.
Since the first quarter of 2012, after water delivery to the two northern wildlife ponds ceased, the
perched groundwater mound associated with these ponds (the northern mound) began to
diminish. In addition, reduced water delivery to the southern wildlife pond caused the associated
perched groundwater mound (the southern mound) to diminish. Since the first quarter of 2012,
water levels have declined within the northern mound by as much as 25 feet (at PIEZ-2), and
within the southern mound by more than 23 feet (at PIEZ-5). The decay of the groundwater
mounds associated with the wildlife ponds has caused reductions in hydraulic gradients over
those portions of the site that experienced prior increases resulting from former water delivery to
the ponds.
Although use of these ponds specifically as wildlife ponds began in the early 1990s, the
northernmost pond contained water as least as early as 1984 (based on aerial photography). The
1985 editions of United States Geological Survey (USGS) topographic maps covering the
western (Black Mesa Butte map) and eastern (Blanding South map) portions of the Mill property
show the Mill buildings but none of the cells within the future TMS. The northern wildlife pond
is shown as water-bearing, but the historical pond, which shows up on pre-1978 aerial
photography, is not shown. The absence of the historical pond is consistent with the elimination
of that pond during regrading as part of Mill construction circa 1979. The features shown on
these maps suggest that they are representative of the time period between approximately 1979
and the year the maps were published, 1985. Therefore, based on the features shown on these
USGS topographic maps, the northern wildlife pond could have been water bearing as early as
about 1979.
In addition a perched groundwater mound extending beneath the future Mill site was likely
present at the time of the initial site investigation. Dames and Moore (1978) indicated that the
depth to water beneath the future Mill site was a relatively shallow 56 ft bls, while depths to
water beneath the future TMS were generally greater than 90 ft bls. Dames and Moore (1978)

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also indicated that the hydraulic gradient beneath the future Mill site was a relatively large 0.03
feet per foot (ft/ft), while the hydraulic gradient beneath the future TMS was a more typical 0.01
ft/ft. The relatively shallow depth to water and relatively steep hydraulic gradient beneath the
future Mill site are consistent with a perched groundwater mound originating from a source
upgradient to the north (historical pond) or northeast (northernmost wildlife pond).
In addition to the impacts of wildlife and historical pond seepage on site water levels, pumping
of chloroform wells MW-4, MW-26, TW4-1, TW4-2, TW4-4, TW4-11, TW4-19, TW4-20 (now
abandoned), TW4-21, TW4-37, TW4-39, TW4-40 and TW4-41; and nitrate wells TW4-22,
TW4-24, TW4-25, and TWN-2; has depressed the perched water table locally and contributed to
reduced average hydraulic gradients to the south and southwest of these wells. Pumping is
designed to remove chloroform and nitrate associated with the chloroform and nitrate plumes
shown on Figure 1B.
Hydraulic testing of perched zone wells yields a hydraulic conductivity range of approximately 2
x 10-8 to 0.01 centimeters per second (cm/s) as discussed in HGC (2012b). Hydraulic
conductivity estimates obtained from perched wells installed and tested subsequent to HGC
(2012b) also fall within this range (HGC, 2013a; HGC, 2013b; HGC, 2014c; HGC, 2015; HGC,
2016; HGC, 2018b; HGC, 2018c; HGC, 2019b; HGC, 2020; HGC, 2021a; and HGC, 2021b).
Hydraulic conductivity estimates are summarized in Tables 1 through 4. Table 1 provides
estimates of hydraulic conductivity from slug test data analyzed using the KGS and Bouwer-Rice
solutions available in AQTESOLV (HydroSOLVE, 2000). Table 2 summarizes recovery and
slug test data analyzed using the Moench solutions in WHIP (HGC, 1988) and AQTESOLV. The
estimates provided in Tables 1 and 2 are based on HGC (2002); HGC (2005); HGC (2010c);
HGC (2010d); HGC (2010e); HGC (2010f); HGC (2011a); HGC (2011c); HGC (2013a); HGC
(2013b); HGC (2014c); HGC (2015); HGC (2016); HGC (2018b); HGC (2018c); HGC (2019b);
HGC (2021a); and HGC (2021b). Table 3 summarizes analyses of test data collected during
long-term pumping within the chloroform plume area using the Theis solutions available in
AQTESOLV (HGC, 2004). Table 4 (from TITAN, 1994) summarizes hydraulic conductivity
estimates based on testing prior to 1994.
In general, the highest perched zone permeabilities and well yields are in the area of the site
immediately northeast and east (upgradient to cross gradient) of the TMS. A relatively
continuous, higher permeability zone associated with the chloroform plume and consisting of
poorly indurated (poorly cemented) coarser-grained materials has been inferred to exist in this
portion of the site (HGC, 2007b; HGC, 2018a). Because their existence requires both coarse
grain size and poor cementation, such relatively continuous, higher permeability zones are
expected to be relatively rare at the site.

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Perched zone permeabilities downgradient (southwest) of the TMS are generally low. The low
permeabilities and relatively shallow hydraulic gradients downgradient of the TMS result in
average perched groundwater pore velocity estimates that are among the lowest on site.
2.1.4 Seeps and Springs in Relation to Perched Zone Hydrogeology
Hydro Geo Chem (2010g) discusses the relationships between the perched water zone and seeps
and springs at the margins of White Mesa. The relationships between seeps and springs and site
geology/stratigraphy are provided in Figure E.1 and Figure E.2 of Appendix E. Key findings of
HGC (2010g) include the following:
1. Incorporating the seep and spring elevations in perched water elevation contour maps
produces little change with regard to perched water flow directions except in the area
west of the TMS and near Entrance Spring. West of the TMS, incorporation of Westwater
Seep creates a more westerly hydraulic gradient. Westwater Seep appears to be
downgradient of the western portion of the TMS (Figure 5); and Ruin Spring is
downgradient of the eastern portion of the TMS (Figure 5). Westwater Seep is the closest
apparent discharge point west of the TMS and Ruin Spring is the closest discharge point
south-southwest of the TMS. Including the Entrance Spring elevation on the east side of
the site creates a more easterly gradient in the perched water contours, and places
Entrance Spring more directly downgradient of the northern wildlife ponds. Seeps and
springs on the east side of the mesa are either cross-gradient of the TMS or are separated
from the TMS by a groundwater divide.
2. Ruin Spring and Westwater Seep are interpreted to occur at the contact between the
Burro Canyon Formation and the Brushy Basin Member. Corral Canyon Seep, Entrance
Spring, and Corral Springs are interpreted to occur at elevations within the Burro Canyon
Formation at their respective locations but above the contact with the Brushy Basin
Member. All seeps and springs (except Cottonwood Seep which is located within the
Morrison Formation near the Brushy Basin Member/Westwater Canyon Member contact)
are associated with conglomeratic portions of the Burro Canyon Formation. Provided
they are poorly indurated (poorly cemented) the more conglomeratic portions of the
Burro Canyon Formation are likely to have higher permeabilities and the ability to
transmit water more readily than finer-grained portions. This behavior is consistent with
on-site drilling and hydraulic test data that associates higher permeability with the poorly
indurated coarser-grained horizons detected east and northeast of the TMS that are
associated with the chloroform plume).
3. Cottonwood Seep is located more than 1,500 feet west of the mesa rim in an area where
the Dakota Sandstone and Burro Canyon Formation (which hosts the perched water
system) are absent due to erosion. Cottonwood Seep occurs near a transition from slope-
forming to bench-forming morphology (indicating a change in lithology). Cottonwood
Seep (and 2nd Seep located immediately to the north [annotated photograph provided in
Figure 6]) are interpreted to originate from coarser-grained materials within the lower
portion of the Brushy Basin Member (or upper portion of the Westwater Canyon

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Member) and are therefore not (directly) connected to the perched water system at the
site.
4. Only Ruin Spring appears to receive a predominant and relatively consistent proportion
of its flow from perched groundwater. Ruin Spring originates from conglomeratic Burro
Canyon Formation sandstone where it contacts the underlying Brushy Basin Member, at
an elevation above the alluvium in the associated drainage. Westwater Seep, which also
originates at the contact between the Burro Canyon Formation and the Brushy Basin
Member, likely receives a significant contribution from perched water. All seeps and
springs other than Ruin Spring (and 2nd Seep just north of Cottonwood Seep) are located
within alluvium occupying the basal portions of small drainages and canyons. The
relative contribution of flow to these features from bedrock and from alluvium is
indeterminate.
5. All seeps and springs are reported to have enhanced flow during wet periods. For seeps
and springs associated with alluvium, this behavior is consistent with an alluvial
contribution to flow. Enhanced flow during wet periods at Ruin Spring, which originates
from bedrock above the level of the alluvium, likely results from direct recharge of Burro
Canyon Formation and Dakota Sandstone outcropping near the mesa margin in the
vicinity of Ruin Spring. This recharge would be expected to temporarily increase the flow
at Ruin Spring (as well as other seeps and springs where associated bedrock is directly
recharged) after precipitation events.
6. The assumption that the seep or spring elevation is representative of the perched water
elevation is likely to be correct only in cases where the feature receives most or all of its
flow from perched water and where the supply is relatively continuous (for example at
Ruin Spring). The perched water elevation at the location of a seep or spring that receives
a significant proportion of water from a source other than perched water may be different
from the elevation of the seep or spring. The elevations of seeps that are dry for at least
part of the year will not be representative of the perched water elevation when dry. Some
uncertainty therefore results from including these seeps and springs in the contouring of
perched water levels. However, even if such springs are sometimes dry, the presence of
cottonwoods suggests that perched groundwater is close to the surface at these locations.

Although there are uncertainties associated with incorporation of seep and spring elevations into
maps depicting perched water elevations or maps depicting the Burro Canyon Formation/Brushy
Basin Member contact elevations, post-2010 perched water elevation maps incorporate seep and
spring elevations other than Cottonwood Seep, and post-2010 contact elevation maps incorporate
Westwater Seep and Ruin Spring elevations.
As discussed above, Cottonwood Seep was interpreted in HGC (2010g) to be associated with
coarser-grained materials within the lower portion of the Brushy Basin Member. The
justification for this interpretation is based primarily on 1) the rate of flow at Cottonwood Seep,
which is typically estimated to range between approximately 1 and 10 gpm (consistent with

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Dames and Moore, 1978), 2) the need for relatively permeable materials to transmit this rate of
flow, and 3) the change in morphology near Cottonwood Seep indicating a change in lithology.
The change in morphology from slope-former to bench-former just east of Cottonwood Seep can
be seen in the topographic map included in Appendix E (Figure E.1) and the annotated
photograph provided in Figure 6.
The upper portion of the Brushy Basin Member, which hydraulically isolates the perched zone
from underlying materials, is composed primarily of bentonitic mudstone, claystone, and shale.
The rate of flow at Cottonwood Seep is inconsistent with the materials found within the upper
portion of the Brushy Basin Member but is consistent with coarser-grained materials expected
either within the lower portion of the Brushy Basin Member or within the upper portion of the
underlying Westwater Canyon (sandstone) Member. The relationship between Cottonwood Seep
and lithology is shown on the geologic map provided in Appendix E (Figure E.2) and Figure 6.
As shown in Figures 6 and E.1, Cottonwood Seep is located approximately 230 feet below the
base of the perched zone defined by the contact between the cliff-forming Burro Canyon
Formation and the underlying slope-forming Brushy Basin Member. The change in morphology
from slope-former to bench-former occurs within the lower portion of the Brushy Basin Member
(or the upper portion of the Westwater Canyon Member), between the termination of the perched
zone at the mesa rim and Cottonwood Seep. The bench-like area hosting Cottonwood Seep
begins at the change in morphology east of Cottonwood Seep and terminates west of
Cottonwood Seep where a cliff-forming sandstone, interpreted to be within the Westwater
Canyon Member, is exposed. The contact between the Westwater Canyon Member and the
Brushy Basin Member is interpreted to be located between this sandstone outcrop and the change
in morphology from slope-former to bench-former. This places Cottonwood Seep at the
transition between the Brushy Basin Member and the underlying Westwater Canyon Member.
This is consistent with the stratigraphy provided in Figure 3 which places the contact between
the Brushy Basin Member and the Westwater Canyon Member at elevations between
approximately 5,220 and 5,230 ft amsl in this portion of the site, within 5 to 15 feet of the
elevation of Cottonwood Seep (5,234 ft amsl).
Details of the coarse-grained nature of the lower portion of the Brushy Basin Member are
consistent with Shawe (2005) as will be discussed in Section 3.1.1.
2.1.5 Tailings Management System
The existing TMS includes cells 1 through 4B (Figure 1A). Details of the construction of cells 2
though 4A are provided in UMETCO (1993). Mill tailings are disposed in lined cells excavated

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below grade into the upper Dakota Sandstone. Cells 2 and 3 are underlain by a synthetic liner
placed over compacted bedding material. The bedding material serves as a drain layer. The drain
layer and a sand drain on the downstream embankment are connected to a leak detection lateral.
Slime drains were installed above the liner in each cell within the area having the lowest
topographic elevation.
Cell 4A and cell 4B have a geoclay liner overlain by geotextile and a double synthetic liner. The
leak detection systems lie between the two synthetic liners.
Although the cells are equipped with leak detection systems, and monitoring activities have not
detected impacts to the perched aquifer from tailings disposal (as discussed in Section 2), the
Mill installed additional perched monitoring wells between existing wells on the downgradient
margin of the TMS and between existing cells to function as an ‘early warning system’ for any
potential impacts to perched water. These additional wells, MW-23 through MW-25, and MW-
27 through MW-31, were installed and tested in 2005 (HGC 2005). At this time, temporary wells
TW4-15 and TW4-17, located at the eastern edge of the cell complex and installed in 2002
(HGC, 2002), were converted to permanent status and renamed MW-26 and MW-32,
respectively. Subsequently, upon installation of cell 4B, MW-33 through MW-37 were added to
the west and south (downgradient) edges of the cell.

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3. DETAILED SITE HYDROGEOLOGY
A detailed description of site hydrogeology is provided in the following Sections.
3.1 Stratigraphy and Formation Characteristics
The site stratigraphy is summarized in Figure 3. Details of formations underlying the site that are
stratigraphically above the Westwater Canyon Member of the Morrison Formation are provided
in the following Sections.
3.1.1 Brushy Basin Member
As discussed in Sections 2.1.1 and 2.1.3, the upper portion of the Brushy Basin Member is
composed of bentonitic mudstone, claystone, and shale, which hydraulically support the perched
groundwater zone and isolate it from underlying materials.
The upper portion of the Brushy Basin Member is described by Shawe (2005) as “principally
mudstone; it contains only minor amounts of sandstone, conglomeratic sandstone, and
conglomerate as discontinuous lenses”. Shawe (2005) describes the lower portion of the Brushy
Basin as coarser-grained, having “mudstone layers which contain, near their base, lenses
lithologically similar to sandstone of the Salt Wash Member, and near their top, conglomeratic
sandstone lenses”.
With regard to the vicinity of Cottonwood Seep (discussed in Section 2.1.4), the expectation of
coarser-grained materials is consistent with its location near the transition from the lower
coarser-grained portion of the Brushy Basin Member into the underlying Westwater Canyon
Member. As discussed in Craig et al. (1955), and Flesch (1974), the Westwater Canyon Member
intertongues with the Brushy Basin Member. Craig et al. (1955) state “The Westwater Canyon
Member forms the lower portion of the upper part of the Morrison in northeastern Arizona,
northwestern New Mexico, and places in southeastern Utah and southwestern Colorado near the
Four Corners, and it intertongues and intergrades northward into the Brushy Basin Member”.
3.1.2 Burro Canyon Formation/Dakota Sandstone
Although the Dakota Sandstone and Burro Canyon Formations are often described as a single
unit due to their similarity, previous investigators at the site have distinguished between them.
The Dakota Sandstone is a relatively hard to hard, generally fine-to-medium grained sandstone
cemented by kaolinite clays. The Dakota Sandstone locally contains discontinuous interbeds of
siltstone, shale, and conglomeratic materials. Porosity is primarily intergranular. The underlying

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Burro Canyon Formation is the primary host of the perched groundwater at the site. The Burro
Canyon Formation is similar to the Dakota Sandstone but is generally more poorly sorted,
contains more conglomeratic materials, and becomes argillaceous near its contact with the
underlying Brushy Basin Member (TITAN, 1994). The permeabilities of the Dakota Sandstone
and Burro Canyon Formations at the site are generally low. Porosities and water contents
measured in samples of Dakota Sandstone and Burro Canyon Formation collected from borings
MW-16 and MW-17 are described in Sections 3.1.2.1 and 3.1.2.2 below. Porosity estimates from
these borings agree with measurements reported by MWH (MWH, 2010) for archived samples
collected from borings MW-23 and MW-30.
No significant joints or fractures within the Dakota Sandstone or Burro Canyon Formation have
been documented in any wells or borings installed across the site (Knight-Piésold, 1998). Any
fractures observed in cores collected from site borings are typically cemented, showing no open
space. The Knight-Piésold findings are consistent with the evaluation of a 1994 drilling program
provided in HGC (2001a) and with examination of drill core samples collected during
installation of MW-3A, MW-23, MW-24, MW-28, MW-30, and TW4-22 in 2005 (HGC, 2005).
3.1.2.1 Dakota Sandstone
The Dakota Sandstone, named by Meek and Hayden (1862) for exposures in northeastern
Nebraska, rests disconformably upon the Burro Canyon Formation where present. A three-fold
lithologic sequence occurs in many localities, and consists of a basal conglomeratic sandstone
with an underlying disconformity, a middle unit of carbonaceous shale and coal, and an upper
unit of evenly-bedded sandstone which intertongues with the overlying Mancos Shale. These
strata have been described as deposits of transitional environments which accompanied the
westward transgressing Mancos Sea (Young, 1973).
The basal conglomerate represents floodplain braided channel deposits which extend into the
adjacent paludal environment. The carbonaceous shales are partly marshy but most formed in
lagoon ponds, tidal flats and tidal channels of the lagoonal environment just seaward of the
marsh belt. The evenly-bedded sandstone was formed at the shoreline as a mainland or barrier
beach deposit of the littoral marine environment. Faunal evidence summarized by O'Sullivan et
al., (1972) indicates that the lower part of the Dakota Sandstone is of Early Cretaceous age and
the upper part is of Late Cretaceous age.
Based on samples collected during installation of wells MW-16 (abandoned) and MW-17,
located beneath and immediately downgradient of the TMS at the site (Figures 1A and 1B),
porosities of the Dakota Sandstone range from 13.4% to 26%, and average 20% (Table 5) which

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is nearly the same as the average porosity of 19% reported by MWH (MWH, 2010) for archived
sandstone samples collected from MW-23 and MW-30.
Water saturations from MW-16 and MW-17 range from 3.7% to 27.2%, averaging 13.5%, and
the average volumetric water content is approximately 3% (Table 5). The permeability of the
Dakota Sandstone based on packer tests in borings installed at the site ranges from 2.71 x 10-6
cm/s to 9.12 x 10-4 cm/s, with a geometric average of 3.89 x 10-5 cm/s (TITAN, 1994).
3.1.2.2 Burro Canyon Formation
The Burro Canyon Formation, as defined by Stokes and Phoenix (1948) at its type locality near
Slick Rock, Colorado, consists of alternating conglomerate, sandstone, shale, limestone and chert
ranging in thickness from 150 to 260 feet. In the Blanding Basin, the Burro Canyon Formation
consists of deposits of alluvial and floodplain materials up to about 100 feet thick, consisting of
medium to coarse grained sandstone, conglomerate, pebbly sandstone, and claystone. Persistent,
widely traceable, conglomeratic sandstones, interpreted as deposits of a braided channel sub-
environment, occur within the formation. Sandwiched between these sandstones are variegated
mudstone units containing sandstone and siltstone lenses, the products of interchannel and
meandering channel subenvironments. Fossils collected from the Burro Canyon Formation at
various localities include freshwater invertebrates, dinosaur bones and plants. Although not truly
diagnostic, they suggest an Early Cretaceous (Aptian) age.
The average porosity of the Burro Canyon Formation is similar to that of the Dakota Sandstone.
Based on samples collected from the Burro Canyon Formation at MW-16 (abandoned, located
beneath cell 4B as shown in Figure 1A), porosity ranges from 2% to 29.1%, averaging 18.3%,
similar to the average porosity of 19% reported by MWH (MWH, 2010) for archived sandstone
samples collected from MW-23 and MW-30. Water saturations of unsaturated materials
collected from MW-16 range from 0.6% to 77.2%, and average 23.4% (Table 5).
TITAN (1994), reported that the hydraulic conductivity of the Burro Canyon Formation ranges
from 1.9 x 10-7 to 1.6 x 10-3 cm/s, with a geometric mean of 1.01 x 10-5 cm/s, based on the results
of 12 pumping/recovery tests performed in monitoring wells and 30 packer tests performed in
borings prior to 1994 (Table 4). As discussed in Section 2, subsequent testing of wells by HGC
yields a hydraulic conductivity range of approximately 2 x 10-8 to 0.01 cm/s (HGC, 2012b).
Hydraulic conductivity estimates obtained from perched wells installed and tested subsequent to
HGC (2012b) also fall within this range (HGC, 2013a; HGC, 2013b; HGC, 2014c; HGC, 2015;
HGC, 2016; HGC, 2018b; HGC, 2018c; HGC, 2019b; HGC, 2021a; and HGC, 2021b.

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In general (as discussed in Section 2.1.3), the highest permeabilities and well yields are in the
portion of the site immediately northeast and east (upgradient to cross gradient) of the TMS. A
relatively continuous, higher permeability zone (associated with poorly indurated coarser-grained
materials in the general area of the chloroform plume) has been inferred to exist in this portion of
the site (HGC, 2007b). As discussed in HGC (2004), analysis of drawdown data collected from
this zone during long-term pumping of MW-4, MW-26 (TW4-15), and TW4-19 (Figures 1A and
1B) yielded estimates of hydraulic conductivity ranging from approximately 4 x 10-5 to 1 x 10-3
cm/s (Table 3). A slug test performed at TW4-4 yielded a hydraulic conductivity of
approximately 1.7 x 10-3 cm/s (Table 1). The decrease in perched zone permeability south to
southwest of this area (south of TW4-4), based on tests at TW4-6, TW4-26, TW4-27, TW4-29
through TW4-31, and TW4-33 and TW4-34 (Table 1), indicates that this higher permeability
zone “pinches out”, consistent with the interpretation provided in HGC (2007b).
Relatively high conductivities measured at MW-11, located on the southeastern margin of the
downgradient edge of cell 3, and at MW-14, located on the downgradient edge of cell 4A, of 1.4
x 10-3 cm/s and 7.5 x 10-4 cm/s, respectively (UMETCO, 1993 and Table 4), may indicate that
this higher permeability zone extends beneath the southeastern portion of the TMS. However,
based on hydraulic tests conducted south and southwest of these wells, this zone of higher
permeability does not appear to exist within the saturated zone downgradient (south-southwest)
of the TMS. Furthermore, as discussed in HGC (2018e), although the hydraulic conductivity is
relatively high at both MW-11 and MW-14, the higher permeability materials penetrated by
these wells do not appear to connect.
Slug tests performed at groups of wells and piezometers located northeast (upgradient) of, in the
immediate vicinity of, and southwest (downgradient) of the TMS indicate generally lower
permeabilities compared with the area of the chloroform plume. The following results are based
on analysis of automatically logged slug test data using the KGS solution available in
AQTESOLV (HydroSOLVE, 2000).
Testing of TWN-series wells installed in the northeast portion of the site as part of nitrate
investigation activities (HGC, 2009) yielded a hydraulic conductivity range of approximately 3.6
x 10-7 to 0.01 cm/s with a geometric average of approximately 6 x 10-5 cm/s; including more
recently installed wells TWN-20 and TWN-21 yields a geometric average hydraulic conductivity
of approximately 5 x 10-5 cm/s. The value of 0.014 cm/s estimated for TWN-16 is the highest
measured at the site, and the value of 3.6 x 10-7 cm/s estimated for TWN-7 is one of the lowest
measured at the site.

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Testing of MW-series wells MW-23 through MW-32 (HGC, 2005) installed within and at the
margins of the TMS in 2005 (and using the higher estimate for MW-23) yielded a hydraulic
conductivity range of approximately 2 x 10-7 to 1 x 10-4 cm/s with a geometric average of
approximately 2 x 10-5 cm/s. The geometric average hydraulic conductivity of all tested MW-
series wells (including far up-gradient; far cross-gradient; and far downgradient wells; and using
the higher estimate for MW-23) is less than 3 x 10-5 cm/s.
Hydraulic tests conducted at DR-series piezometers installed as part of the southwest area
investigation (HGC 2012b) downgradient of the TMS yielded hydraulic conductivities ranging
from approximately 2 x 10-8 to 4 x 10-4 cm/s with a geometric average of 9.6 x 10-6 cm/s. The
relatively low permeabilities and shallow hydraulic gradients downgradient of the TMS result in
average perched groundwater pore velocity estimates that are among the lowest on site
(approximately 0.26 feet per year (ft/yr) to 0.91 ft/yr based on calculations presented in HGC,
2012b).
The extensive hydraulic testing of perched zone wells at the site indicates that perched zone
permeabilities are generally low with the exception of the apparently isolated zone of higher
permeability associated with the chloroform plume east to northeast (cross-gradient to
upgradient) of the TMS. The geometric average hydraulic conductivity (less than 1 x 10-5 cm/s)
of the DR-series piezometers which cover an area nearly half the size of the total monitored area
at White Mesa (excluding MW-22), is nearly identical to the geometric average hydraulic
conductivity of 1.01 x 10-5 cm/s reported by TITAN (1994), and is within the range of 5 to 10
feet per year (ft/yr) [approximately 5 x 10-6 cm/s to 1 x 10-5 cm/s] reported by Dames and Moore
(1978) for the (saturated) perched zone during the initial site investigation.
3.1.3 Mancos Shale
Conformably overlying the Dakota Sandstone is the Upper Cretaceous Mancos Shale. The
Mancos Shale was deposited in the Western Interior Cretaceous seaway (Figure 7) and is
primarily composed of uniform, dark-gray mudstone, shale, and siltstone. It was deposited in
nearshore and offshore neritic subenvironments of the Late Cretaceous Sea during its overall
southwestern transgression and subsequent northeastward regression.
The Mancos Shale was named by Cross and Purington (1899) from exposures near Mancos,
Colorado. Outcrops of the Upper Cretaceous Mancos Shale occur as hills and slopes generally
near or directly beneath overlying Quaternary pediment remnants across portions of the Blanding
Basin. Mancos Shale is absent in most of the Blanding Basin (due to erosion) where rocks of the

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Dakota Sandstone and Burro Canyon Formation are either exposed or mantled by thin
unconsolidated deposits.
The Mancos Shale in the Blanding Basin consists of marine shale and interbeds of thin (less than
2 feet thick) sandstone and siltstone beds. Various pelecypod fossils are common in Mancos
Shale outcrop areas (Huff and Lesure, 1965; Haynes et al., 1972). Total thickness is estimated at
30 to 40 feet, but is generally negligible to 20 feet, a small erosional remnant of its original
thickness of approximately 2,000 feet. The Mancos Shale was deposited during transgression and
highstand of the Cretaceous Interior Seaway during the Late Cretaceous (Elder and Kirkland,
1994). Where present, the Mancos Shale may act as an important impermeable layer reducing the
amount of potential infiltration and recharge to the underlying Dakota-Burro Canyon perched
aquifer (Avery, 1986; Goodknight and Smith, 1996).
The Mancos Shale belongs to the group of thick marine organic muds (or black shales) generally
considered to be deposited in geosynclinal areas. Bentonitic volcanic ash layers are abundant in
the Mancos Shale (Shawe, 1968). An abundance of pyrite in the layers may indicate that iron
was an important constituent of the ash, possibly being liberated by devitrification of glass and
redeposited with the diagenetic development of pyrite. Hydrogen sulfide was abundant in the
organic rich sediments accumulating at the bottom of the Mancos Sea, if it was a typical
sapropelic marine environment, as seems likely, and may have been especially abundant in the
volcanic ash (Fenner, 1933).
Trapped sea water that is buried in the mud of the Mancos Shale likely had a high content of
organic material consistent with the abundance of diagenetic pyrite. Chemical reduction resulting
from hydrogen sulfide generated in carbon-rich sediments is characteristic of stagnant sea
bottoms.
In the Early Tertiary, the original clay and silt deposited in the Mancos Shale became compacted
to about a third to a tenth of its original water saturated volume by the time it was buried to a
depth of about 10,000 feet (Shawe, 1976). Pore water throughout the Colorado Plateau, driven
from compacting mud, moved largely upward into younger sediments (Yoder, 1955), but much
water must have moved into the lower more porous strata because of local conditions of rock
structure (Hedberg, 1936), because of the relatively high water density, and because of
abnormally high fluid pressures. Expulsion of water likely occurred throughout the deposition of
the Mancos Shale in the Late Cretaceous and during deposition of younger sediments in the
Early Tertiary. Therefore expulsion occurred during a period of many millions of years and at
depths ranging from near- surface to nearly maximum depths of burial.

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Faulting occurred in many places on the Colorado Plateau, including the Blanding Basin during
the Late Cretaceous and Early Tertiary when the Mancos was undergoing deep burial by younger
strata. Faulting provided numerous avenues allowing water movement into underlying porous
strata. It seems likely therefore that the Dakota Sandstone at the base of the Mancos Shale, and
the dominantly sandy underlying Burro Canyon Formation, contained pore water which was
expelled from the Mancos and was under abnormally high fluid pressures (Shawe, 1976).
Compaction of bedding around pyrite crystals shows the early development of part of the
diagenetic pyrite, and indicates that pore fluids were being squeezed out of the Mancos Shale
during the period of diagenesis. As pore fluids became trapped in the Mancos Shale following
deposition of sediment in the Late Cretaceous, they immediately began to react with black
opaque minerals, with magnetite deposited with the abundant ash fall material and possibly with
volcanic glass and other iron-bearing material to form pyrite. Faulting that occurred on the
Colorado Plateau in the Late Cretaceous and Early Tertiary facilitated movement of the Mancos
pore water into underlying beds, causing removal of hematite coating on sand grains, destruction
of detrital black opaque minerals, and growth of iron sulfide minerals (Shawe, 1976).
3.1.4 Pyrite Occurrence in the Dakota Sandstone and Burro Canyon Formation
As discussed above, downward movement of the Mancos Shale pore water into underlying beds
of the Dakota Sandstone and Burro Canyon Formations caused removal of hematite coatings on
sand grains, destruction of detrital black opaque minerals, and the growth of iron sulfide
minerals. Shawe (1976) classifies the Dakota Sandstone and Burro Canyon Formations as
“altered-facies” rocks primarily as a result of the invasion of pore waters expelled from the
overlying Mancos Shale during compaction. Shawe states that “altered facies rocks that
developed by solution attack are notable for their almost complete loss of black opaque minerals
and gain of significant pyrite.” Shawe further states that “altered-facies rocks contain only sparse
black opaque minerals but appreciable pyrite” and that “alteration caused destruction of most
detrital back opaque minerals, precipitation of substantial pyrite, and recrystallization of
carbonate minerals that took up much of the iron liberated from the solution of black opaque
minerals.”
According to Shawe (1976), “altered-facies sandstone is light gray or, where weathered, also
light buff to light brown. It contains only a small amount of black opaque heavy minerals and
may or may not contain carbonaceous material. The light buff to light brown colors are imparted
by limonite formed from oxidation of pyrite in weathered rock.”

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Furthermore Shawe (1976) states “In weathered rocks as observed in thin sections pyrite has
been replaced by ‘limonite’, but preservation of original pyrite crystal forms and lack of
abundant limonite ‘wash’ or dustlike limonite suggest that the forms of most limonite are
indicative of the original forms of pyrite before oxidation. Pyrite (or limonite) in sandstone
occurs as isolated interstitial patches as much as 2 millimeters (mm) in diameter enclosing many
detrital grains, or as cubes 1 mm across and smaller that are mainly interstitial but that also
partially replace detrital grains.” Also “limonite pseudomorphs after marcasite have been
recognized in vugs in altered-facies sandstone of the Burro Canyon Formation.” Shawe (1976)
also notes that pyrite is more common below the water table and iron oxides (likely formed by
oxidation of pyrite) are more common in the vadose zone. These observations are consistent with
the occurrence of and oxidation of pyrite in the formations hosting the perched water at the site
as will be discussed in Section 4.
3.2 Contact Descriptions
Lithologic contacts between the Brushy Basin Member of the Morrison Formation, and between
the Dakota Sandstone and the overlying soils and/or the Mancos Shale, are described in Sections
3.2.1 and 3.2.2. Cross-sections through soils based on soil borings installed per Phase I of the
nitrate CAP are presented and discussed in Section 3.2.3.
3.2.1 Brushy Basin Member/Burro Canyon Formation Contact Elevations
Figure 8 is a contour map of the Burro Canyon Formation/Brushy Basin Member contact
generated from perched well, piezometer, DR-series boring data and the locations and elevations
of Westwater Seep and Ruin Spring. Figure 8 was generated based on data indicating that only
Westwater Seep and Ruin Spring are located at the contact between the Burro Canyon Formation
and the Brushy Basin Member (HGC, 2012b). Other seeps and springs (except Cottonwood
Seep) shown on Figure 8 occur within generally conglomeratic horizons of the Burro Canyon
Formation but at elevations above the contact with the underlying Brushy basin Member.
As discussed in HGC (2012b) examination of the area near Cottonwood Seep in July 2010 and
re-examination in October 2011 revealed no evidence for a hydraulic connection with the
perched zone. The absence of any visible seeps or anomalous vegetation in the Brushy Basin
Member east and northeast of Cottonwood Seep is consistent with dry conditions in the upper
portion of the Brushy Basin Member.
Figure 8 shows that the erosional Brushy Basin/Burro Canyon contact surface dips generally to
the south-southwest and is very irregular in the northeast portion of the site. A paleoridge in the

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Brushy Basin erosional paleosurface extends from beneath cell 4B to the southwest near
abandoned boring DR-18. To the east of this paleoridge, a paleovalley extends from south of cell
4A to the northeast, extending into the vicinity of the northern wildlife ponds. A paleovalley
subparallel to the cell 4B paleoridge is also present on the west side of the paleoridge, between
the paleoridge and the western mesa margin.
The approximate axes of these and other paleoridges and paleovalleys in the southwest portion of
the site are indicated on Figure 8. These features are especially important in this portion of the
site due to the generally small saturated thicknesses and the consequently relatively large impacts
these features are expected to have on perched water flow in this area.
Other notable features include a paleoridge surrounded by paleovalleys that trend northwest –
southeast (rather than northeast – southwest) in the area northeast of the Mill site; a paleovalley
extending from the area of cell 4B to Westwater Seep; paleovalleys converging on Ruin Spring;
and a paleoridge that appears to extend from the eastern margin of cell 4A through the vicinity of
MW-38.
3.2.2 Mancos Shale/Dakota Contact Elevations
Figures 9A through 11B are elevation contour maps of the top of bedrock (top of the Dakota
Sandstone or Mancos Shale [where present]), the top of the Dakota Sandstone, and the top of
bedrock showing Mancos thickness. Figures 9A and 9B show alternate interpretations of bedrock
elevations based on a re-interpretation of lithologic logs for the site. Specifically, Figure 9B is
based on a re-interpretation of lithologic logs (provided in Appendix A.6 and summarized in
Figure A.6) that did not specifically call out ‘Mancos Shale’ but described materials overlying
the Dakota Sandstone as having characteristics that were similar to or nearly identical to those
logged as ‘Mancos Shale’ in other borings. Two of the primary factors considered in the re-
interpretation include 1) a description of materials overlying the Dakota Sandstone as ‘shale’ or
‘silty’ or ‘sandy shale’; and 2) materials overlying the Dakota Sandstone having a strong
reactivity with dilute hydrochloric acid (HCL).
As discussed in U. S. Department of Energy (USDOE), 2011, and Shawe (1968), the carbonate
content of the Mancos is high, reaching as much as 40% and averaging 20%. This suggests that
materials overlying the Dakota at the site that react strongly with dilute HCL, even when not
specifically logged as ‘Mancos Shale’, or just ‘shale’, may at least in part be composed of
weathered Mancos due to their reactivity. In contrast to the Mancos, surficial alluvial materials
and aeolian sands are less likely to have carbonate contents as significant as the Mancos or to
react strongly with dilute HCL. In addition, logs for many borings within and at the margins of

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the TMS (in particular MW-5, MW-11, MW-12, MW-14 and MW-15) show only ‘dike material’
above the Dakota; yet Mancos Shale was likely present prior to excavating for TMS cell
construction.
The interpreted thickness of the Mancos Shale is shown in Figures 11A and 11B. Figure 11B is
based on the re-interpreted presence and thickness of the Mancos as described above and as
summarized in Figure A.6 (Appendix A.6).
The thickness of the Mancos Shale shown in Figures 11A and 11B is based on the difference
between the top of bedrock and top of Dakota Sandstone surfaces, and is clipped in areas where
erosion is expected to have removed the Mancos. Based on these maps, the top of Dakota and
top of bedrock surfaces dip generally to the south-southwest consistent with the general dip of
the top of Brushy Basin surface. In the northeast portion of the site these surfaces are generally
less irregular than the top of the Brushy Basin surface.
Notable features include a structural high in the top of Dakota and top of bedrock surfaces near
cell 4B, and a north-south trending structural high in the top of bedrock surface east to northeast
of the TMS. The latter feature is primarily the result of a ridge-like remnant of the Mancos Shale
that reaches thicknesses greater than 30 feet along the axis of the feature.
Structural highs near cell 4B are present in the top of Brushy Basin surface (Figure 8), the top of
bedrock (Figures 9A and 9B), and the top of Dakota (Figure 10) surface. These features are
ridge-like in all three surfaces but the paleoridge in the top of Brushy Basin is not coincident
with the paleoridge in the top of bedrock and top of Dakota surfaces except in the vicinity of cell
4B. The primary axis of the paleoridge in the Brushy Basin surface extends from MW-33 at the
southwest corner of cell 4B through DR-10, MW-21 and DR-18. The axis of the paleoridge in
the top of bedrock surface extends from MW-35 through DR-11, DR-15, and DR-21. The axis of
the paleoridge in the top of Dakota surface appears to extend from the vicinity of MW-24 (at the
southwest corner of cell 1) through MW-33, DR-11, and possibly DR-15 (but is less well-defined
near DR-15).
3.2.3 Soils Above the Dakota and /or Mancos
Figure 12 depicts the locations of soil borings installed near the ammonium sulfate crystal tanks
as per Phase I of the nitrate CAP (HGC, 2012a). Borings were installed to depths of refusal using
a drive-point rig as described in EFRI (2013). The depth of refusal is assumed to represent
competent bedrock. Figure 13 depicts soils cross-sections developed from these borings.

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Unconsolidated soils consist primarily of silts with interbedded sands and clays. Weathered
Mancos Shale was encountered in many of the borings. Detailed logs of all soil borings are
provided in EFRI (2013).
Soils present above the Mancos Shale in this portion of the site are dominated by the same fine-
grained materials typical of other portions of the site. Soil types encountered in borings installed
by INTERA (Appendix C) are generally consistent with those found in the vicinity of the
ammonium sulfate crystal tanks and other portions of the site.
3.3 Perched Water Elevations, Saturated Thicknesses, and Depths to
Water
As discussed in Section 2.1.3, Figure 5 is a contour map of perched water elevations generated
from fourth quarter, 2021 water level data. Figure 5 contains perched well and piezometer water
level data, and the elevations of all seeps and springs except Cottonwood Seep (for which there
is no evidence to establish a connection to the perched water system and which is located near
the Brushy Basin Member/Westwater Canyon Member contact, indicating that its elevation is
not representative of the perched potentiometric surface). Fill-in contours between the 10-foot
elevation contours are provided over portions of the site, including the area immediately west-
southwest of the TMS to allow detail in an area having relatively flat hydraulic gradients.
Figure 5 was generated assuming that each seep or spring (except Cottonwood Seep) is a known
discharge point for perched groundwater and that the elevation of the seep or spring is
representative of the perched water elevation at that location (HGC, 2010g). As discussed in
Section 2.1.4, because of the presence of cottonwoods, perched groundwater elevations near
seeps/springs that are dry for portions of the year are likely to be near the surface.
Figure 14 shows the saturated thicknesses of the perched zone based on fourth quarter, 2021
water level data. Saturated thicknesses range from approximately 81 feet at TWN-18, located
just north of the Mill site (and adjacent to the historic pond), to less than 5 feet in the southwest
portion of the site, downgradient of the TMS. A saturated thickness of approximately 2 feet
occurs in well MW-34 along the south dike of cell 4B, and the perched zone has been
consistently dry at MW-33 located at the southwest corner of cell 4B, and at MW-21 located
south-southwest of cell 4B. Abandoned well MW-16 (formerly located beneath cell 4B as shown
in Figure 1A) was also consistently dry. MW-21, MW-33 and abandoned well MW-16 are all
located on a structural high in the top of Brushy Basin Member surface (Figure 8).

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Figure 15 shows depths to perched water as of the fourth quarter of 2021. Depths to perched
water range from approximately 42 feet below top of casing (btoc) northeast of the TMS (at
TWN-3, adjacent to the historical pond) to approximately 114 feet btoc at the southwestern
margin of cell 3. Prior to cessation of water delivery to the northern wildlife ponds the shallowest
depths to water were encountered in piezometers and wells near these ponds.
3.4 Interpretation of Cross-Sections
Lithologic and soils cross-sections prepared for various portions of the site are discussed in the
following Sections. In general, the lithologies encountered in the borings used to construct the
cross-sections are consistent with the literature and with past investigations at the site (prior to
TITAN, 1994). Figures 16A, 16B, 17, 18A, 18B, and 19 are lithologic and perched groundwater
elevation cross-sections covering various areas of the site.
3.4.1 Central and Northeast Areas
Figures 16A, 16B and 17 are lithologic cross-sections in the central to northeast portions of the
site, as shown on Figure 1A. Figure 16A is a northeast-southwest oriented cross-section (NE-
SW) extending from abandoned well MW-3 to TWN-12. Figure 16B is a parallel cross section
(NE2-SW2) extending from TWN-18 to TWN-19. Figure 17 is a northwest-southeast cross-
section (NW-SE) extending from TWN-7 to abandoned piezometer Piez-3. Figures 16A, 16B,
and 17 indicate site features located near the cross-sections.
These cross-sections indicate that the top of Brushy Basin surface is irregular in the northeast
portion of the site and that, as discussed in Sections 3.1.2.1 and 3.1.2.2, the Burro Canyon
Formation and Dakota Sandstone contain shale/claystone and conglomerate interbeds of varying
thickness and continuity. Where poorly indurated (poorly cemented), coarser sand and
conglomeratic horizons are expected to be relatively permeable; shale/claystone horizons are
expected to be at least partial barriers to perched groundwater flow, and where present in the
vadose zone, to represent at least partial barriers to downward percolation of recharge. That local
saturated conditions have not been encountered above shale/claystone horizons during drilling
within the Dakota Sandstone and Burro Canyon Formations suggests that recharge rates over
most of the site are generally low, except near unlined ponds or surface depressions, or other
areas having enhanced recharge due to their locations within drainages or due to relatively flat,
slowly drainable topography.
Figure 16A, 16B and 17 show that the perched water table surface remains relatively elevated in
the vicinities of the northern wildlife ponds and the historical pond. TWN-2 and TWN-3 (Figure

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1B) are located within and adjacent to the footprint of the historical pond, respectively. TWN-2
is a nitrate pumping well and TWN-3 a non-pumping nitrate monitoring well. As will be
discussed in Section 3.5.2, the water level at TWN-2 remained persistently high for many years
after installation, likely as a result of low permeability and possibly enhanced recharge in the
vicinity due to graded areas of the Mill site having relatively flat topography and relatively slow
runoff. Although the water level at TWN-3 remains relatively elevated, the water level at TWN-2
has declined due to pumping.
3.4.2 Southwest Area
Figures 18A, 18B and 19 are cross-sections showing the hydrogeology of the perched zone in the
area southwest of the TMS located as shown in Figure 1A. Figure 18A provides west-east cross-
sections (W-E and W2-E2) across the area immediately west and southwest of cell 4B. Figure
18B is a west-northwest to east-southeast (WNW to ESE) cross section (from DR-7 to MW-17)
that extends along the south dikes of TMS cells 4A and 4B. Figure 19 is a south-north cross-
section (S-N) from the south dike of cell 4B to Ruin Spring. Cross-sections W-E and S-N are
oriented generally parallel to perched water flow; and W2-E2 and WNW-ESE are oriented
generally perpendicular to perched water flow. Figure 18B (WNW-ESE) shows that MW-33 is
dry and the saturated thickness at MW-34 is small due to the structural high in the top of the
Brushy Basin surface that trends through MW-21 and MW-33.
Except for abandoned DR-series borings, water levels in the cross sections are based on fourth
quarter, 2021 data. Water levels for abandoned DR-series borings are from the second quarter,
2011. Water levels for DR-series piezometers have not changed significantly between the third
quarter of 2011 and the fourth quarter of 2021 (as shown in Figure 20) suggesting that second
quarter, 2011 water levels for abandoned DR-series borings are likely still representative of
current conditions.
As shown in Figure 14, cross-sections W-E and W2-E2 in Figure 18A, and cross section S-N in
figure 19, the saturated thickness of the perched zone in the southwest area of the site varies from
negligible to more than 20 feet. The variable saturated thickness has implications regarding the
flow of perched water to known discharge points Westwater Seep and Ruin Spring. Perched
water moving downgradient from the vicinity of the TMS westward toward abandoned boring
DR-2 must pass through a region of small saturated thickness occupied by DR-6 and DR-7
(Figures 5, 14 and 18A). By Darcy’s Law, downgradient areas affected by groundwater
discharge points such as Westwater Seep and Ruin Spring that have larger saturated thicknesses
must receive local recharge from precipitation because the water supplied by lateral perched flow
is inadequate to maintain the large saturated thicknesses in these areas.

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Two areas of relatively large saturated thickness that are downgradient of areas of small
saturated thickness are of particular interest: the area near DR-2 (abandoned) and DR-5 located
west of the area near DR-6 and DR-7 as shown in Figure 18A (cross-section W-E), and the area
near DR-25 located south of the area near MW-20 as shown in Figure 19 (cross-section S-N).
Each of the above areas of larger saturated thickness is downgradient of the corresponding area
of small saturated thickness, and each downgradient area of larger saturated thickness is affected
by a perched water sink or discharge point. The primary known perched groundwater discharge
point or sink downgradient of DR-2 (abandoned) and DR-5 are Westwater Seep to the northeast
and the paleovalley leading south to Ruin Spring (Figures 8 and 14). The primary discharge point
near abandoned boring DR-25 is Ruin Spring. Lateral flow from areas of larger saturated
thickness that may exist to the east of cross-section S-N may supply the water needed to maintain
the relatively large saturated thickness near DR-25. However, the reported temporary increases
in flow from Ruin Spring (and Westwater Seep) after precipitation events (HGC, 2010g) are
problematic unless flow is temporarily enhanced by local recharge.
As discussed in HGC (2010g), enhanced local recharge is likely near the mesa margins where
weathered Dakota Sandstone and Burro Canyon Formation are exposed by erosion (Figure E.2,
Appendix E). Lithologic Logs at DR-2 and DR-5 (Appendix A) show only a few feet of
unconsolidated material above the Dakota Sandstone and visual inspection of the mesa near DR-
2 (abandoned) and DR-5 shows that weathered Dakota is often exposed (consistent with the
geology presented in Dames and Moore (1978). Due to the thin veneer of unconsolidated
material overlying the Dakota Sandstone, and thin, weathered or absent Mancos Shale, recharge
near DR-2 and DR-5 (cross-section W-E, Figure 18A) will be facilitated. Similarly, in the area
near abandoned boring DR-25 and Ruin Spring, recharge will be facilitated by the topography,
the thinness or absence of the Mancos Shale, and the surface exposure of the Dakota Sandstone
and Burro Canyon Formation between DR-25 and Ruin Spring (cross-section S-N, Figure 19).
3.5 Perched Water Occurrence and Flow
Description of the occurrence and flow of perched water at the site focuses on three general
areas: 1) the nitrate investigation area, 2) the vicinity of the chloroform plume, and 3) areas
beneath and downgradient of the TMS, as per Sections 3.5.2, 3.5.3, and 3.5.4 respectively.
3.5.1 Overview
As discussed in Section 2.1.3, perched groundwater at the site occurs primarily within the Burro
Canyon Formation as well as the overlying Dakota sandstone where saturated thicknesses are
greater. Perched water flow is generally from northeast to southwest across the site. Flow onto

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the site occurs as underflow from areas northeast of the Mill site where perched zone saturated
thicknesses are generally greater. Flow exits the Mill property in seeps and springs to the east,
west, southwest and southeast. Any flow that does not discharge in seeps or springs presumably
exits as underflow to the southeast of Ruin Spring, along the southwest extending lobe of White
Mesa located between Ruin Spring and Corral Springs (Figure 1B).
3.5.1.1 General Site Flow Pattern
Fourth quarter 2021 perched water elevations (Figure 5) show the typical west-southwesterly to
south-southwesterly flow pattern at the site. The historic water level contour maps in Appendix
D demonstrate the persistence of the generally southwesterly perched flow pattern. As noted
previously, the Appendix D maps do not incorporate seep and spring elevations.
As discussed in Section 2.1.3, beneath and downgradient of the TMS, on the west side of the site,
perched water flow is south-southwest to west-southwest. On the eastern side of the site perched
water flow is generally southerly to south-southwesterly. Perched zone hydraulic gradients
currently range from a maximum of nearly 0.098 feet per foot (ft/ft) east of cell 2 (in the vicinity
of the chloroform plume, between TW4-2 and TW4-3) to approximately 0.0021 ft/ft in the
northeast corner of the site (between TWN-19 and TWN-16). Hydraulic gradients in the
southwest portion of the site are typically close to 0.01 ft/ft, but the gradient is less than 0.005
ft/ft to the west-southwest of cell 4B, between cell 4B and DR-8. The overall average site
hydraulic gradient, between TWN-19 in the extreme northeast to Ruin Spring in the extreme
southwest, is approximately 0.011 ft/ft.
Perched groundwater discharges in springs and seeps along the mesa margins. These features are
located along Westwater Creek Canyon and Cottonwood Canyon to the west and southwest of
the site, and along Corral Canyon to the east of the site, where the Burro Canyon Formation is
exposed. Based on the data presented in Figure 5, the discharge points located most directly
downgradient of the TMS are Westwater Seep and Ruin Spring. Westwater Seep is located
approximately 2,200 feet west, and Ruin Spring is located approximately 9,400 feet south-
southwest, of the existing TMS (Figure 1B).
Dry areas beneath cell 4B and southwest of cell 4B (south of MW-21) affect perched water flow
and are defined in Figure 5 by areas where the kriged contact between the Burro Canyon
Formation and the Brushy Basin Member is higher in elevation than the kriged perched
groundwater elevation. The dry areas shown in Figure 5 encompass abandoned dry well MW-16,
dry well MW-21, dry well MW-33, and abandoned dry boring DR-18. The areas defined by the
heavy yellow dashed contour lines have saturated thicknesses estimated to be less than 5 feet. As

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shown in Figure 5 and southwest area cross-sections (Figures 18A, 18B and 19), a large portion
of the perched zone west and southwest (downgradient) of the TMS has a saturated thickness
less than 5 feet. This zone has been persistent based on measurements since the third quarter of
2011. An apparent perched groundwater divide exists in the vicinity of DR-2 (abandoned, Figure
1A) and DR-5 (Figure 5). Perched water north of this apparent divide is expected to flow
primarily northeast toward Westwater Seep and perched water south of this apparent divide is
expected to flow primarily south toward Ruin Spring (as will be discussed in Section 3.5.4).
Figure 14 shows the axes of paleoridges and paleovalleys in the Brushy Basin Member erosional
paleosurface and posted fourth quarter, 2021 saturated thicknesses. As indicated, paleoridges in
the southwest area of the site are associated with dry areas and with areas of low saturated
thicknesses; paleovalleys are associated with areas of higher saturated thicknesses. Westwater
Seep and Ruin Spring are located in paleovalleys. The average saturated thickness based on
measurements at MW-35, DR-7, and DR-6, which are the points closest to a line between the
southwest portion of cell 3 and Westwater Seep, is less than 6 feet. The average saturated
thickness based on measurements at MW-37, DR-13, MW-3A, MW-20, and DR-21, which lay
close to a line between the southeast portion of cell 4B and Ruin Spring, is approximately 11
feet.
Perched groundwater mounding associated with the wildlife ponds locally changes the generally
southwesterly perched water flow patterns. For example, northeast of the Mill site, relict
mounding associated with the northern wildlife ponds results in locally northwesterly flow near
PIEZ-1. Mounding also causes the hydraulic gradient to be more westerly west of the ponds and
more easterly east of the ponds. The impact of the mounding associated with the northern ponds,
to which water has not been delivered since March 2012, continues to diminish as the mound
decays due to reduced recharge. Similarly, the impact of mounding associated with the southern
wildlife pond is diminishing due to reduced recharge. As discussed in Section 2.1.3, since the
first quarter of 2012, water levels have declined within the northern mound by as much as 25 feet
(at PIEZ-2), and within the southern mound by as much as 23 feet (at PIEZ-5).
3.5.1.2 Influence of Pumping and Wildlife Pond Seepage on Flow and Dissolved
Constituent Concentrations
Figures 1A and 1B show the locations of chloroform and nitrate pumping wells at the site. MW-
4, MW-26, TW4-1, TW4-2, TW4-4, TW4-11, TW4-19, TW4-21, TW4-37, TW4-39, TW4-40
and TW4-41 are chloroform pumping wells; and TWN-2, TW4-22, TW4-24, and TW4-25 are
nitrate pumping wells. TW4-20 was formerly a chloroform pumping well, but due to collapse
during August, 2020, was abandoned in October, 2020. As discussed in HGC (2022), the

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abandonment of TW4-20 had little or no impact on the effectiveness of the chloroform pumping
system in this area.
Figure 21 is a map showing kriged fourth quarter 2021 perched water levels, the extents of the
nitrate and chloroform plumes at the site, and inferred perched water flow paths. Figure 22 is a
detail map showing the locations of perched wells, fourth quarter, 2021 kriged water levels, and
inferred capture zones associated with pumping wells.
As discussed in Section 2, four additional chloroform wells, TW4-40 through TW4-43, were
installed during February, 2018 (HGC, 2018b); April, 2019 (HGC, 2019b); and September, 2021
(HGC, 2021b). TW4-40 was installed approximately 200 feet south of TW4-26; TW4-41 was
installed immediately north-northeast of TW4-4; TW4-42 was installed approximately 200 feet
south of TW4-40; and TW4-43 was installed approximately 200 feet east-southeast of TW4-30.
TW4-41 was designed as a pumping well to augment chloroform mass removal in the southern
portion of the plume; and TW4-40 was converted into a pumping well to control chloroform
migration in the southern extremity of the plume. TW4-40 primarily controls elevated
chloroform detected at both TW4-40 and TW4-26 (located immediately up-gradient of TW4-40).
As described in HGC (2012a) the nitrate pumping system, which became operational in the first
quarter of 2013, is designed to (eventually) establish hydraulic capture of the nitrate plume
upgradient (north of) TW4-22 and TW4-24. MW-30 and MW-31, located at the downgradient
edge of the plume, are not pumped in order to minimize the potential for downgradient
chloroform migration. As described in HGC (2007b) and HGC (2022), the chloroform pumping
system, which became operational in 2003 with the pumping of MW-4, TW4-19, and MW-26
(TW4-15), and later enhanced by the addition of TW4-20 in 2005; TW4-4 in 2010; TW4-1,
TW4-2, TW4-11, TW4-21, and TW4-37 in 2015; TW4-39 in 2016; and TW4-41 in 2018, is
designed primarily to reduce mass in upgradient portions of the plume where saturated
thicknesses, concentrations, and well productivities are higher. Mass reduction is thereby
maximized, the source of chloroform to downgradient areas cut off, and natural attenuation
facilitated. As discussed above, the addition to the pumping system in 2019 of well TW4-40,
which is located in the southern extremity of the plume, helps to control elevated chloroform
detected at both TW4-40 and TW4-26. TW4-40 is valuable in that it is located within the
downgradient (southern) toe of the plume and is relatively productive. Pumping of TW4-40 is
likely to more effectively reduce or prevent further downgradient plume migration than can be
expected by pumping at the more upgradient locations.
Local depression of the perched water table occurs near chloroform pumping wells MW-4, MW-
26, TW4-1, TW4-2, TW4-11, TW4-19, TW4-21, TW4-37, TW4-39, TW4-40 and TW4-41

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(Figure 22). Pumping of chloroform wells MW-4 and TW4-19 began in 2003 (HGC, 2004).
Well-defined cones of depression are evident near all chloroform pumping wells except TW4-37,
which began pumping during 2015. The lack of a well-defined cone of depression near TW4-37
is likely due to its close proximity to chloroform and nitrate pumping wells TW4-19 and TW4-
22.
Although operation of chloroform pumping well TW4-4 depressed the water table in the vicinity
of TW4-4, a well-defined cone of depression was not clearly evident until adjacent well TW4-41
began pumping in 2018. The former lack of a well-defined cone of depression near TW4-4 likely
resulted from 1) variable permeability conditions in the vicinity of TW4-4, and 2) persistent
relatively low water levels at adjacent well TW4-14, as will be discussed in Section 3.5.3.
Local depression of the perched water table also occurs near nitrate pumping wells TWN-2,
TW4-22, TW4-24, and TW4-25 (Figure 22), which are operated to reduce nitrate mass in the
perched groundwater as per the nitrate CAP (HGC, 2012a). Although TWN-2 has been pumping
as long as the other nitrate pumping wells, the cone of depression now associated with this well
was formerly masked by its location on the edge of a perched groundwater mound. Cones of
depression are likely to still be in the process of development in the vicinities of the four nitrate
pumping wells which were brought on-line in the first quarter of 2013. Relatively slow
development of capture zones has been expected due to generally low permeability within the
nitrate plume.
The hydraulic effects of the chloroform and nitrate pumping systems overlap. Figure 22 shows
the inferred capture of both chloroform and nitrate pumping systems as of the fourth quarter of
2021. Capture zones are calculated by hand based on the kriged water level contours following
the rules for flow nets. From each pumping well, stream tubes that bound the capture zone are
reverse-tracked, and perpendicularity is maintained between each stream tube and the intersected
kriged water level contours.
Recharge from the wildlife ponds has impacted perched water elevations and flow directions at
the site by creating perched groundwater mounds as discussed in Section 3.5.1. Furthermore, the
March 2012 cessation of water delivery to the northern ponds, which are generally upgradient of
the nitrate and chloroform plumes at the site, has resulted in changing conditions that were
expected to impact constituent concentrations and migration rates within the plumes.
Specifically, past recharge from the ponds has helped limit many constituent concentrations
within the plumes by dilution while the associated groundwater mounding has increased
hydraulic gradients and contributed to plume migration. Since use of the northern ponds was
discontinued in March 2012, increases in constituent concentrations in many wells, and

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decreases in hydraulic gradients within the plumes, are attributable to reduced recharge and the
decay of the associated groundwater mound.
The impacts associated with cessation of water delivery to the northern wildlife ponds were
expected to propagate downgradient (south and southwest) over time. Wells close to the ponds
were generally expected to be impacted sooner than wells farther downgradient of the ponds.
Therefore, constituent concentrations were generally expected to increase in downgradient wells
close to the ponds before increases were detected in wells farther downgradient of the ponds.
Although such increases were anticipated to result from reduced dilution, the magnitude and
timing of the increases have been difficult to predict due to the complex permeability distribution
at the site and factors such as pumping and the rate of decay of the perched groundwater mound.
The potential exists for some wells completed in higher permeability materials to be impacted
sooner than some wells completed in lower permeability materials even though the latter may be
closer to the ponds. Localized increases in concentrations of constituents such as chloroform and
nitrate within and near the chloroform plume, and of nitrate and chloride within and near the
nitrate plume, may occur even when these plumes are under control. Ongoing mechanisms that
can be expected to increase constituent concentrations locally as a result of reduced wildlife pond
recharge include but are not limited to:
1. Reduced dilution - the mixing of low constituent concentration pond recharge into
existing perched groundwater will be reduced over time.
2. Reduced saturated thicknesses – dewatering of any higher permeability layers receiving
primarily low constituent concentration pond water will result in wells intercepting these
layers receiving a smaller proportion of the low constituent concentration water.

The combined impact of the above two mechanisms was considered to be especially likely at
chloroform and nitrate pumping wells and non-pumped wells adjacent to the pumped wells. The
expected overall impact was generally higher constituent concentrations in chloroform and
nitrate wells over time until mass reduction resulting from pumping and natural attenuation
eventually reduced concentrations. Short-term changes in concentrations at pumping wells and
wells adjacent to pumping wells are also expected to result from changes in pumping conditions.
In general, due to its closer proximity to the wildlife ponds, reduced dilution has impacted wells
within and adjacent to the chloroform plume to a greater extent than wells located within and
adjacent to the nitrate plume. However, between the third quarter of 2018 and first quarter of 2021,
continued pumping, natural attenuation, and the diminishing effects of reduced recharge from the
wildlife ponds, have caused chloroform concentrations at several of the chloroform wells, in
particular TW4-6, TW4-8, TW4-9 and TW4-33, to drop below 70 µg/L. Prior to dropping below

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70 µg/L, these four wells were either already within the chloroform plume; or had been re-
incorporated into the plume after cessation of water delivery to the wildlife ponds.
3.5.2 Nitrate Investigation Area
The extent of the nitrate plume addressed by the nitrate CAP (HGC, 2012a) and referred to as the
‘nitrate plume’ (defined by nitrate as nitrogen concentrations exceeding 10 mg/L) is shown in
Figure 21. Figure 21 also displays kriged fourth quarter, 2021 perched water level contours and
inferred flow paths and shows the extent of the chloroform plume which overlaps the nitrate
plume in the vicinity of TW4-22. Nitrate exceeding 10 mg/L also occurs to the southeast of the
plume in relatively isolated pockets (for example, near TW4-27). As discussed in HGC (2014a),
this southeastern nitrate is attributed to sanitary leach field discharge associated with the
chloroform plume and potentially with former cattle ranching operations at the site. Nitrate
exceeding 10 mg/L far to the south and southwest at MW-20 and MW-38 is also potentially
associated with former cattle ranching operations. The potential for cattle to contribute nitrate to
soil is discussed in McFarland et al (2006). Elevated nitrate in soil can then act as a source to
groundwater.
Perched groundwater flow within the area of the nitrate plume varies from south-southwest to
west-southwest. The generally southwesterly hydraulic gradient typical of the majority of the site
is influenced by past recharge from the northern wildlife ponds; elevated water levels in the
vicinity of well TWN-3; and formerly elevated water levels at pumping well TWN-2. TWN-2 is
within the footprint of the historical pond and TWN-3 is immediately east of the footprint of the
pond, as shown in Figure 1B. Recharge from the northern wildlife ponds, located immediately
northeast of the nitrate plume, caused a shift in gradient in the northern portion of the plume
from southwesterly to west-southwesterly (compare Appendix D 1990 and 1994 water level
maps with Figure 21). The persistently elevated water level that formerly existed at TWN-2,
which has functioned as a nitrate pumping well since the first quarter of 2013, likely resulted
from low permeability and possibly enhanced recharge in the vicinity of TWN-2 due to graded
areas of the Mill site having relatively flat topography and relatively slow runoff.
Cones of depression associated with nitrate pumping wells TW4-22, TW4-24, TW4-25, and
TWN-2, have been developing since initiation of pumping during the first quarter of 2013.
Hydraulic capture associated with these wells has developed slowly due to low permeability
conditions. That sufficient capture will eventually develop is indicated by calculations presented
in HGC (2017) showing that nitrate pumping exceeds pre-pumping flow through the nitrate
plume by a factor of approximately 2.1; and calculations presented in EFRI (2022c) showing that
as of the fourth quarter of 2021, pumping at nitrate wells, and at chloroform wells within the

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nitrate plume (TW4-19, TW4-21 and TW4-37), exceeds pre-pumping flow through the plume by
a factor of 2.3.
Water level patterns near nitrate pumping wells have been influenced by the presence of, and the
decay of, the groundwater mound associated with the northern wildlife ponds, and by the
persistent relatively low water level elevation that formerly existed at TWN-7. In addition, water
level patterns near nitrate pumping wells are influenced by interaction with nearby chloroform
pumping wells. The long term interaction between nitrate and chloroform pumping systems
continues to evolve.
Criteria regarding control and potential migration of the nitrate plume are detailed in the nitrate
CAP (HGC, 2012a). As stated in the CAP, MW-5, MW-11, MW-30, and MW-31 are located
downgradient of TW4-22 and TW4-24; MW-30 and MW-31 are within the nitrate plume near its
downgradient edge; and MW-5 and MW-11 are outside of and downgradient of the plume. Per
the CAP, hydraulic control based on concentration data is considered successful if the
concentrations of nitrate in MW-30 and MW-31 remain stable or decline, and concentrations of
nitrate in downgradient wells MW-5 and MW-11 do not exceed the 10 mg/L standard. Based on
these criteria, the nitrate plume is under control.
The plume has not migrated downgradient to MW-5 or MW-11 because nitrate exceeding 10
mg/L has not been detected at MW-11 and has been detected at concentrations less than 1 mg/L
at MW-5. Nitrate concentrations in both MW-30 and MW-31 at the downgradient edge of the
plume have been relatively stable, demonstrating that plume migration is minimal (HGC, 2017;
EFRI, 2022c). Recent increases in nitrate at downgradient well MW-11 suggest that
downgradient migration continues to occur but at a low rate.
As discussed in Section 2, elevated chloride (exceeding 100 mg/L) commingles with the nitrate
plume. Chloride has been increasing at MW-31; and is also increasing at MW-30 (but at a lower
rate). Increasing chloride at both MW-30 and MW-31 is consistent with ongoing downgradient
migration of the nitrate/chloride plume (EFRI, 2022c). The increases in chloride and stable
nitrate at MW-30 and MW-31 suggest a natural attenuation process that is affecting nitrate but
not chloride. A likely process that would degrade nitrate but leave chloride unaffected is
reduction of nitrate by pyrite. The likelihood of this process in the perched zone is discussed in
HGC (2012c) and HGC (2017). Estimated natural nitrate degradation rates range from
approximately 172 pounds per year (lb/yr) to 200 lb/yr as discussed in HGC (2017). Based on
these rates, less than 200 years would be required to remediate the nitrate plume, even in the
absence of any direct mass removal by pumping.

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Understanding of perched water level behavior in the area northeast (upgradient) of the Mill site
was enhanced by the installation of TWN-series wells TWN-1 through TWN-19 within and
northeast of the nitrate plume in 2009; and by the installation of TWN-20 and TWN-21 to the
west of the nitrate plume during the second quarter of 2021. Prior to the installation of TWN-
series wells, upgradient information was limited to that provided by MW-1, MW-18, MW-19,
PIEZ-1, and PIEZ-2. As shown in Figure 1B, nitrate wells TWN-5, TWN-8, TWN-9, TWN-10,
TWN-11, TWN-12, TWN-13, TWN-15, and TWN-17 have been abandoned as per the nitrate
CAP.
TWN-20 and TWN-21 were installed in response to nitrate exceeding 10 mg/L at TWN-7
(Figure 1B), which was historically located downgradient of the northern extremity of the nitrate
plume defined by wells TWN-2 and TWN-3. Although measurements at TWN-20 and TWN-21
provide additional detail on water level distributions in this area, no significant changes to water
level contours north of cell 1 resulted from water level measurements at these wells.
In general, water level data provided by the TWN-series wells and existing wells and
piezometers in the northeast portion of the Mill property indicate that perched water flow is to
the southwest. Data from many of these wells helped to better define the extent of the perched
groundwater mound resulting from former recharge at the northern wildlife ponds. Figure 23 is a
water level contour map from the fourth quarter, 2011 constructed prior to both TWN well
abandonment and cessation of water delivery to the wildlife ponds. Comparing Figure 23 with
Figure 5 demonstrates the substantial reductions in the perched groundwater mounds associated
with the wildlife ponds between the fourth quarters of 2011 and 2021.
3.5.3 Vicinity of Chloroform Plume
As noted in Section 3.5.1.2, the footprint of the chloroform plume is shown in Figure 21. The
plume boundary is defined by the Groundwater Corrective Action Limit (GCAL) of 70 µg/L.
Water level and concentration data presented in this Section are from EFRI (2022b) or HGC
(2022) unless otherwise indicated.
Perched groundwater flow within the area of the chloroform plume has been generally southerly
to southwesterly. The chloroform plume resulted from disposal of laboratory wastes to the
abandoned scale house and former office sanitary leach fields. The abandoned scale house leach
field is the likely source of the southeastern portion of the plume and the former office leach
field is the likely source of the northwestern portion of the plume (HGC, 2007b). Both of these
sources received laboratory wastes prior to operation of the TMS (circa 1980), and in the case of
the abandoned scale house leach field, prior to construction of the Mill. Laboratory wastes prior

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to 1980 were first disposed to the abandoned scale house leach field and later to the former office
leach field. Laboratory wastes have been disposed to the TMS since it became operational circa
1980.
The abandoned scale house leach field was located immediately north-northwest of well TW4-18
(Figure 1B). Historic perched water flow in this area was generally to the south (Appendix D).
Chloroform disposed in the abandoned scale house leach field migrated primarily southerly to
the vicinity of well MW-4 where it was detected in 1999. Hydraulic gradients and flow
directions in this area were impacted by pre-2012 recharge from the northern wildlife ponds
located north of MW-4.
The former office leach field is located in the immediate vicinity of chloroform pumping well
TW4-19 and immediately northeast of cell 2 (and former chloroform pumping well TW4-20,
now abandoned) [Figure 1B]. Perched water flow in this area was historically southwest
(Appendix D), and hydraulic gradients were enhanced by pre-2012 recharge from the northern
wildlife ponds (located to the northeast).
Once chloroform pumping began in 2003 the flow regime, formerly dominated by wildlife pond
recharge in the vicinity of the chloroform plume, began to change locally under the influence of
the pumping. Reduced wildlife pond recharge since the first quarter of 2012 and the initiation of
nitrate pumping in the first quarter of 2013 have also impacted the flow regime.
Well defined cones of depression are evident in the vicinity of all chloroform pumping wells
except TW4-37, which began pumping during 2015. The lack of a well-defined cone of
depression near TW4-37 is likely due to its close proximity to chloroform pumping well TW4-19
and nitrate pumping well TW4-22. Prior to pumping at adjacent well TW4-41, a well-defined
cone of depression was not evident at TW4-4. The former lack of a well-defined cone of
depression near TW4-4 had causes other than proximity of other pumping wells, although once it
began pumping in 2010, TW4-4 has depressed the water table in the vicinity of TW4-4.
As discussed in Section 3.5.1.2 variable permeability conditions likely contributed to the former
lack of a well-defined cone of depression near chloroform pumping well TW4-4. Changes in
water levels at wells immediately south of TW4-4 resulting from TW4-4 pumping were expected
to be muted because TW4-4 is located at a transition from relatively high to relatively low
permeability conditions south (downgradient) of TW4-4. The permeability of the perched zone at
TW4-6, TW4-26, and TW4-29 is approximately two orders of magnitude lower than at TW4-4
(Table 1). In addition, drawdown of water levels at wells immediately south of TW4-4 resulting

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from TW4-4 pumping was difficult to determine because of the general increase in water levels
that formerly occurred in this area due to past recharge from the wildlife ponds.
Water levels at TW4-4 and TW4-6 increased by nearly 2.7 and 2.9 feet, respectively, between
the fourth quarter of 2007 and the fourth quarter of 2009 (just prior to the start of TW4-4
pumping) at rates of approximately 1.2 feet/year and 1.3 feet/year, respectively. However, the
increase in water level at TW4-6 was reduced after the start of pumping at TW4-4 (first quarter
of 2010) to approximately 0.5 feet/year suggesting that TW4-6 is within the hydraulic influence
of TW4-4 (Figure 24).
Except for TW4-30, which was incorporated into the chloroform plume in the fourth quarter of
2020, water levels in wells currently within the chloroform plume south of TW4-4 (TW4-26,
TW4-29, and TW4-40) have been trending generally downward since the fourth quarter of 2013.
This downward trend is attributable to both the cessation of water delivery to the wildlife ponds
and pumping. Prior to 2018, generally increasing water levels were confined to some of the wells
marginal to the chloroform plume such as TW4-14, TW4-27, TW4-30, and TW4-31. Water
levels in these marginal wells, and TW4-30, have since stabilized.
These spatially variable water level trends likely result from pumping conditions, the
permeability distribution, and distance from the wildlife ponds. Wells that are relatively
hydraulically isolated (due to completion in lower permeability materials or due to intervening
lower permeability materials) and that are more distant from pumping wells and the wildlife
ponds, are expected to respond more slowly to pumping and reduced recharge than wells that are
less hydraulically isolated and are closer to pumping wells and the wildlife ponds. Wells that are
more hydraulically isolated will also respond more slowly to changes in pumping.
The former lack of a well-defined cone of depression at TW4-4 was also influenced by the
former, relatively low water level at non-pumping well TW4-14, located east of TW4-4 and
TW4-6. Since pumping began at TW4-41, however, water levels at TW4-14 have generally been
higher than water levels at TW4-4. For the fourth quarter of 2021, the water level at TW4-14
(approximately 5535.7 ft amsl) is nearly 6 feet higher than the water level at TW4-6
(approximately 5529.8 ft amsl) and more than 5 feet higher than the water level at TW4-4
(approximately 5530.3 ft amsl), consistent with a substantial cone of depression.
The water levels at wells TW4-14 and downgradient well TW4-27 (installed south of TW4-14 in
the fourth quarter of 2011) were similar (within 1 to 2 feet) until the third quarter of 2014; both
appeared anomalously low. TW4-27 was positioned at a location considered likely to detect any
chloroform present and/or to bound the chloroform plume to the southeast and east (respectively)

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of TW4-4 and TW4-6. Groundwater data collected since installation indicates that TW4-27 does
indeed bound the chloroform plume to the southeast and east of TW4-4 and TW4-6
(respectively); however chloroform exceeding 70 µg/L was detected at more recently installed
temporary perched wells TW4-29 (located south of TW4-27) and TW4-33 (located between
TW4-4 and TW4-29). Note that, although chloroform at TW4-33 exceeded 70 µg/L through
2020, concentrations dropped below 70 µg/L after the fourth quarter of 2020.
Prior to the installation of TW4-27, the former (pre-TW4-41 pumping), persistently low water
level at TW4-14 was considered anomalous because it appeared to be downgradient of all three
wells TW4-4, TW4-6, and TW4-26, yet chloroform had not been detected at TW4-14.
Chloroform had apparently migrated from TW4-4 to TW4-6 and from TW4-6 to TW4-26. This
suggested that TW4-26 was actually downgradient of TW4-6, and TW4-6 was actually
downgradient of TW4-4, regardless of the flow direction implied by the low water level at TW4-
14. The water level at TW4-26 (5527.8 feet amsl) is, however, lower than water levels at
adjacent wells TW4-6 (5529.8 feet amsl), and TW4-23 (5531.8 feet amsl).
Hydraulic tests indicate that the permeability at TW4-27 is an order of magnitude lower than at
TW4-6 and three orders of magnitude lower than at TW4-4 (Table 1). Past similarity of water
levels at TW4-14 and TW4-27, and the low permeability estimate at TW4-27, suggested that
both wells were completed in materials having lower permeability than nearby wells. The low
permeability condition likely reduced the rate of long-term water level increase at TW4-14 and
TW4-27 compared to nearby wells, yielding water levels that appeared anomalously low. This
behavior is consistent with hydraulic test data collected from more recently installed wells TW4-
29, TW4-30, TW4-31, TW4-33, TW4-34 and TW4-35, which indicate that the permeability of
these wells is one to two orders of magnitude higher than the permeability of TW4-27 (Table 1).
Hydraulic tests also indicate that the permeability at TW4-36 is slightly higher than but
comparable to the low permeability at TW4-27, suggesting that TW4-36, TW4-14 and TW4-27
are completed in a continuous low permeability zone.
The fourth quarter, 2021 water level at TW4-27 (approximately 5529.1 ft. amsl) is more than 6
1/2 feet lower than the water level at TW4-14 (5535.7 ft. amsl). Increases in water level
differences between TW4-14 and TW4-27 since 2013 are attributable to more rapid increases in
water levels at TW4-14 compared to TW4-27. This behavior likely results primarily from: the
relative positions of the wells; past water delivery to the northern wildlife ponds; and the
permeability distribution. Past seepage from the ponds caused propagation of water level
increases in all directions including downgradient to the south. The relative hydraulic isolation of
TW4-14 and TW4-27 delayed responses at these locations to such an extent that they responded
to past seepage more slowly than many nearby wells. Water levels at these wells remained lower

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than in surrounding higher permeability materials even though water levels in surrounding
materials were generally decreasing due to reduced wildlife pond seepage and pumping. Before
stabilizing in 2018, water levels at TW4-14 and TW4-27 increased. Compared to TW4-27, the
rate of increase was higher at TW4-14 due to factors that include: closer proximity to the
northern pond seepage source; a smaller thickness of low permeability materials separating
TW4-14 from surrounding higher permeability materials; and hydraulic gradients between TW4-
14 and surrounding higher permeability materials that on average were larger. Slowing of the
rates of water level increase at TW4-14 (between 2015 and 2018) and TW4-27 (between early
2014 and 2018) is attributable to reduced hydraulic gradients as TW4-14 and TW4-27 water
levels ‘caught up’ with water levels in surrounding higher permeability materials.
In addition, water levels in this area have been affected by reduced recharge at the southern
wildlife pond and the consequent decay of the associated groundwater mound. The decay of the
southern mound likely contributed to the reduction in hydraulic gradients between the low
permeability materials penetrated by TW4-14 and TW4-27 and the surrounding higher
permeability materials. TW4-27 is closer to the southern wildlife pond than TW4-14. Any
reduction in hydraulic gradients attributable to the southern pond was expected to impact TW4-
27 sooner and to a greater extent than TW4-14, consistent with the lower rate of increase in
water levels at TW4-27, and the earlier reduction in the rate of increase (since early 2014) as
discussed above.
The low permeability at TW4-14 and TW4-27 has retarded the transport of chloroform to these
wells (compared to nearby wells). TW4-14 and TW4-27 remain outside the plume; and
concentrations at these wells have remained below 10 µg/L. During the fourth quarter of 2021,
chloroform was not detected at TW4-14 and was detected at TW4-27 at approximately 4 µg/L.
Chloroform exceeding 70 µg/L at TW4-29 and formerly at TW4-33 indicated that, in addition to
migrating south from TW4-4 to TW4-6 and TW4-26, chloroform also migrated along a relatively
narrow path to the southeast from the vicinity of TW4-4 to TW4-33 then TW4-29 and eventually
to TW4-30. Such migration was in a direction nearly cross-gradient with respect to the direction
of groundwater flow implied by the historic groundwater elevations in this area, which, until
relatively recently, placed TW4-14 almost directly downgradient of TW4-4. Such migration was
historically possible because the water levels at TW4-29 have been lower than the water levels at
TW4-4 (and TW4-6); and, prior to the second quarter of 2021, the water levels at TW4-30 were
lower than the water levels at TW4-29. The permeability and historic water level distributions
are generally consistent with the apparent nearly cross-gradient migration of chloroform from
TW4-4 around the low permeability zone defined by TW4-36, TW4-14, and TW4-27.

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During the fourth quarter of 2021 chloroform at TW4-30 (located east and cross-gradient of
TW4-29) was detected at approximately 81 µg/L. TW4-30 bounded the chloroform plume to the
east until concentrations first exceeded 70 µg/L during the fourth quarter of 2020 (as discussed
above). Chloroform has not been detected at wells TW4-31 (located east of TW4-27), TW4-34
(located south and cross- to downgradient of TW4-29 and TW4-30), TW4-35 (located southeast
and generally downgradient of TW4-29 and TW4-30), nor at TW4-43 (located cross-to
downgradient of TW4-29 and TW4-30).
Data from wells within and adjacent to the southern portion of the chloroform plume indicate
that:
1. Chloroform exceeding 70 µg/L at TW4-29 is bounded by concentrations below 70 µg/L at
wells TW4-6, TW4-23, TW4-27, TW4-33, TW4-34, TW4-35 and TW4-42; however, as
discussed above, TW4-30 no longer bounds the plume immediately to the east. Although
previously downgradient of TW4-29, due to long-term changes in water levels, TW4-30
is now generally cross-gradient of TW4-29. TW4-6, TW4-23, TW4-27 and TW4-33 are
generally cross- to upgradient of TW4-29; TW4-34 and TW4-35 are generally
downgradient of TW4-29; TW4-42 is generally cross- to downgradient of TW4-29; and
TW4-43 (which bounds the plume to the east) is generally cross- to downgradient of
TW4-30.
2. Chloroform concentrations at TW4-33 that are lower than concentrations at TW4-29, and
the likelihood that a pathway exists from TW4-4 to TW4-33 to TW4-29, suggest that
concentrations in the vicinity of TW4-33 were likely higher prior to initiation of TW4-4
pumping, and that lower concentrations currently detected at TW4-33 are due to its closer
proximity to TW4-4.
3. Chloroform concentrations at TW4-26 exceeded 70 µg/L for the first time during the
second quarter of 2017. Chloroform at TW4-26 is bounded by concentrations below 70
µg/L at TW4-6 and TW4-23 (located up- to cross-gradient of TW4-26); and at TW4-34
(located generally cross- gradient of TW4-26). Chloroform has not been detected at either
TW4-23 or TW4-34. Although chloroform exceeding 70 µg/L was detected at well TW4-
40, installed approximately 200 feet south of TW4-26 in February, 2018, chloroform has
not been detected at TW4-42, installed approximately 200 feet south of TW4-40 in April,
2019. TW4-42 is generally downgradient of both TW4-26 and TW4-40 and bounds the
chloroform plume to the south.

Eventually, TW4-4 pumping, enhanced by operation of adjacent pumping well TW4-41, was
expected to reduce chloroform at both TW4-29 and TW4-33 by cutting off the source. The
decrease at TW4-33 was expected to be faster than at TW4-29 because TW4-33 is in closer
proximity to TW4-4 pumping. Such behavior was expected by analogy with the temporary
decreases in chloroform concentrations that occurred at TW4-6 and TW4-26 once TW4-4

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pumping began (discussed in Section 4.2.3). Since installation in 2013, however, concentrations
at TW4-33 appear to be relatively stable to decreasing (and have generally been decreasing since
2018). From the third quarter of 2014 until the second quarter of 2020, concentrations at TW4-29
generally increased; however since the second quarter of 2020 concentrations appear to be
relatively stable.
Chloroform trends at TW4-29 and TW4-33 suggest that chloroform migration has been arrested
at TW4-33 by TW4-4 (and TW4-41) pumping and that increased chloroform at TW4-29 resulted
from a remnant of the plume that migrated past TW4-33 and generally toward TW4-30 (which
was previously downgradient of TW4-29, and until the fourth quarter of 2020, bounded the
plume to the east). The influence of TW4-4 pumping at the distal end of the plume is consistent
with generally decreasing water levels at both TW4-29 and TW4-33. Pumping at TW4-41 since
the second quarter of 2018 is expected to help maintain or enhance this decline.
Decreasing water level trends at TW4-29 and TW4-33 are also consistent with reduced wildlife
pond seepage. The decay of the groundwater mound associated with the southern wildlife pond,
which is 3 to 4 times closer to the southern extremity of the chloroform plume than the northern
ponds, is expected to impact water levels within and adjacent to this portion of the plume.
Reduced wildlife pond seepage, in particular, reduced seepage from the southern wildlife pond,
likely contributes to decreasing water level trends at both wells (since about the fourth quarter of
2013); temporarily increased concentrations at TW4-6 subsequent to the first quarter of 2014;
and increased concentrations at TW4-26 since the third quarter of 2016.
As the groundwater mound associated with the southern pond decays, groundwater flow
directions in the southern extremity of the plume have become more southerly (rather than
southeasterly), and plume migration has turned more to the south. An increasingly southerly
direction of plume migration is consistent with increasing concentrations at TW4-26. Continued
decay of the southern mound is expected to result in eventual restoration of the typical site
southwesterly flow pattern within this portion of the plume.
Detectable chloroform concentrations at TW4-14 (between the fourth quarter of 2014 and the
first quarter of 2021) and TW4-27 (since the third quarter of 2015) suggest ongoing, but slow,
downgradient migration of chloroform from the distal end of the plume into the low
permeability materials penetrated by TW4-14 and TW4-27.
Although chloroform at the southeastern extremity of the plume may temporarily continue to
migrate to the southeast, the southeastern extremity of the plume is approximately 1,200 feet
from the closest (eastern) property boundary (Figure 1B). Site water level data suggest that the

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plume is unlikely to reach the eastern property boundary as perched water flow along the
boundary to the east of the southeastern extremity of the plume appears to be generally south-
southwesterly and sub-parallel to the boundary (Figure 1B; Figure 21; HGC, 2018d). The
southern property boundary on the east side of the site is more than three miles to the south of
the plume and the nearest downgradient discharge point (Ruin Spring) is nearly two miles to the
south-southwest of the plume. Because of the large distance to the southern property boundary,
chloroform mass removal by pumping, and natural attenuation of chloroform, it is unlikely that
chloroform within the southern or southeastern extremities of the plume will ever reach the
southern property boundary at concentrations exceeding the GCAL.
As discussed in HGC (2022), reduced dilution from reduced wildlife pond recharge caused
average chloroform concentrations and calculated residual masses within the plume to increase
after 2012; however both average concentrations and calculated residual masses have been
trending downward since 2015. In addition, the more than doubling of the number of chloroform
pumping wells since 2014 has increased mass removal rates and has helped to maintain a
relatively large proportion of the plume mass under hydraulic capture (between 89% and 99%).
Furthermore, as will be discussed in Section 4.4.3, first-order chloroform biodegradation rate
calculations presented in HGC (2007b) and HGC (2022) indicate that less than 200 years would
be required to remediate the plume, even in the absence of any direct mass removal by pumping.
3.5.4 Beneath and Downgradient of the Tailings Management System
As discussed in Section 2, more than 41 years of groundwater monitoring beneath and
downgradient of the TMS indicates that the system has not impacted groundwater. In the event
that potential seepage from the TMS should impact groundwater at a future date, the likely
pathways to known discharge points Westwater Seep and Ruin Spring are calculated in Section
3.5.4.1. Perched zone water balances within the areas near DR-2 (abandoned) and DR-5, and
flow within the vicinities of Westwater Seep and Ruin Spring are calculated in Sections 3.5.4.2
and 3.5.4.3.
3.5.4.1 Overview
Figure 25 is a perched water level contour map showing inferred pathlines from various locations
on the west or south (downgradient) dikes of TMS cells toward known discharge points
Westwater Seep and Ruin Spring. These pathlines show the primary expected directions of
perched water flow. As indicated, perched water passing beneath the west dike of cell 4B has the
potential to travel to either of known discharge points Westwater Seep or to Ruin Spring because
of an apparent groundwater divide in the vicinity of DR-2 (abandoned; Figure 1A) and DR-5.

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Perched water north of this apparent divide is expected to flow primarily northeast to Westwater
Seep and perched water south of this apparent divide is expected to flow primarily south toward
Ruin Spring. The presence of this apparent divide is consistent with enhanced recharge over this
portion of the mesa.
The path to Ruin Spring from the area south of the apparent groundwater divide is sub-parallel to
the western rim of the mesa. The path is generally along a paleovalley between the mesa rim and
the dry portion of the Brushy Basin Member paleoridge defined by MW-21 and abandoned
boring DR-18. Perched water passing beneath the south dike of cell 4B (and cell 4A) is expected
to travel south-southwest to Ruin Spring, to the east of the dry paleoridge defined by MW-21 and
abandoned boring DR-18.
As discussed previously, the data suggest that perched water flow in the southwest portion of the
site is influenced by paleotopography to a greater extent than in other areas of the site due to the
prevalence of relatively small saturated thicknesses.
As discussed in Section 2.1.4, there is no evidence to hydraulically connect Cottonwood Seep to
the perched water system; therefore no inferred flow pathway depicted in Figure 25 leads to
Cottonwood Seep. Section 3.6.3 posits a potential pathway that may hypothetically exist between
the perched zone near DR-8 and Cottonwood Seep for purposes of travel time calculations, and
to allow for the possibility that an as yet unidentified pathway may exist.
3.5.4.2 Water Balance Near DR-2 and DR-5
Enhanced recharge south/southwest of Westwater Seep near DR-2 (abandoned; Figure 1A) and
DR-5 is likely needed to maintain the relatively large saturated thicknesses there, considering the
slow rate of perched water flow into this area via the zone of small saturated thickness and the
presence of known discharge point Westwater Seep to the northeast and the paleovalley leading
south to Ruin Spring (acting as a sink).
Because the water columns in most piezometers penetrating the area of low saturated thicknesses
were inadequate for hydraulic testing, only one estimate of hydraulic conductivity was obtained,
at DR-10. As shown in Table 1, the KGS method hydraulic conductivity estimates at DR-10
(located within the area of low saturated thickness) were one to two orders of magnitude lower
than at DR-5 and DR-9, located west of the area of low saturated thickness. Assuming the
estimate at DR-10 is representative of the area of low saturated thickness, the transmissivity (the
product of hydraulic conductivity and saturated thickness) of the area of low saturated thickness
is two to three orders of magnitude lower than for the area of larger saturated thickness to the

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west (near DR-2 [abandoned], DR-5, and DR-9). Figures 5 and 25 show that the hydraulic
gradient in this area is relatively flat; the gradient does not change significantly across the area of
low saturated thickness, but flattens to the west (downgradient) of the area.
Water flows westward from the area of the TMS through the area of low saturated thickness
between DR-6 and DR-10 (Figure 25). The fourth quarter, 2021 saturated thicknesses at DR-6
and DR-10 are approximately 2 feet and 2.8 feet, respectively, averaging approximately 2.4 feet.
Using Darcy’s Law, and assuming a hydraulic conductivity of 3 x 10-6 cm/s (0.0084 feet per day
[ft/day], based on the KGS estimate provided for DR-10 in Table 1), an average hydraulic
gradient of approximately 0.0058 ft/ft, an average saturated thickness of approximately 2.4 ft,
and a width of approximately 1,600 feet (the approximate distance between DR-6 and DR-10),
the rate of perched water flow westward through the area of low saturated thickness is
approximately 0.187 cubic feet per day (ft3/day) or 0.00097 gpm.
Water flows out of the area of larger saturated thickness (near DR-2 [abandoned] and DR-5) to
the northeast toward known discharge point Westwater Seep and to the south through the
paleovalley leading towards known discharge point Ruin Spring. The rate of flow out of this area
northeast to Westwater Seep is expected to be smaller than the discharge rate at Westwater Seep
which also receives water from the east and northeast. The discharge rate at Westwater Seep is
too small for a reliable estimate. However, the rate of flow south through the paleovalley leading
towards Ruin Spring can be calculated using the geometric average hydraulic conductivity of
0.0089 ft/day (based on KGS estimates for DR-8 [October, 2012 estimate], DR-9, and DR-10 in
Table 1), an approximate hydraulic gradient of 0.0080 ft/ft (between DR-9 and DR-14), an
average saturated thickness of approximately 12 ft, and a width of approximately 2,250 ft
(between DR-8 and DR-10), as 1.9 ft3/day, or approximately 0.01 gpm, an order of magnitude
larger than the calculated flow into the area. The difference between calculated inflow and
outflow is approximately 0.009 gpm.
These calculations indicate that an additional water source is needed to maintain the relatively
large saturated thicknesses west of the area of low saturated thickness between DR-6 and DR-10;
otherwise Westwater Seep and the paleovalley to the south would drain the area of larger
saturated thickness more quickly than water was supplied. The most likely source of additional
water is infiltration of precipitation enhanced by the direct exposure of weathered Dakota
Sandstone and Burro Canyon Formation, and the thinness or absence of any overlying low
permeability materials such as the Mancos Shale. Assuming uniform recharge over the portion of
the mesa west of Westwater Seep and north of DR-8 and DR-9 (an area of approximately 175
acres, or 7.6 x 106 square feet [ft2]), the calculated difference of 0.009 gpm implies a
conservatively low recharge rate of approximately 0.001 inches per year (in/yr). Most of the

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recharge likely occurs near the mesa rim where the Dakota Sandstone and Burro Canyon
Formation are exposed (Figure E.1 and Figure E.2, Appendix E). Such recharge is expected to be
enhanced within drainages where they cross weathered Dakota Sandstone and Burro Canyon
Formation.
Furthermore, these calculations indicate that perched water flow in the portion of the site south
of Westwater Seep is inadequate as a primary supply to Cottonwood Seep. Perched water flow
from the area of the TMS through the area of low saturated thickness towards Cottonwood Seep
would have to be more than three orders of magnitude higher than calculated above to provide a
supply of between approximately 1 and 10 gpm. The required flow would have to be even larger
considering that some of the incoming flow is diverted to known discharge point Westwater Seep
and to the paleovalley that leads south to known discharge point Ruin Spring. Even if this
calculation were performed using the geometric average of the KGS hydraulic conductivity
estimates for all tested DR-series piezometers (approximately 1 x 10-5 cm/s or 0.028 ft/day)
rather than the estimate for DR-10 (3 x 10-6 cm/s or 0.0084 ft/day), the calculated rate of flow
through the area of low saturated thickness would be approximately 0.0032 gpm, which is still
approximately three orders of magnitude lower than the estimated discharge rate of Cottonwood
Seep. The inadequacy of the perched zone as the primary supply to Cottonwood Seep indicates
that the primary source or sources of Cottonwood Seep lie elsewhere.
3.5.4.3 Water Balance Near Ruin Spring and Westwater Seep
Figure 26 is a map showing inferred perched groundwater pathlines in the immediate vicinities
of Ruin Spring and Westwater Seep. These pathlines were used to estimate expected flow rates
to these features based on Darcy’s Law using local hydraulic gradients, saturated thicknesses,
and hydraulic conductivity estimates. Saturated thicknesses posted on Figure 26 were calculated
as the difference between kriged fourth quarter, 2021 water level and top of Brushy Basin
Member surfaces.
The water level contours plotted on Figure 26 do not demonstrate the increase in hydraulic
gradient that would generally be expected when groundwater approaches a discharge point such
as Ruin spring (or an extraction well). However, the increase in hydraulic gradient is evident if
an additional data point, DR-25 (Figure 1A), is considered. Boring DR-25 was abandoned during
2011; however, as shown in Figure 20, water levels at DR-series piezometers have been stable.
Therefore, the water level at abandoned boring DR-25 at the present time would likely be about
the same as the second quarter, 2011 water level that was included in Figure 19. As shown in
Figure 19 the water table (and hydraulic gradient) show the expected steepening approaching
Ruin Spring.

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The area of the perched zone providing flow to Ruin Spring was estimated by assuming the flow
is approximately divided between Ruin Spring to the west and Corral Springs to the east. This
division coincides approximately with a groundwater divide that extends southwest from the
southern wildlife pond toward Ruin Spring, approximately parallel to the southeasternmost flow
path depicted on Figure 21. Using the geometric average hydraulic conductivity based on
estimates at DR-21, DR-23, and DR-24 (2.2 x 10-5 cm/s or 0.062 ft/day based on KGS analysis
of automatically logged slug test data [Table 6]), which are closest to Ruin Spring, an average
hydraulic gradient of approximately 0.011 ft/ft, and an average saturated thickness of
approximately 15.5 feet over a width of approximately 8,400 feet (along the 5420 foot elevation
contour), yields a rate of perched flow of approximately 80 ft3/day or 0.42 gpm.
The calculated value of 0.42 gpm is slightly less than the estimated average flow for Ruin Spring
of approximately 0.5 gpm. Assuming that the difference between the calculated perched water
flow and the estimated flow at Ruin Spring (0.08 gpm or approximately 15 ft3/day) is due to
local recharge over the area of Figure 26 covered by the inferred flow paths (approximately 420
acres or 18.3 x 106 ft2), then the local recharge rate needed to make up the difference is
approximately 8.2 x 10-7 ft/day or 0.0036 in/yr. If the average flow for Ruin Spring were as high
as 1 gpm, then approximately 0.58 gpm, or 0.027 in/yr of local recharge would be needed to
make up the difference. Both estimates of local recharge are relatively small and within a range
that is reasonable considering the topography and surface lithology of this portion of the site.
Perched groundwater flow to Westwater Seep was similarly estimated. Hydraulic conductivities
used in the calculations are summarized in Table 6. Hydraulic conductivity estimates at DR-5,
DR-8, DR-9, DR-10, and DR-11 are based on automatically logged slug test data analyzed using
the KGS solution method; estimates at MW-12, MW-14, and MW-15 are based on pumping test
analyses reported in TITAN (1994) [Table 4]. Estimates from DR-2, DR-16, and DR-17 are not
available as hydraulic tests could not be performed because these borings were abandoned after
surveying and water level collection based on the criteria presented in HGC (2012b). Tests also
could not be performed at DR-6 nor DR-7 due to an insufficient water column.
Using a geometric average hydraulic conductivity of 9.8 x 10-6 cm/s (0.027 ft/day), an average
hydraulic gradient of 0.013 ft/ft, and an average saturated thickness of 5 feet over a width of
approximately 3,300 feet, yields a rate of perched flow of approximately 5.8 ft3/day or 0.03 gpm.
If the geometric average of the hydraulic conductivities estimated at the four closest wells (MW-
23, MW-24, MW-35, and DR-5) is substituted (1.8 x 10-5 cm/s [0.05 ft/day]), the calculated rate
of perched flow is 10.7 ft3/day or 0.056 gpm. In calculating the latter average, the highest
estimate from the MW-24 test was used. Because the flow to Westwater Seep is too small to be
reliably measured (as discussed in Section 3.7), either result is considered reasonable.

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3.6 Perched Water Migration Rates and Travel Times
Perched groundwater pore velocities and travel times along selected pathlines shown in Figure
27 were calculated using Darcy’s Law. The calculated pore velocities and travel times are
representative of the movement of a conservative solute assuming no hydrodynamic dispersion.
Hydraulic conductivity estimates used for pathlines 1, 2A, and 2B are summarized in Table 7,
and for pathlines 3 through 6 in Table 8. Pore velocity estimates are summarized in Table 9.
3.6.1 Nitrate Investigation Area
Perched groundwater pore velocities and travel times were calculated along Path 1 (Figure 27)
located within the nitrate plume. Path 1 is approximately 1,940 feet long. Under current
conditions, a particle migrating along Path 1 would be captured by nitrate pumping well TW4-24
(near the center of the plume).
The average hydraulic conductivity along Path 1 is assumed to be the geometric average of the
conductivities of wells located within and immediately upgradient and downgradient of the
nitrate plume (wells TWN-2, TWN-3, TWN-18, TW4-21, TW4-22, TW4-24, TW4-25, TW4-37,
MW-11, MW-27, MW-30, and MW-31) as estimated by analyzing automatically logged slug test
data using the KGS solution (Table 7). Using a geometric average conductivity of 1.19 x 10-4
cm/s (0.33 ft/day), a hydraulic gradient of 0.0165 ft/ft, and a porosity of 0.18, the estimated
average pore velocity along Path 1 is approximately 11 ft/yr. This implies that, under current
conditions, approximately 176 years would be required to traverse Path 1.
Historic hydraulic gradients within the area of the nitrate plume were likely substantially larger
than 0.0165 ft/ft during the time prior to Mill construction when the historical pond was active
(Figure 1B). The depth to water at TWN-2, located within the former footprint of the historical
pond (Figure 1B), was approximately 16 feet bls prior to its conversion to a nitrate pumping
well. The relatively small depth to water is interpreted to result from the relatively low perched
zone permeability at TWN-2 (approximately 1.5 x 10-5 cm/s) and slightly elevated recharge by
precipitation resulting from the relatively flat topography in that portion of the site. When the
historical pond was active and ponded water was present in the vicinity of TWN-2, depths to
water were likely negligible as the associated groundwater mound likely reached an elevation
just beneath the pond bottom.
Historic water level maps (Appendix D) show that water levels in the vicinities of MW-30 and
MW-31, located along the downgradient margin of cell 2, and at the downgradient margin of the
nitrate plume, were approximately 5,520 feet amsl. Assuming that the perched water level
beneath the historical pond was close to the pond bottom (approximately 5,625 feet amsl), the

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perched water level at the downgradient edge of cell 2 was approximately 5,520 feet amsl, and
the distance between the southern edge of the historical pond and the downgradient edge of cell 2
was approximately 2,200 feet, the historic hydraulic gradient is calculated as approximately
0.048 ft/ft. This estimate is more than four times the overall average site hydraulic gradient of
approximately 0.011 ft/ft (calculated between TWN-19 and Ruin Spring).
Using the geometric average hydraulic conductivity of 0.33 ft/day (as discussed above), the
estimated historic hydraulic gradient of 0.048 ft/ft, and a porosity of 0.18, the estimated historic
pore velocity downgradient of the historical pond is approximately 32 ft/yr, implying that nitrate
originating from the historical pond could have migrated to the downgradient edge of cell 2
within 69 years. Assuming the historical pond was active circa 1920, that nitrate was
conservative, and ignoring hydrodynamic dispersion, nitrate originating from the historical pond
could have reached the vicinities of MW-30 and MW-31 by 1989.
3.6.2 Vicinity of Chloroform Plume
Perched groundwater pore velocities and travel times along Paths 2A and 2B (Figure 27), located
within the vicinity of the chloroform plume, were calculated. Path 2A is approximately 1,045
feet long and path 2B is approximately 1,080 feet long. Under current conditions, a particle
migrating along Path 2A would be captured by chloroform pumping well MW-26, and. a particle
migrating along Path 2B would be captured by chloroform pumping well TW4-2. In evaluating
average hydraulic conductivities along these paths, estimates assuming both confined and
unconfined conditions were used. This methodology is considered appropriate for this area of the
site because of the potential for semi-confined conditions to exist at least locally (HGC, 2004).
The average hydraulic conductivity along Path 2A is assumed to be the geometric average of the
conductivities of nearby wells MW-26, TW4-5, TW4-9, TW4-10, TW4-18 and TW4-39 (Table
7). Using a geometric average conductivity of 3.23 x 10-4 cm/s (0.9 ft/day), a hydraulic gradient
of 0.0344 ft/ft, and a porosity of 0.18, the estimated average pore velocity along Path 2A is
approximately 63 ft/yr. This pore velocity implies that, under current conditions, approximately
17 years would be required to traverse Path 2A.
The average hydraulic conductivity along Path 2B is assumed to be the geometric average of the
conductivities of nearby wells MW-4A, TW4-2, TW4-8, TW4-9, TW4-28, TW4-32 and TW4-38
(Table 7). Estimates based on the early time data for MW-4A (formerly located approximately
10 feet south of MW-4) were used in calculating the averages because these data are considered
more representative of conditions in the immediate vicinity of MW-4. Using a geometric average
conductivity of 1.18 x 10-4 cm/s (0.33 ft/day), a hydraulic gradient of 0.057 ft/ft, and a porosity

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of 0.18, the estimated average pore velocity along Path 2B is approximately 38 ft/yr. This pore
velocity implies that, under current conditions, approximately 28 years would be required to
traverse Path 2B.
Historic hydraulic gradients within the northern (upgradient) areas of the eastern portion of the
chloroform plume (prior to about 1990) were likely larger and contributed to relatively rapid
movement of chloroform from the abandoned scale house leach field (located immediately north
of TW4-18) to MW-4 where chloroform was detected in 1999. The assumptions are made that 1)
water levels near the abandoned scale house leach field were affected relatively early by wildlife
and/or historical pond seepage (owing to the close proximity of the northern wildlife ponds and
historical pond); and 2) that the water level at TW4-18, which was relatively stable and averaged
approximately 5,586 ft amsl between installation in 2002 and cessation of water delivery to the
northern wildlife ponds in 2012, is representative of the water level at the leach field circa 1980.
Based on these assumptions and the historic water level maps provided in Appendix D, the
hydraulic gradient over the approximate 1,200 foot distance between the abandoned scale house
leach field and MW-4 was approximately 0.048 ft/ft in 1990 and approximately 0.029 ft/ft in
1999, averaging 0.038 ft/ft. This is more than three times the overall average site hydraulic
gradient of approximately 0.011 ft/ft (calculated between TWN-19 and Ruin Spring) but is
within the range of hydraulic gradients occurring at present within and adjacent to the
chloroform plume, and is similar to the current hydraulic gradient of approximately 0.041 ft/ft
just east the plume, between non-pumping wells TW4-36 and TW4-27.
Using a geometric average hydraulic conductivity of 1.1 ft/day based on Table 3 estimates from
wells MW-4A, TW4-5, TW4-9, TW4-10, and TW4-18 (located near a line connecting MW-4
with the abandoned scale house leach field), an estimated historic hydraulic gradient of 0.038
ft/ft, and a porosity of 0.18, the calculated average pore velocity prior to 1999 was approximately
84 ft/yr. This is sufficient for chloroform to have migrated from the abandoned scale house leach
field to MW-4 between 1978 and 1999. This calculation implies that chloroform could have
migrated nearly to TW4-4 by 1999.
3.6.3 Beneath and Downgradient of Tailings Management System
Estimated times for a hypothetical conservative solute originating from the TMS to migrate
downgradient to known discharge points Westwater Seep and Ruin Spring assuming no
dispersion are calculated in the following Sections. Because the hypothetical conservative solute
is assumed to originate from individual cells within the system, the time for the solute to migrate
downward from the base of a cell to the perched water must be taken into account. Vadose zone
travel times are estimated in Section 3.6.3.1. Total travel times are estimated in Section 3.6.3.2.

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3.6.3.1 Vadose Zone
Depths to perched groundwater near cell 2 vary from approximately 66 feet btoc near the
northeast (upgradient) corner of the cell to approximately 110 feet btoc at the northwest corner of
the cell. Depths to water near cell 3 vary from approximately 69 feet btoc near the northeast
(upgradient) corner of the cell to approximately 114 feet btoc at the southwest (downgradient)
corner of the cell. Depths to water near cells 4A and 4B vary from approximately 81 feet btoc
near the northeast (upgradient) corner of cell 4A to approximately 114 feet btoc along the
western margin of cell 4B. The average depth to water near cell 2 is approximately 80 feet btoc;
near cell 3 approximately 92 feet btoc; and near cells 4A and 4B approximately 104 feet btoc.
Because the cells are installed a maximum of approximately 25 feet below grade, the average
depth to perched water from the base of cell 2 is approximately 55 feet; beneath cell 3
approximately 67 feet; and beneath cells 4A and 4B approximately 79 feet.
Any seepage through the cell liners would have to travel downward through approximately 55
feet of vadose materials to impact perched water beneath cell 2; through approximately 67 feet to
impact perched water beneath cell 3; and through approximately 79 feet to impact perched water
beneath cells 4A and 4B.
Knight-Piésold (1998) estimated a maximum volumetric seepage rate for cell 3 based on cell
construction and liner characteristics, of approximately 80 cubic feet per day (ft/day) or 0.42
gpm over the entire cell. Most of this seepage was estimated to be via diffusion through the liner.
This rate was estimated to decrease over time as the cell desaturates once the final cover is
emplaced. Assuming a cell footprint of 3.38 x 106 ft2, this maximum rate is equivalent to 2.37 x
10-5 ft/day or 0.0086 ft/yr.
The average saturation expected in vadose bedrock beneath the TMS is approximately 20%
based on saturations measured in bedrock samples presented in Table 5 (from TITAN, 1994).
Assuming that the Knight-Piésold estimates from cell 3 are also representative of cell 2 and cells
4A and 4B, and assuming that this rate of seepage would not significantly raise the average
saturation of the underlying vadose zone materials, the average rate of downward movement of a
conservative solute dissolved in the seepage, assuming 1) no hydrodynamic dispersion, 2) an
average water saturation of 0.20, and 3) an average porosity of 0.18, can be approximated as:
yrftyrft/24.0)18(.)20(.
/0086.0 =

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The average times to travel from cell liners to the perched water zone would then be
approximately 229 years beneath cell 2; 279 years beneath cell 3; and 329 years beneath cells 4A
and 4B. These are conservative estimates because the maximum estimated seepage rate is used,
and the average vadose zone water saturations would be likely to increase (because some of the
seepage would go into storage), thereby reducing the downward rates of travel, and increasing
the travel times.
Numerical modeling of potential TMS seepage and rates of downward migration of solutes are
provided in MWH (2010). Based on Figure A-3 from MWH (2010), the simulated seepage rates
beneath cells 2 and 3 would reach a maximum of approximately 7.7 millimeters per year
(mm/yr) [0.025 ft/yr] by year 25, then drop to approximately 0.7 mm/yr (0.0023 ft/yr) by year
70. The average seepage rate over the 240 year simulation period is approximately 0.0043 ft/yr,
half the estimate used in the above calculations. Using this rate with the above assumptions
would double the travel times estimated for seepage to reach perched water beneath cells 2, 3,
and 4A and 4B. However, the MWH analyses used smaller initial water saturations for the
vadose zone which correspondingly reduced travel time estimates. Based on personal
communication with MWH personnel, a 200+ year vadose zone travel time estimate for cells 2
and 3 is considered reasonable.
The estimates calculated above for cell 2 (229 years), cell 3 (279 years) and cells 4A and 4B
(329 years) will be used in subsequent calculations. Because cells 2 and 3 are at least 38 years
old, the travel times starting from the present time will be 191 years for cell 2, and 241 years for
cell 3. Cell 4B was installed in 2010 and cell 4A refurbished and put into use shortly thereafter
so the effective travel time will be assumed to be 317 years for these cells. Furthermore, the
estimates for cells 4A and 4B are considered even more conservative because of improvements
in cell design and liner quality that were incorporated in these cells but were not available during
construction of cells 2 and 3.
3.6.3.2 Perched Water Zone Downgradient of Tailings Management System
Perched groundwater pore velocities and travel times along selected paths between the existing
TMS and perched water discharge points were calculated for pathlines 3 through 6 shown in
Figure 27.
The Figure 27 pathlines were selected as the shortest Figure 25 paths from the TMS to a)
Westwater Seep (Path 3), b) Ruin Spring via the west side of the Brushy Basin paleoridge (Path
5), and c) Ruin Spring via the east side of the Brushy Basin paleoridge (Path 6). A pathline from
the TMS to the vicinity of DR-8 (Path 4) is also shown on Figure 27. From the vicinity of DR-8

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perched water is expected to flow primarily south (within a paleovalley) toward Ruin Spring.
However, a potential pathline from the vicinity of DR-8 is also shown in Figure 27 that posits a
hypothetical connection between the perched zone and Cottonwood Seep. Path 4 provides the
shortest pathline between the TMS and the western edge of the perched zone near DR-8, and the
potential path provides the shortest hypothetical connection between the western edge of Path 4
and Cottonwood Seep.
Hydraulic conductivities used in the calculations are summarized in Table 8. Hydraulic
conductivity estimates are based on automatically logged slug test data analyzed using the KGS
solution method, except for MW-12, MW-14, and MW-15. Hydraulic conductivity estimates at
MW-12, MW-14, and MW-15 are based on pumping test analyses reported in Table 4 (from
TITAN, 1994). Hydraulic tests could not be performed at DR-2, DR-16, DR-18, nor DR-25.
These borings were abandoned after surveying and water level collection based on the criteria
presented in HGC (2012b). Tests also could not be performed at DR-6 nor DR-7 due to
insufficient water column height. Pore velocity calculations for pathlines 3 through 6 are
summarized in Table 9.
Path 3 is approximately 2,200 feet long with an average hydraulic gradient of 0.0136 feet per
foot (ft/ft) based on the fourth quarter, 2021 water level at MW-23 (5,498 ft amsl) and the
elevation of Westwater Seep (5,468 ft amsl). The geometric average hydraulic conductivity of
the perched zone in the vicinity of Path 3 (based on data from DR-5, DR-8, DR-9, DR-10, DR-
11, MW-12, MW-23, MW-24, and MW-36) is 9.8 x 10-6 cm/s (0.027 ft/day or 10 ft/yr).
Assuming an effective porosity of 0.18, the average perched water pore velocity along Path 3 is
0.76 feet per year (ft/yr), yielding a travel time of approximately 2,895 years. Including a vadose
zone travel time of approximately 279 years for cell 3, the total travel time is approximately
3,175 years.
Path 4 is approximately 4,125 feet long with an average hydraulic gradient of 0.0046 ft/ft based
on the fourth quarter, 2021 water level at MW-36 (5,493 ft amsl) and the water level at DR-8
(5,474 ft amsl). The geometric average hydraulic conductivity of the perched zone in the vicinity
of Path 4 (based on data from DR-5, DR-8, DR-9, DR-10, DR-11, MW-12, MW-23, MW-24,
and MW-36) is 9.8 x 10-6 cm/s (0.027 ft/day or 10 ft/yr). Assuming an effective porosity of 0.18,
the average perched water pore velocity along Path 4 is 0.26 feet per year (ft/yr), yielding a
travel time of approximately 15,865 years. Including a vadose zone travel time of approximately
329 years for cell 4A, the total travel time is approximately 16,195 years. The additional time to
travel along the hypothetical pathway to Cottonwood Seep is not calculated because of the
hypothetical nature of the pathway and because the hypothetical pathway is through the Brushy
Basin Member which is considered an aquiclude. If such a pathway exists, the combined travel

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time along Path 4 and the hypothetical pathway (which adds approximately 2,150 horizontal feet
to the total path length), would be significantly greater than 16,195 years.
Path 5 is approximately 11,800 feet long with an average hydraulic gradient of 0.0096 ft/ft based
on the fourth quarter, 2021 water level at MW-36 (5,493 ft amsl) and the elevation of Ruin
Spring (5,380 ft amsl). The geometric average hydraulic conductivity of the perched zone in the
vicinity of Path 5 (based on test data from DR-5, DR-8, DR-9, DR-10, DR-11, DR-14, DR-17,
DR-19, DR-20, DR-21, DR-23, DR-24, MW-23, MW-24, and MW-36) is 1.1 x 10-5 cm/s (0.031
ft/day or 11.3 ft/yr). Assuming an effective porosity of 0.18, the average perched water pore
velocity along Path 5 is 0.60 ft/yr, yielding a travel time of approximately 19,665 years.
Including a vadose zone travel time of approximately 329 years for cell 4A, the total travel time
is approximately 19,995 years.
Path 6 is approximately 9,700 feet long with an average hydraulic gradient of 0.0116 ft/ft based
on the fourth quarter, 2021 water level at MW-37 of 5,493 ft amsl and the elevation of Ruin
Spring (5,380 ft amsl). The geometric average hydraulic conductivity of the perched zone in the
vicinity of Path 6 (based on test data from DR-11, DR-13, DR-21, DR-23, MW-3, MW-14, MW-
15, MW-20 and MW-37) is 1.38 x 10-5 cm/s (0.039 ft/day or 14.1 ft/yr). Assuming an effective
porosity of 0.18, the average perched water pore velocity along Path 6 is 0.91 ft/yr, yielding a
travel time of approximately 10,660 years. Including a vadose zone travel time of approximately
329 years for cell 4B, the total travel time is approximately 10,990 years.
3.7 Implications for Seeps and Springs
The lithologic and hydraulic data collected from the southwest area investigation (HGC 2012b)
allow a more comprehensive assessment of the hydrogeology of the site and have implications
with regard to seeps and springs southwest of the site. The data indicate that dilution of perched
water by local recharge is expected to occur in the vicinities of Westwater Seep and Ruin Spring,
and that perched zone permeabilities and flow rates in the southwestern portion of the site are too
low (by several orders of magnitude) for the perched zone to serve as the primary source of
water for Cottonwood Seep.
3.7.1 Westwater Seep and Ruin Spring
As discussed in HGC (2010g) the water source for both Westwater Seep and Ruin Spring is
lateral flow from upgradient portions of the perched zone enhanced by local recharge near the
edge of the mesa. Most of this recharge likely occurs near the mesa rim where weathered Dakota
Sandstone and Burro Canyon Formation are largely exposed. Such recharge is likely to be

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enhanced within drainages where they cross weathered Dakota Sandstone and Burro Canyon
Formation. The results of the southwest area investigation (HGC, 2012b) indicate that the
permeability of the perched zone in the southwest area of the site is on average lower than was
estimated prior to 2010 (as in HGC, 2009) and that the contribution to flow at Westwater Seep
and Ruin Spring by local recharge may be more significant than previously thought.
3.7.2 Cottonwood Seep
The low perched zone permeabilities and small saturated thicknesses in the southwest area of the
site are consistent with low rates of perched water flow, as shown by the calculated flow through
the area of small saturated thickness southwest of the TMS (between DR-6 and DR-10) provided
in Section 3.5.4.2. This low rate of perched water flow (approximately 0.00097 gpm) is
inadequate (by more than three orders of magnitude) to function as the primary supply to
Cottonwood Seep which has historic flows estimated to lie between 1 and 10 gpm. As discussed
in Section 3.5.4.2, the estimated flow of between 1 and 10 gpm at Cottonwood Seep is consistent
with Dames and Moore (1978).
In summary, the perched zone cannot be the primary source of water to Cottonwood Seep for the
following reasons:
1. Cottonwood Seep occurs in the lower third of Brushy Basin Member, approximately 230
feet below the contact between the Burro Canyon Formation and the Brushy Basin
Member, more than 1,500 ft west of the termination of the perched zone, and just west of
a change in morphology from slope-former to bench-former. The change in morphology
is indicative of a change in lithology. As discussed in HGC (2010g) Cottonwood Seep
likely originates from coarser-grained materials within the lower portion of the Brushy
Basin Member. Alternatively, Cottonwood Seep may originate from coarser-grained
materials of the Westwater Canyon (sandstone) Member intertongueing with the
overlying Brushy Basin Member at the transition between the two Members. The
presence of coarser-grained materials similar to the Salt Wash (sandstone) Member
within the lower portion of the Brushy Basin member is discussed in Shawe (2005). The
intertongueing of the Westwater Canyon and Brushy Basin Members is discussed in
Craig et al. (1955) and Flesch (1974). Based on lithologic cross sections provided in
TITAN (1994), the elevation of Cottonwood Seep (5,234 ft amsl) is within 5 to 15 feet of
the elevation of the contact between the Brushy Basin Member and the underlying
Westwater Canyon Member (5,220 to 5,230 ft amsl). This is also shown in Figure 3.
2. The historic flow at Cottonwood Seep exceeds the flow in the perched zone in the area
southwest of the TMS by several orders of magnitude. Historic flows at Cottonwood
Seep are relatively large compared to seeps and springs known to originate from the
perched zone, consistent with a primary source other than perched water.

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3. There is no evidence to establish a direct hydraulic connection between the perched zone
and Cottonwood Seep, located more than 1,500 ft west of the termination of the Burro
Canyon Formation which hosts the perched water zone. Examination of the area between
Cottonwood Seep and mesa rim (the edge of the perched zone) reveals that the upper
portion of the Brushy Basin Member appears dry and no previously undiscovered seeps
originating from the Burro Canyon Formation near Cottonwood Seep were identified.

Because the results of the southwest area investigation do not provide evidence that Cottonwood
Seep is hydraulically connected to the perched water system at the site, and because the perched
zone near Cottonwood Seep is inadequate as a primary supply, the primary source (or sources) of
water to Cottonwood Seep must lie elsewhere. The primary source(s) must be significant to
supply consistent historic flows at rates between 1 and 10 gpm. By contrast, flows at Ruin Spring
(estimated at approximately 1/2 gpm, consistent with Dames and Moore, 1978) are lower than at
Cottonwood Seep (historically between 1 and 10 gpm), and flows at Westwater Seep are too
small to measure reliably. Westwater Seep generally consists of damp soil that can be sampled
only by excavating and waiting for enough water to seep in for sample collection (see Figures 28
and 29 taken from HGC, 2010g).
Although no evidence of a direct hydraulic connection between the perched zone and
Cottonwood Seep was provided by the southwest area investigation, the possibility of a
hypothetical, as yet unknown, connection was postulated for the purpose of calculating a travel
time from the TMS to the western edge of the perched zone (near DR-8), and thence along a
potential pathway to Cottonwood Seep. The total travel time from the TMS to DR-8 was
calculated as approximately 16,195 years. Should a potential pathline such as that shown in
Figure 27 exist, the total time needed to travel from the TMS to Cottonwood Seep would be
significantly larger than 16,195 years.
3.7.3 Potential Dilution of Perched Water Resulting from Local Recharge of the Dakota
and Burro Canyon Near Seeps and Springs
As discussed in Section 3.5.4.2, the rate of flow in the perched water zone in the southwest area
of the site is small and a contribution from local recharge is needed to explain many areas of
relatively high saturated thickness near discharge points such as Westwater Seep and Ruin
Spring that are downgradient of areas of relatively low saturated thickness. The presence of local
recharge is expected to affect the water quality of seeps and springs and has the potential to
dilute any dissolved constituents that may migrate from upgradient areas.

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3.8 Implications for Transport of Chloroform and Nitrate
Chloroform and nitrate plumes are under remediation by pumping. Pumping systems are
designed to remove chloroform and nitrate mass from the perched zone as quickly as is practical
to allow natural attenuation in the far downgradient portions of the plumes to be more effective.
Furthermore, nitrate pumping is designed to capture approximately the northern 2/3 of the nitrate
plume. Pumping at the downgradient margin of the chloroform plume has generally been
impractical primarily due to low permeability and low productivity conditions. Only one
chloroform pumping well, TW4-40, is both positioned at the downgradient edge of the plume
and within materials having permeabilities large enough to support meaningful pumping and
mass removal rates. Pumping at the downgradient margin of the nitrate plume (at MW-30 and
MW-31) has also been impractical primarily because of the potential to draw chloroform
downgradient.
In the absence of remedial pumping, the western portion of the nitrate plume would eventually
migrate towards Westwater Seep and the eastern portion toward Ruin Spring (Figure 21 and
Figure 30). However, as discussed in HGC (2018e), numerical flow and transport modeling
using conservatively large hydraulic conductivities and hydraulic gradients, and conservatively
small dispersivities, demonstrates that natural attenuation, even in the absence of nitrate
reduction by pyrite and mass removal by pumping, would reduce all concentrations within the
nitrate plume to less than the 10 mg/L GCAL before reaching a property boundary.
In the absence of remedial pumping, the western portion of the chloroform plume would
eventually migrate towards Ruin Spring and the eastern portion toward the perched groundwater
low defined by TW4-35 and recently installed well TW4-43 (Figures 22 and 30). Should this low
eventually disappear, chloroform within the eastern extremity of the plume would be expected to
migrate towards the lobe of the White Mesa between Ruin and Corral Springs. In addition, the
continuing decay of the perched groundwater mound associated with the southern wildlife pond
and the resulting more southerly to southwesterly flow within the southern portion of the plume,
is expected to place Ruin Spring downgradient of the entire plume.
As indicated by calculations in Section 3.6, thousands of years would be required for either the
chloroform or nitrate plume to reach a discharge point. That is sufficient time for both
chloroform and nitrate to degrade naturally prior to reaching a discharge point as will be
discussed in Section 4.4. Furthermore, as discussed above, numerical flow and transport
modeling using conservative assumptions demonstrates that all concentrations within the nitrate
plume would be reduced to less than the 10 mg/L GCAL before reaching a property boundary,
even in the absence of mass removal by pumping and pyrite degradation.

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Groundwater lows at TW4-35 and relatively recently installed well TW4-43 are interpreted to
result from partial hydraulic isolation from upgradient and cross-gradient areas that were more
strongly affected by wildlife pond seepage. Prior to 2012, wildlife pond seepage resulted in
increases in water levels at wells in the vicinity of TW4-27 as shown in Figure 31. Prior to 2012,
water levels in wells TW4-6, TW4-26, and TW4-13 rose relatively rapidly compared with water
levels at TW4-14. The permeabilities of TW4-6 and TW4-26 are similar (Table 1) and both
exhibit similar water level behavior. The permeability at TW4-27 is relatively low (Table 1), and
the similar water level behavior at TW4-14 and TW4-27 between 2012 and 2014 suggests that
TW4-14 is also installed in low permeability materials. After 2012, water levels at TW4-27
began to stabilize; however water levels at TW4-14 continued to increase until about 2018 before
reaching relative stability. These differences in water level behavior are likely due to the relative
distances of these wells from the northern and southern wildlife ponds. That both wells are
having a delayed response to reduced wildlife pond recharge is also consistent with low
permeability at both locations.
The low permeability at TW4-27, the inferred low permeability at TW4-14, and the low
permeability at TW4-36 (Table 1) suggests that a continuous low-permeability zone extends
from TW4-27 through TW4-14 to TW4-36. These low permeability materials are the likely
cause of the partial hydraulic isolation of TW4-35 and TW4-43. Because the groundwater lows
at these wells are interpreted to result from variable permeability and from transient hydraulic
conditions brought on by former wildlife pond seepage, water levels in this area are expected to
‘catch up’ eventually with water levels in less hydraulically isolated areas.
Water balance calculations near Westwater Seep and Ruin Spring (Section 3.5.4.3) indicate that
local recharge is needed to maintain areas having relatively large saturated thicknesses that
supply water to known discharge points Westwater Seep and Ruin Spring but that are isolated
from other portions of the perched zone by areas of relatively low saturated thickness. The
presence of local recharge near these discharge points at least partly explains reported increased
flow at these features after precipitation events (HGC, 2010g). In the unlikely event that nitrate
or chloroform not removed by pumping did not degrade within the thousands of years needed to
reach a discharge point, local recharge would act to reduce concentrations prior to discharge.

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4. COMPOSITION OF DAKOTA SANDSTONE AND
BURRO CANYON FORMATION
As discussed in HGC (2012c), samples of selected archived drill core and drill cuttings were
analyzed visually and quantitatively by an analytical laboratory. Table 10 summarizes the
mineralogy of samples submitted to the contract laboratory for quantitative analysis. Table 11
summarizes the occurrence of pyrite, iron oxides, and carbonaceous material in site drilling logs
having sufficient detail. Table 12 summarizes the results of laboratory visual (microscopic)
analyses for sulfides. Table 13 and Figure 32 summarize the occurrence of pyrite in site borings
based on both lithologic logs and laboratory analyses.
4.1 Mineralogy
As discussed in Section 3.1.2, the Dakota Sandstone is a relatively hard to hard, generally fine-
to-medium grained sandstone cemented by kaolinite clays. The underlying Burro Canyon
Formation is similar to the Dakota Sandstone but is generally more poorly sorted, contains more
conglomeratic materials, and becomes argillaceous near its contact with the underlying Brushy
Basin Member of the Morrison Formation. Because of the similarity of the Burro Canyon
Formation and Dakota Sandstone they are typically not distinguished in lithologic logs at the
site.
Based on quantitative analysis of samples for major and minor mineralogy (Table 10), the
primary mineral occurring in the Burro Canyon Formation is quartz (greater than or equal to
80% in all analyzed samples except SS-26 which consisted of ‘play sand’). Other detected
minerals (not necessarily present in all the samples) include potassium feldspar, plagioclase,
mica, kaolinite, calcite, dolomite, anhydrite, gypsum, pyrite, hematite, and magnetite. Because of
their relatively high reactivity, pyrite, calcite and dolomite are expected to have the most
potential to impact perched water chemistry. The presence of carbonaceous matter (Table 11) is
also expected to impact perched water chemistry.
4.2 Pyrite Occurrence
As discussed in Section 3.1.4 pyrite occurs within the Dakota Sandstone and Burro Canyon
Formations which host the perched groundwater at the site. Table 11 summarizes the occurrence
of pyrite, iron oxides, and carbonaceous material in site lithologic logs. These logs were based on
field logging of drill cuttings and/or core samples at the time of drilling. Pyrite has been noted in
approximately 2/3 of site borings having detailed lithologic logs. These borings are located
upgradient, cross-gradient and downgradient of the Mill site and TMS. In addition, carbonaceous

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material has been noted at many locations which is consistent with at least locally reducing
conditions and the existence of pyrite (Table 11).
As discussed in HGC (2012c), samples of selected archived drill core and drill cuttings were
analyzed visually and quantitatively by a contract analytical laboratory. Table 13 and Figure 32
summarize the occurrence of pyrite in site borings based on lithologic logs and laboratory
analyses.
The results of the visual and quantitative analyses verify the site-wide, apparently ubiquitous
existence of pyrite in the perched zone at the site. The existence of pyrite is confirmed at
locations upgradient, cross-gradient, and downgradient of the Mill site and TMS. The results are
consistent with Shawe’s (1976) description of the Dakota Sandstone and Burro Canyon
Formations as “altered-facies” rocks within which pyrite formed as a result of invasion by pore
waters originating from compaction of the overlying Mancos Shale.
Pyrite and/or marcasite were detected in all samples submitted for visual (microscopic) analysis
(Table 12) having pyrite noted in their respective lithologic logs. Pyrite occurs primarily as
individual grains and as a cementing material, and more rarely as inclusions in quartz grains.
Pyrite and/or marcasite were detected in the samples at volume percents ranging from
approximately 0.05 to 25. Grain sizes ranged from approximately one micrometer to nearly
2,000 micrometers. Small grain sizes suggest that much of the pyrite present in the formation
may not be detectable during field lithologic logging of boreholes and that the actual abundance
of pyrite is larger than indicated by the lithologic logs. The detection of marcasite (orthorhombic
crystalline FeS2), which is more reactive than pyrite (cubic crystalline FeS2), is an important
result of the investigation because its reaction rate with either oxygen or nitrate will likely be
higher. The laboratory visual (microscopic) analyses confirm the visual observations made
during field lithologic logging.
Pyrite was detected by quantitative x-ray diffraction (XRD) analysis in samples from MW-3A,
MW-24, MW-26, MW-27, MW-28, and MW-32 at concentrations ranging from 0.1% to 0.8%
by weight (Table 10). Based on the iron content via XRD analysis and the total sulfur analysis,
pyrite may also be present in samples from MW-23, MW-25, and MW-29 at concentrations
ranging from 0.1% to 0.3%. The presence of pyrite is not indicated in MW-30 or MW-31 by
either method of analysis, although it was noted in the lithologic logs. This suggests that the
samples submitted for analysis from these borings may not have been representative, or that
pyrite degraded over time during storage. Except for MW-30 and MW-31, the quantitative
analyses confirm the visual observations made during field lithologic logging.

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Although pyrite was not directly detected by XRD in samples from MW-23, MW-25, or MW-29,
the detected iron and sulfur in these samples is consistent with the presence of pyrite. While at
least a portion of the detected sulfur may result from the gypsum or anhydrite detected in some
of these samples (Table 10), iron not in the form of pyrite would be expected to exist primarily in
the form of iron oxides or perhaps iron carbonates. The absence of detected iron oxides or
carbonates in samples from these borings suggests iron in the form of pyrite.
Furthermore, pyrite was either directly detected or possibly detected based on the presence of
iron and sulfur in samples from MW-3A, MW-23, MW-24, MW-28, and MW-29, which did not
have pyrite noted in the associated lithologic logs. These results are consistent with the small
grain sizes noted via the laboratory visual (microscopic) analysis indicating the absence of pyrite
in a lithologic log does not necessarily mean pyrite is not present in the associated boring, and
that pyrite occurrence at the site has likely been underestimated based on the lithologic logs.
In addition, pyrite was reported in the lithologic log for MW-24A (Appendix A), installed in
2019, and co-located with MW-24.
4.3 Expected Influence of Transient Conditions, Oxygen Introduction, and
the Mancos and Brushy Basin Shales on Dakota/Burro Canyon
Chemistry
Current conditions within the perched groundwater system hosted by the Burro Canyon
Formation and Dakota Sandstone do not approach steady state over much of the monitored area.
A large part of the site perched water system is transient and affected by long-term changes in
water levels due to past and current activities unrelated to the disposal of materials to the TMS.
Changes in water levels have historically been related to seepage from the wildlife ponds;
however past impacts related to the historical pond, and to a lesser extent the sanitary leach
fields, are also expected. Water levels have decreased at many locations due to chloroform and
nitrate pumping and reduced recharge from the wildlife ponds.
The transient nature of a large portion of the perched water system, manifested in long-term
changes in saturated thicknesses and rates of groundwater flow, is expected to result in trends in
pH and in the concentrations of many dissolved constituents that are unrelated to site operations.
Changes in saturated thicknesses and rates of groundwater flow can result in changes in
concentrations of dissolved constituents (or pH) for many reasons. For example, as discussed in
HGC (2012c), groundwater rising into a vadose zone having a different chemistry than the
saturated zone can result in changes in pH and groundwater constituent concentrations. If the rise

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in groundwater represents a long-term trend, long-term changes in groundwater constituent
concentrations (or pH) may result.
Under conditions where vadose zone chemistry is not markedly different from saturated zone
chemistry, changing groundwater flow rates may result in changing constituent concentrations
due to changes in dilution. For example, relatively constant flux of a particular solute into the
groundwater zone, resulting in a relatively constant groundwater concentration under conditions
of steady groundwater flow, will likely result in changing concentrations should groundwater
flow become unsteady. If the change in flow rate is in one direction over a long period of time, a
long-term trend in the solute concentration is expected to result. Examples include oxygen
dissolved in recharge or a constituent present in vadose zone materials overlying perched
groundwater that dissolves in recharge and leaches into perched water at a steady rate. An
increase in perched flow may cause an increase in dilution and a reduction in constituent
concentration and vice-versa. For example, the decrease in dilution related to reduced wildlife
pond recharge has caused increases in dissolved constituent concentrations within the chloroform
plume and, to a lesser extent, the nitrate plume as discussed in Section 3.4.1.2.
Furthermore, the lined cells within the TMS are expected to act as barriers to natural recharge
and exchange of gas with the atmosphere; their mere presence may thus result in changes in
perched water chemistry. Any such changes are likely to be relatively slow and in one direction,
potentially yielding long term trends in parameter values.
The perched groundwater chemistry at the Mill is also expected to be impacted by the following
factors:
1. The relatively low permeability of the perched zone. This condition increases
groundwater residence times and the time available for groundwater to react with the
formation.
2. The location of the perched system between two shales, the underlying Brushy Basin
Member of the Morrison Formation and the overlying Mancos Shale. Both are potential
sources of numerous dissolved constituents. Potential interaction between the Brushy
Basin Member and perched water are discussed in TITAN (1994). The potential for
natural contamination from the Mancos Shale is discussed in USDOE (2011).
3. The rate of interaction between the Mancos and Brushy basin Member shales and the
perched water. Interaction with the Mancos Shale at any particular location will depend
on the presence, thickness, and composition of the Mancos, the rate of recharge through
the Mancos into the perched zone, and the saturated thickness and rate of groundwater
flow in the perched zone. Interaction with the Brushy Basin Member at any particular
location will depend on the composition of the Brushy Basin, and the saturated thickness
and rate of flow in the perched zone. Oxygen introduced into site monitoring wells may

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also react with the Brushy Basin Member and affect the chemistry of perched
groundwater in contact with the Brushy Basin.
4. The rate of oxygen introduction into the perched zone via recharge or via site
groundwater monitoring wells. Introduced oxygen is available to oxidize constituents
such as pyrite, which impacts the local groundwater chemistry near each recharge source
and near each well by releasing acid and sulfate. The resulting increased acidity can also
destabilize various mineral phases in the aquifer matrix. The degree of impact on perched
groundwater chemistry will depend on the amount of pyrite, the rate of oxygen transfer,
the neutralization capacity and saturated thickness of the perched zone, and the rate of
groundwater flow.
5. Elements other than iron and sulfur as contaminants in pyrite. Pyrite reacting with oxygen
introduced into the formation will release these elements, potentially altering both the
vadose zone and the groundwater chemistry. The likelihood of pyrite having significant
contaminants (such as selenium) is enhanced considering its origin from fluids expelled
from the Mancos Shale. As discussed in EFRI (2021b), bottle-roll tests using pyrite-
bearing core from the formation hosting perched groundwater at the site yielded bottle-
roll solutions initially consisting of laboratory-grade DI water generating as much as 74
µg/L beryllium; 118 µg/L cadmium; 79 µg/L cobalt; 959 µg/L copper; 4,120 µg/L
manganese; 278 µg/L nickel; 303 µg/L selenium; 2.3 µg/L thallium; 6,700 µg/L uranium;
and 1,680 µg/L zinc; as well as elevated concentrations other constituents.

Changes in perched zone constituent concentrations and pH are therefore expected to result from
the introduction of oxygen into the subsurface, the oxidation of pyrite and other constituents,
changes in recharge rates, and past and current recharge passing through the Mancos Shale.
Selenium is an example of a constituent that: is naturally occurring in the Burro Canyon
Formation; is elevated in the Mancos Shale; and is a common contaminant in pyrite. That the
Mancos Shale is a significant source of selenium is discussed in Baker, (2007); Colorado
Department of Health and Environment (2011); (Tuttle, 2005); and USDOE (2011).
Because the Mancos overlies the perched zone over much of the site (Figures 11A and 11B) it
could represent a past and ongoing source of selenium (as wells as other constituents). Selenium
originating from the Mancos Shale could potentially increase concentrations in the perched zone
by three mechanisms: 1) ongoing leaching from the Mancos Shale via recharge; 2) oxidation of
Mancos-derived selenium in the Burro Canyon Formation and Dakota Sandstone by dissolved
nitrate in the perched water and/or oxygen introduced into the perched zone via perched well
casings; and 3) oxidation of pyrite containing Mancos-derived selenium by dissolved perched
zone nitrate and/or oxygen introduced into the perched zone via perched well casings. Selenium
already present in the Dakota Sandstone and Burro Canyon Formation (including as a constituent

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in pyrite) could have originated from the Mancos Shale in the past, and could affect the entire
formation rather than just the areas beneath the current erosional remnants of the Mancos.
Precipitation percolating downward from the land surface is expected to leach selenium from the
Mancos Shale and carry it downward into the perched zone. Beneath the TMS, any such leaching
is expected to have occurred for the most part prior to the installation of the individual cells
which represent barriers to infiltration of precipitation. Vadose pore waters in the Dakota
Sandstone and Burro Canyon Formation beneath the TMS may thus be expected to contain
selenium leached from the Mancos in the past. Perched water rising into vadose pore waters
containing selenium may enhance mass transfer and result in increased selenium concentrations
in the perched water.
Potentially increasing selenium concentrations may also result from the oxidation of selenium
already present in the Dakota Sandstone and Burro Canyon Formation. Oxidation of selenium by
nitrate present in perched water and/or by oxygen introduced into the formation via the well
casings may result in increasing dissolved selenium concentrations. The possibility of nitrate
oxidation of selenium is presented in Potoroff (2005).
A third potential source for increasing dissolved selenium concentrations in perched water is
oxidation of pyrite by nitrate and/or oxygen introduced into the formation via well casings.
Pyrite typically contains trace elements including selenium. Selenium has been measured at
concentrations as high as 0.2% by weight in pyrite (Deditius, 2011). As discussed in HGC
(2012c), pyrite oxidation is expected to result in other changes that include an increase in
dissolved sulfate (unless a sink for sulfate is present). Oxidation of pyrite by dissolved oxygen is
expected to result in a decrease in pH as acid is released in the reaction:
FeS2 + 33/4O2 + 31/2H2O = Fe(OH)3 + 2SO42- + 4H+

Oxidation of pyrite by nitrate may also occur as discussed in HGC (2012c). This process may
result in either an increase or decrease in pH depending on the reaction pathway:
5 FeS2 + 14NO3- + 4H+ = 7N2 + 10SO42- + 5Fe2+ + 2H2O; or

2 FeS2 + 6NO3- + 2H2O = 3N2 + 4SO42- + 2FeOOH + 2H+

The interaction between nitrate and pyrite will be discussed in more detail in the following
Section.
Furthermore, constituents other than selenium that are elevated in the Burro Canyon Formation
due to past invasion of pore waters from the Mancos Shale, or that exist as contaminants in

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pyrite, can be released as a result of geochemical changes unrelated to disposal of materials to
the TMS (such as increases in oxygen and nitrate), causing trends in concentrations of these
constituents in site monitoring wells. As discussed above, other potential constituents include
(but are not limited to) beryllium, cadmium, cobalt, copper, manganese, nickel, thallium,
uranium, and zinc.
4.4 Implications for Perched Water Chemistry and Natural Attenuation of
Nitrate and Chloroform
As discussed above, past, current, and future interaction of the perched groundwater zone with
the overlying Mancos Shale and underlying Brushy Basin Member can be expected to affect
perched water chemistry at the site. Changes in perched water chemistry related to oxidation of
pyrite by oxygen introduced into the subsurface dissolved in recharge and via well casings is also
expected to occur.
Concentrations of chloroform and nitrate already present in the perched zone will be affected
over time by various processes, including direct mass removal by pumping. Natural attenuation
of both constituents is expected to result from physical processes that include dilution by
recharge and hydrodynamic dispersion. Volatilization into the vadose zone is another physical
process that is expected to lower chloroform concentrations in perched water. Mass reduction
processes expected to lower both nitrate and chloroform concentrations include chemical and
biologically-mediated processes. The impacts of pyrite degradation by oxygen, degradation of
nitrate by pyrite, and reductive dechlorination of chloroform are discussed in Sections 4.4.1
through 4.4.3.
4.4.1 Pyrite Degradation by Oxygen
As discussed in HGC (2012c), the pH values measured in many site groundwater monitoring
wells located upgradient, within the vicinity of, and downgradient of the Mill site and TMS
displayed decreasing trends. pH decreases in many of these wells were accompanied by increases
in sulfate concentrations. Ten of the MW-series groundwater monitoring wells were previously
out of compliance (OOC) with respect to pH due to a decreasing trend.
As discussed in INTERA (2012a and 2102b) and Section 5 below, changes in pH were
determined to result from natural causes unrelated to the operation of the TMS. Based on work
described in HGC (2012c), the decreases in pH and increases in sulfate in OOC wells were
explainable by oxidation of pyrite, which releases acid and sulfate as described above.
Screening-level calculations and geochemical modeling using PHREEQC (Parkhurst and

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Appelo, 1999) indicated that pyrite measured in samples from the perched zone existed in more
than sufficient quantity to have resulted in the measured changes in pH and sulfate at three
representative wells located immediately upgradient (MW-27), immediately downgradient (MW-
24), and far downgradient (MW-3A) of the TMS. The calculations also indicated that pyrite
existed in sufficient quantity to maintain these trends provided sufficient oxygen was available.
Furthermore, site dissolved oxygen measurements since the third quarter of 2019 confirm that
there is sufficient oxygen available to oxidize pyrite and produce acid and sulfate. Continued
release of any contaminants within site pyrite was expected as was the release of pH sensitive
constituents present in the Burro Canyon Formation and Dakota Sandstone.
Although decreasing pH trends occurred in nearly all MW-series wells until about 2016, pH
began to stabilize and then increase. The pH increase cannot result from a TMS impact because
TMS solutions have very low pH. The post-2016 increasing pH trends indicate that TMS
operation has not impacted groundwater.
4.4.2 Nitrate Degradation by Pyrite
As discussed in HGC (2012c), nitrate will degrade in the presence of pyrite. Nitrate will also
degrade, and more readily, in the presence of organic matter. Both pyrite and organic material in
the form of carbonaceous matter have been logged in drill cuttings from the perched groundwater
zone.
As discussed in (Korom, 1992), the thermodynamically favored electron donor for reduction of
nitrate in groundwater is typically organic matter. This process under neutral conditions is
represented via the following generalized reaction (e.g. van Beek, 1999; Rivett et al., 2008;
Tesoriero and Puckett, 2011; Zhang, 2012):
2 3 2 3 2 3 2
5 4 2 4 2CH O NO N HCO H CO H O
- -+ = + + +(Reaction 1);

In acidic (pH < 6.4) aquifer conditions, reduction of nitrate by organic matter can be generalized
by the following pathway:
2 3 2 2 3 2
5 4 4 2 5 2CH O NO H N H CO H O
- ++ + = + +(Reaction 2).

In both cases, five moles of organic matter are required to reduce four moles of nitrate. Under
acidic conditions the alkalinity generated by denitrification by organic matter consumes acid.

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In the absence of dissolved oxygen, pyrite can also be oxidized by nitrate. Denitrification by
pyrite may occur via two primary reaction pathways. The pathway most commonly applied in
geochemical studies (Kolle et al., 1983, 1985; Postma et al., 1991; Korom, 1992; Robertson et
al., 1996; Pauwels et al., 1998; Hartog et al., 2001, 2004; Spiteri et al., 2008) is a bacteria-
mediated reaction that yields ferrous iron, sulfate, water, and nitrogen gas as follows:
2 2
2 3 2 4 2
5 14 4 7 10 5 2FeS NO H N SO Fe H O
- + - ++ + = + + + (Reaction 3).

By Reaction 3, five moles of pyrite reduce 14 moles of nitrate, consuming four moles of acid.
Reaction 3 is considered applicable when pyrite concentrations exceed nitrate concentrations
(van Beek, 1999). Where nitrate concentrations exceed pyrite concentrations, Reaction 4 is a
more likely mechanism (Kolle et al., 1987; van Beek, 1999; Schlippers and Jorgensen, 2002):
2
2 3 2 2 4 3
2 6 4 3 4 2 ( ) 2FeS NO H O N SO Fe OH H
-- ++ + = + + +(Reaction 4).

By Reaction 4, two moles of pyrite reduce six moles of nitrate, yielding iron hydroxide, sulfate,
acid, and nitrogen gas. Therefore, when nitrate concentrations exceed pyrite concentrations
(Reaction 4), denitrification by pyrite is more efficient than when pyrite is in excess (Reaction
3). Additionally, Reaction 4 produces acid, while Reaction 3 consumes acid, indicating that the
impact of denitrification by pyrite on aquifer geochemistry is controlled by the relative
abundance of pyrite and nitrate; and that pH may decrease or increase depending on the reaction
pathway.
Reaction 4 is an overall reaction that combines Reaction 3 and a second step whereby ferrous
iron is oxidized by nitrate. This second step is more likely to occur when excess nitrate is present
and available to oxidize ferrous iron (Kolle et al., 1987; Rivett et al., 2008; Zhang 2012).
Stoichiometric calculations were used to determine the weight percent of perched zone pyrite
that would be required to reduce the ‘baseline’ estimate of 43,700 lbs of nitrate (HGC, 2012a)
via reaction mechanisms 3 and 4 (assuming each was the only denitrification reaction occurring).
43,700 lbs of nitrate corresponds to 19,822 kg and 319,684 moles. Although organic matter is
noted in lithologic logs, the organic matter content of the perched zone has not been quantified
so calculations regarding nitrate degradation by reactions 1 and 2 are not presented, even though
significant nitrate reduction via these mechanisms is likely to occur.
Nitrate can either migrate towards Ruin Spring to the south-southwest or to Westwater Seep to
the west. Assuming the entire nitrate plume migrated south towards Ruin Spring, the volume of
the perched zone through which the nitrate plume would migrate was assumed to be on average

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20 feet thick, 1,200 feet wide, and 10,000 feet long, representing a total saturated formation
volume of 2.4 x 108 ft3 or 6.8 x 109 liters. Assuming the entire nitrate plume migrated west
toward Westwater Seep, the volume of the perched zone through which the nitrate plume would
migrate was assumed to be on average 18 feet thick, 2,800 feet wide, and 4,950 feet long,
representing a total saturated formation volume of 2.5 x 108 ft3 or 7 x 109 liters. To be
conservative, the following calculations are based on the smaller volume of 6.8 x 109 liters.
Using these estimates, reaction 3 would require 114,173 moles of pyrite to consume 43,700 lbs
of nitrate, and would consume 91,338 moles of acid (1.34 x 10-5 moles H+ per liter of formation).
Reaction 4 would require 106,561 moles of pyrite to degrade the nitrate, producing 106,561
moles of acid or 1.57 x 10-5 moles H+ per liter of formation.
Assuming a conservatively large porosity of 0.2 for the perched zone (HGC, 2012c), the total
volume of water is 1.36 x 109 liters; and assuming a solids density of 2.6 kg L-1, yields a total
solid mass of 1.4 x 1010 kg.
Using this solid mass, both Reactions 3 and 4 would require pyrite formation weight percents of
0.000098% (9.8 x 10-5 %) and 0.000091% (9.1 x 10-5 %), respectively, to degrade 43,700 lbs of
nitrate.
These calculated pyrite weight percents are orders of magnitude less than conservative estimates
of pyrite content based on samples analyzed during the pyrite investigation (HGC, 2012c), which
ranged from 0.0056% to 0.08% (5.6 x 10-3 % to 8 x 10-2 %). These results suggest that the
available pyrite content in the path of the nitrate plume is two to three orders of magnitude
greater than needed to degrade the total mass (43,700 lbs) of nitrate. These calculations are
conservative in that they assume the degradation of the entire mass of nitrate and not just the
mass needed to reduce concentrations below 10 mg/L. Whether or not pyrite oxidation by nitrate
at the site is generating or consuming acid depends largely on whether oxidation of ferrous iron
by nitrate is occurring (i.e. whether pyrite denitrification is occurring by Reaction 3 or Reaction
4; whether nitrate exists in excess).
The preferred mechanism for denitrification by pyrite is likely to vary spatially. If pyrite is
assumed to be relatively evenly distributed throughout the formation, while nitrate occurs in a
discrete plume, Reaction 3 may dominate on the plume edges while Reaction 4 may dominate
the core of the plume.
As discussed in HGC (2017), estimated average natural nitrate degradation rates range from
approximately 172 lb/yr to 200 lb/yr (or approximately 5.4 x 10-6 pounds per cubic feet per year
[lb/ft3 yr] to 6.4 x 10-6 lb/ft3 yr). These estimates conservatively ignore the much higher rates

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calculated in HGC (2017) using ‘Method 2’, which yielded nitrate degradation rates as large as
9 x 10-5 lb/ft3 yr. Based on the third quarter, 2021 residual nitrate plume mass estimate of
approximately 28,290 lb, and assuming natural nitrate degradation rates of 172 lb/yr to 200 lb/yr,
less than 200 years would be required to remediate the nitrate plume, even in the absence of any
direct mass removal by pumping.
4.4.2.1 Other Relevant Studies Regarding Nitrate Reduction by Pyrite
Nitrate degradation by pyrite is a well-known mechanism discussed extensively in the literature.
USEPA (2007) recognizes the importance of pyrite-bearing aquifers in reducing or eliminating
nitrate contamination, stating that “pyrite-bearing aquifers represent important hydrological
compartments due to their capacity to eliminate nitrate.”
Other relevant excerpts from available literature are provided below:
• Jioyang (2014) indicates that pyrite is suitable for nitrate remediation with a nitrate
removal rate constant of 0.95/day.
• Krieger (2014) indicates that “the major electron donors for denitrification are organic
carbon (OC), pyrite (FeS2) and ferrous iron silicate minerals. In the […] tracer tests,
increases in sulfate indicated that the oxidation of pyrite explained a significant
[proportion] of the denitrification.”
• Zhang (2012) indicates that “Pyrite oxidation leads to sulfate production and trace metal
release to groundwater. This process can have a major impact on local and regional water
quality.”
• Zhang (2012) also indicates that “denitrification with pyrite can be the dominant pathway
of nitrate removal from groundwater, even when organic matter is present.”
• Zhang (2009) concludes that “nitrate removal from the groundwater below cultivated
fields correlates with sulfate production, and the release of dissolved Fe2+ and pyrite-
associated trace metals (e.g. As, Ni, Co and Zn). These results, and the presence of pyrite
in the sediment matrix within the nitrate removal zone, indicate that denitrification
coupled to pyrite oxidation is a major process in the aquifer.”
• Tesoriero (2011) indicates that “A review of published rates suggests that denitrification
tends to occur more quickly when linked with sulfide oxidation than with carbon
oxidation.”
• Bosch (2011) states “Here, we provide evidence for the capability of Thiobacillus
denitrificans to anaerobically oxidize a putatively nanosized pyrite particle fraction with
nitrate as electron acceptor. Nanosized pyrite was readily oxidized to ferric iron and
sulfate with a rate of 10.1 μM h-1. The mass balance of pyrite oxidation and nitrate
reduction revealed a closed recovery of the electrons. This substantiates a further
‘missing lithotrophy’ in the global cycles of sulfur and iron and emphasizes the high
reactivity of nanominerals in the environment.”

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• Aguerri (2010) identified areas within the Osona region of Spain where, based on
hydrogeological and multi-isotopic methods, nitrate degradation via pyrite oxidation was
occurring.
• Torrento (2010) indicates that “Nitrate reduction was satisfactorily accomplished in
experiments with pyrite as the sole electron donor, in presence of the autotrophic
denitrifying bacterium Thiobacillus denitrificans and at nitrate concentrations comparable
to those observed in contaminated groundwater. The experimental results corroborated
field studies in which the reaction occurred in aquifers.”
• Jorgensen (2009) concludes that microbes can control groundwater nitrate concentrations
by denitrification “using primarily pyrite as electron donor at the oxic-anoxic boundary in
sandy aquifers.”

Note the potentially important impacts on water quality resulting from the trace metal and sulfate
release from pyrite oxidation as discussed in Zhang (2009; 2012). In addition, as discussed
above, depending on the particular reaction pathway, acid may also be released causing a
decrease in pH resulting in mobilization of additional metals.
4.4.2.2 Comparison to Oostrum Site
Bosch and Meckenstock (2012) discuss degradation of nitrate via pyrite oxidation in field and
laboratory studies and provide calculated rates. These rates are summarized in Table 14. Of
particular interest are the rates calculated for the Oostrum, Netherlands site, an agricultural area
which overlies a pyritic sandy aquifer. The Oostrum site is discussed in detail in Zhang (2009)
and Zhang (2012).
Similarities between the Oostrum and Mill sites include:
• Sandy materials containing pyrite host groundwater;
• Locally anaerobic conditions are present (inferred at Mill from detectable chloroform
daughter product concentrations and persistence of pyrite);
• Similar pyrite concentrations (from <0.1 to approximately 0.8 wt% at both sites; and
similar average concentrations as shown in Tables 14 and 15);
• Calculated nitrate (as nitrogen) degradation rates at the Mill that are similar to, but lower
than the rate calculated for the Oostrum site (approximately 5.4 x 10-4 lb/ft3-yr at
Oostrum; and approximately 5.4 x 10-6 to 6.35 x 10-6 lb/ft3 yr at the Mill as shown in
Table 15).

The rate reported for the Oostrum site, which has pyrite concentrations that are similar to those
measured at the Mill, is one to two orders of magnitude higher than the rates calculated for the

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Mill, suggesting that the rates calculated for the Mill are conservatively low and may
underestimate actual rates.
Regardless, as discussed in Section 3.8, even in the absence of any nitrate reduction by pyrite or
mass removal via pumping, numerical flow and transport modeling using conservative
assumptions indicates that natural attenuation will reduce all nitrate concentrations within the
plume to less than the 10 mg/L GCAL before reaching a property boundary.
4.4.3 Chloroform Reduction
As discussed in HGC (2007b) and HGC (2022), the presence of chloroform daughter products
indicates that chloroform is degrading naturally via reductive dechlorination. Calculations
presented in HGC (2022) based on daughter product concentrations indicated that the entire
chloroform plume would be reduced to concentrations below the GCAL of 70 ug/L within
approximately 168 years or less, even in the absence of any direct mass removal by pumping.
Reductive dechlorination takes place under anaerobic conditions which were inferred to exist
only locally within the perched zone. The low rates of degradation and the persistence of nitrate
associated with the chloroform plume are consistent with primarily aerobic conditions.
However, the widespread occurrence of pyrite in the perched zone is consistent with at least
locally anaerobic conditions, and with the relatively low calculated rates of chloroform
degradation presented in HGC (2007b) and HGC (2022). Continued reductive dechlorination is
expected within locally anaerobic portions of the perched zone.

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5. SUMMARY OF PERCHED GROUNDWATER MONITORING AND
STUDIES
As noted in Section 2.0, investigations to date and more than 41 years of perched groundwater
monitoring indicate that operation of the Mill has not impacted perched groundwater. A detailed
list of studies and the associated reports is included in Section 2.0 and in Section 1.0 of the 2022
Groundwater Discharge Permit Renewal Application.
Specifically, background groundwater quality evaluations have been performed for each MW-
series groundwater monitoring well. These wells are located within the Mill site and cells
comprising the TMS as well as up-gradient, downgradient and cross-gradient of these facilities.
Groundwater compliance limits (GWCLs) have been established for each Groundwater
Discharge Permit (GWDP) constituent on an intra-well basis. Compliance limits are calculated
on an intra-well basis because of the large variation in background water quality within the
perched groundwater zone.
The Background Quality Reports completed prior to 2010 (INTERA, 2007a and 2007b;
collectively the Background Reports), evaluated groundwater analytical data collected since the
initiation of groundwater sampling and in the wells installed as specified in the DWMRC GWDP
respectively. The Background Reports identified naturally occurring elevated, increasing, and
decreasing concentrations of various constituents in monitoring wells located far upgradient, far
downgradient, far cross-gradient and in the vicinity of the Mill site and TMS. Increasing
concentration trends identified by INTERA were present at the time that an isotopic investigation
by the University of Utah (Hurst and Solomon, 2008) concluded that there were no impacts to
groundwater from the TMS. The isotopic study provided additional confirmation that the
identified constituent trends were the result of natural background influences unrelated to
disposal of materials to the TMS.
Additional Background Reports have been completed for wells installed after the completion of
the 2007 and 2008 studies. These Background analyses for wells MW-20, MW-22, MW-35,
MW-36, MW-37, MW-38, MW-39 and MW-40 support previous conclusions that the
groundwater at the Mill is not being affected by disposal of materials to the TMS.
Per the GWDP, constituents with two consecutive GWCL exceedances are subject to a Source
Assessment Report (SAR) as defined in the GWDP. The initial SAR was submitted in October of
2012 (INTERA 2012a) and covered all of the constituents in wells with consecutive exceedances
since the approval of the GWDP in 2010. The October 2012 SAR (INTERA 2012a) presented a
geochemical analysis of parameters that exhibited exceedances as well as an analysis of indicator

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parameters (chloride, fluoride, sulfate and uranium) to determine if the exceedance could be
related to potential TMS seepage or Mill-related activities. Since then, twelve additional SARs
prepared by INTERA (INTERA 2013a; 2013b; 2014a; 2014b; 2015; 2016; 2017; 2018; 2019a;
2019b; 2019c; and 2020); and five SARs prepared by EFRI (EFRI, 2020; 2021a; 2021c; 2022a;
and 2022d) cover additional consecutive exceedances. In all cases the exceedances for which the
SARs were performed were determined to result from naturally occurring conditions in the
groundwater at the site or from other factors that are affecting groundwater but are unrelated to
TMS operation. These other factors include the nitrate/chloride plume that extends
approximately 1,000 feet upgradient (north-northeast) of the TMS (and is addressed by the
nitrate CAP); a sitewide decline in pH that was identified at the time of the Background Report;
as well as other natural background factors unrelated to disposal of materials to the TMS. Further
study of the natural background factors affecting the groundwater at the site have been
undertaken by EFRI and are discussed below.
At the time of the Background Report, an overall decline in pH across the site was observed.
Background analysis and determination of GWCLs for pH were performed using laboratory pH
measurements rather than using measurements that are collected in the field at the time of
sampling by using a pH probe. Since the latter of these two methods of measuring pH is more
reliable, an additional pH analysis was performed in 2012 using only field data. GWCLs for pH
were recalculated at this time using the field measurements. As discussed in Section 4.4.1, HGC
(2012c) determined that pH decreases resulted from oxidation of naturally-occurring pyrite
enhanced by oxygen delivery to the perched zone. Oxygen delivery mechanisms included
advective transport to the perched zone dissolved in wildlife pond seepage, and diffusive and
dispersive transport to perched groundwater in the vicinities of perched wells via perched well
casings. In addition, pH decreases at wells impacted by the nitrate plume could result from
nitrate degradation of pyrite by the reaction mechanism that produces, rather than consume, acid
as discussed in Section 4.4.2. pH decreases have therefore been determined to be unrelated to
TMS operation.
Furthermore, although the pH decrease was an apparently site-wide phenomenon, since about
2016, pH in nearly all MW-series wells has stabilized and has begun to increase. As discussed in
EFRI (2022a) and EFRI (2022d), because TMS solutions have very low pH, the post-2016
increases indicate that TMS solutions cannot be impacting groundwater.
5.1 Chloroform Plume
As discussed in Section 2, a chloroform plume occurring within shallow perched groundwater at
the Mill has been under remediation by pumping since 2003 (HGC, 2007a). The chloroform

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plume is located generally cross- to up-gradient of the TMS (HGC, 2007b and Figure 1B). The
2022 Corrective Action Comprehensive Monitoring Evaluation (CACME) report for the
chloroform plume (HGC, 2022) represents a 2-year review of the Corrective Action as required
by Part III.H of the Groundwater Corrective Action Plan (GCAP) found in Attachment 1, of the
final Stipulation and Consent Order (“SCO”) Docket No. UGW20-01 (Utah Department of
Environmental Quality Division of Solid Waste and Radiation Control, 2015).
As discussed in the chloroform CACME the chloroform plume is under control. Current
pumping system effectiveness is demonstrated by 1) the slowing to near halting of plume
boundary expansion attributable to reduced dilution from reduced wildlife pond recharge and
redistribution of chloroform resulting from nitrate pumping; and 2) the maintenance of a large
proportion of the plume mass under hydraulic capture (approximately 97% as of the fourth
quarter of 2021). High rates of capture have been maintained even considering reduced
productivities at some of the pumping wells and the failure and subsequent abandonment of
pumping well TW4-20 during 2020. The abandonment of TW4-20 had little to no measurable
impact on pumping, mass removal rates, and capture in the vicinity of TW4-20, as increases in
pumping at TW4-19 subsequent to TW4-20 failure more than compensated for the loss of
pumping at TW4-20.
As discussed in Section 4.4.3 and Appendix C of the CACME, natural attenuation calculations
suggest that all chloroform concentrations will be below the GCAL of 70 ug/L within less than
200 years, not taking into account the effects of any direct mass removal by pumping. Using the
average calculated chloroform degradation rate (Appendix C of the CACME), the highest 2021
chloroform concentration of 14,800 µg/L would be reduced to the GCAL of 70 µg/L within
approximately 61,353 days or 168 years, even in the absence of pumping. If the degradation rate
is based only on data collected from pumping well MW-26, which has chloroform concentrations
close to the average chloroform concentration for the plume, the time to reduce the highest 2021
concentration of 14,800 µg/L to the GCAL of 70 µg/L would take approximately 16,890 days or
only 46 years.
5.2 Nitrate Plume
As discussed in Section 2, the nitrate plume has been under remediation by (Phase II) pumping
since the first quarter of 2013. The plume, defined by groundwater concentrations exceeding 10
mg/L nitrate as nitrogen, originates upgradient (northeast) of the TMS at the site (HGC, 2017
and Figure 1B). Likewise, the commingled chloride plume, defined by groundwater
concentrations exceeding 100 mg/L chloride, also originates upgradient of the TMS.

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The 2017 Corrective Action Comprehensive Monitoring Evaluation (CACME) report for the
nitrate plume (HGC, 2017) represents a 5-year review of the Phase II Corrective Action as
specified in the final Stipulation and Consent Order (SCO) Docket No. UGW12-04 (Utah
Department of Environmental Quality Division of Solid Waste and Radiation Control, 2012). As
discussed in the nitrate CACME, between the second quarter of 2010 and the third quarter of
2017, the mass of nitrate contained within the plume has been reduced by approximately 11% to
25%. Based on data presented in EFRI (2022c), the residual mass of the nitrate plume has
continued to decline. Furthermore, as discussed in Section 4.4.2, there is enough pyrite in the
perched zone within the path of the nitrate plume to completely attenuate the plume through
natural reduction of nitrate alone. As discussed in HGC (2017) and Section 4.4.2, estimated
natural nitrate degradation rates range from approximately 172 lb/yr to 200 lb/yr, indicating that
less than 200 years would be required to remediate the nitrate plume, even in the absence of any
direct mass removal by pumping. However, considering both pumping and estimated natural
attenuation rates presented in HGC (2017), the mass of the plume is expected to be reduced by
approximately 573 to 601 lb/yr, and nitrate concentrations within the plume are expected to be
reduced to negligible values (less than 10 mg/L) within approximately 54 to 57 years. As the
estimated time for impacted water to reach the nearest discharge point (Westwater Seep or Ruin
Spring) is greater than 3,000 years, there is no concern at this time that the continuation of
current corrective actions will not result in remediation of the plume well before it can reach any
exposure to the public or wildlife.
In response to a DWMRC request, additional attenuation modeling of the nitrate plume was
conducted to further study and refine the conclusions presented in the 2017 nitrate CACME.
Accordingly, a Phase III Planning Document was prepared (HGC 2018e).
The Phase III planning document included conceptual-level numerical groundwater flow and
solute transport assessments to evaluate the maximum distance that the nitrate plume could
travel, assuming hypothetical ‘worst-case’ conditions, before all concentrations are reduced
below 10 mg/L, indicating that full attenuation has occurred.
These ‘worst-case’ transport assessments:
1. Disregard the natural degradation of nitrate within the plume via pyrite oxidation which
will cause overestimation of simulated plume migration;
2. Disregard the (relative) stability of the southern (downgradient) margin of the nitrate
plume which suggests that pumping and natural attenuation processes are minimizing or
preventing plume expansion to the south;

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3. Disregard nitrate mass removal by pumping and natural dilution of nitrate concentrations
via recharge by precipitation, which will cause overestimation of simulated plume
migration;
4. Substantially overestimate hydraulic conductivities (by as much as two orders of
magnitude) and hydraulic gradients (by nearly a factor of two) downgradient of the TMS,
which will cause substantial overestimation of simulated plume migration rates; and
5. Underestimate dispersivities which will cause underestimation of hydrodynamic
dispersion and overestimation of simulated plume migration.

The conceptual-level transport assessments indicate that the nitrate plume will not migrate
beyond the site property boundary or to a discharge point before fully attenuating, even under
hypothetical ‘worst-case’ assumptions. Therefore, under any currently conceivable conditions,
including hypothetical ‘worst-case’ conditions that greatly overestimate plume migration rates,
underestimate mechanical dispersion, and disregard mass removal by pumping and natural
degradation, there will be no expected hazard to public health, safety or the environment; no
expected exposure to the public, wildlife or the environment; and, as a result, no additional
hazard or exposure assessments are needed at this time.
In summary, the assessments provided in Section 4.4.2 and the 2017 nitrate CACME indicate
that the plume would fully degrade via natural pyrite oxidation alone before reaching a discharge
point. This degradation would occur within 200 years assuming no pumping, dilution by natural
recharge, or hydrodynamic dispersion. The conceptual-level transport assessments performed in
2019 indicate that, even without mass removal via pyrite oxidation or pumping, and assuming
hypothetical ‘worst case’ conditions regarding future nitrate transport, the plume will fully
attenuate before reaching the site property boundary or a discharge point.
5.3 MW-24A Study
As noted above, Part I.G.2 of the GWDP provides that out-of-compliance status exists when the
concentration of a constituent in two consecutive samples from a compliance monitoring point
exceeds a GWCL in Table 2 of the GWDP. As part of the assessment of exceedances of
previous GWCLs, increasing trends in several constituents in MW-24 and other MW-series wells
were observed as noted in the Background Repots and SARs listed above and in Section 2.
In response to the previously identified exceedances and increasing trends, in 2020 EFRI
voluntarily completed a study of MW-24A (collocated with MW-24 as shown in Figure 1A) to
determine what geochemical and hydrogeological influences may be impacting monitoring data
collected at these two wells and potentially other wells across the Mill site. The MW-24A study

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and report (EFRI, 2021b) included several additional field data collection and analytical
activities based on the conclusions of other Mill reports. Tests included whole-rock and synthetic
precipitation leaching procedure (SPLP) analysis of drill core; bottle-roll tests on drill core noted
to have pyrite; and bottle roll tests on ‘pure’ pyrite obtained from a rock shop.
The results of the analytical and other test data collected during the MW-24A study
demonstrated that natural processes unrelated to disposal of materials in the TMS can account for
the behavior of all trace metals of concern, as well as fluoride, in groundwater at MW-24 and
MW-24A. Bottle-roll test results indicated that naturally-occurring trace metals can be mobilized
at concentrations similar to or greater than in groundwater even without a large pH decrease,
suggesting that agitation alone, such as would occur during routine purging and sampling of low
permeability wells such as MW-24A, could result in metals mobilization. Test results are
consistent with average crustal abundances of trace metals detected in some site groundwater
monitoring wells; and with the formations hosting the perched groundwater (Dakota Sandstone
and Burro Canyon Formation) having been impacted by past invasion of pore waters from the
overlying Mancos Shale as discussed in Shawe (1976).
For example, Fleisher (1953) reports the following estimated average crustal abundances of
various metals converted to parts per billion (ppb) by weight: cadmium (100 to 5,000 ppb);
beryllium (5,000 to 30,000 ppb); thallium (0.8 to 600 ppb); cobalt (10,000 to 40,000 ppb); nickel
80,000 to 200,000 ppb); selenium (30 to 800 ppb); and uranium (200 to 9,000 ppb). There is no
compelling reason to suppose that these elements would not naturally be present in the perched
water-bearing Burro Canyon Formation and Dakota Sandstone beneath the Mill. Some or all of
these metals have been detected in far upgradient and far cross-gradient wells that could not have
been impacted by the TMS.
In addition, as discussed in Sections 3.1.3, 3.1.4 and 4.3, the Mancos Shale directly overlying
these formations is anomalous in many metals including selenium and uranium ( USDOE, 2011).
Furthermore, as discussed in Shawe (1976), the Dakota and Burro Canyon are considered
‘altered facies’ rocks primarily as a result of the invasion of pore waters expelled from the
overlying Mancos Shale during compaction that caused removal of hematite coatings on sand
grains, destruction of detrital black opaque minerals, and the growth of iron sulfide minerals such
as pyrite. Not only were the metals contents of the Dakota and Burro Canyon increased by the
invasion of Mancos Shale pore waters, the pyrite created as a result of invasion of these solutions
is expected to contain significant trace metals including selenium. As discussed in Deditius et al
(2011) pyrite commonly contains arsenic (As), lead (Pb), antimony (Sb), bismuth (Bi), copper
(Cu), cobalt (Co), nickel (Ni), zinc (Zn), gold (Au), silver (Ag), selenium (Se) and tellurium
(Te). Oxidation of pyrite by oxygen introduced into the formation via wells or wildlife pond

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seepage, or by nitrate within the nitrate/chloride plume (which originates upgradient of the Mill
and TMS) is expected to directly release these metals to groundwater.
Furthermore, the Dakota Sandstone and Burro Canyon Formation host naturally-occurring
uranium mineralization (Pierson and Greene, 1980; Craig, 1982) that is expected to be mobilized
in the presence of oxygen and/or nitrate. Rose and Wright (1980) indicate that elements
associated with sandstone-type uranium deposits include sulfur (S), vanadium (V), molybdenum
(Mo), Se, As, Cu, Ag, chromium (Cr), Pb, Zn, Ni, Co, rhenium (Re), beryllium (Be),
phosphorous (P), manganese (Mn) and rare earths.
Overall, considering that the Dakota Sandstone and Burro Canyon Formation have been
impacted by the Mancos Shale, and that uranium mineralization with associated elements occurs
naturally within these formations, it is likely that the concentrations of many or all of these
metals exceed average crustal abundances, which appears consistent with the results of the MW-
24A study. As discussed in Section 4.3, bottle-roll tests using pyrite-bearing core from MW-24A
yielded bottle-roll solutions initially consisting of laboratory-grade deionized (DI) water
generating as much as 74 µg/L Be; 118 µg/L cadmium (Cd); 79 µg/L Co; 959 µg/L Cu; 4,120
µg/L Mn; 278 µg/L Ni; 303 µg/L Se; 2.3 µg/L thallium (Tl); 6,700 µg/L U; and 1,680 µg/L Zn;
as well as elevated concentrations other constituents
5.4 Proposed Phase 2 Study
As noted in Section 4.3, the perched groundwater system hosted by the Burro Canyon Formation
and Dakota Sandstone does not approach steady state over much of the monitored area. A large
part of the site perched water system is in a transient state and affected by long-term changes in
water levels due to past and current activities unrelated to the disposal of materials to the TMS.
The MW-24A study indicates that naturally-occurring trace metals can be mobilized at
concentrations similar to or greater than in groundwater even without a large pH decrease,
suggesting that agitation alone, such as would occur during routine purging and sampling of low
permeability wells such as MW-24A, could result in metals mobilization. However, the lack of
steady-state conditions, in particular groundwater level changes resulting from changing
background conditions, and local increases in oxygen and/or nitrate concentrations in
groundwater, can also be expected to result in mobilization of naturally-occurring metals and
other constituents.
Based on the results of the MW-24A study EFRI has voluntarily agreed to implement a Phase 2
study to determine what geochemical and hydrogeological influences are present that may be

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affecting monitoring data collected at other wells across the Mill site. This voluntary study is in
the planning phases and will be implemented upon approval of DWMRC.

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6. SUMMARY AND CONCLUSIONS REGARDING MILL
HYDROGEOLOGY
The Mill, situated on White Mesa within the Blanding Basin physiographic province, has an
average elevation of approximately 5,600 feet above mean sea level (ft amsl), and is underlain by
unconsolidated alluvium and indurated sedimentary rocks. Indurated rocks include those exposed
within the Blanding Basin which consist primarily of sandstone and shale.
The indurated rocks are relatively flat lying with dips generally less than 3º. The alluvial
materials overlying the indurated rocks consist primarily of aeolian silts and fine-grained aeolian
sands with a thickness varying from a few feet to as much as 25 to 30 feet across the site. The
alluvium is underlain by the Dakota Sandstone and Burro Canyon Formation, and where present,
the Mancos Shale. The Dakota Sandstone and Burro Canyon Formation are sandstones having a
total thickness ranging from approximately 55 to 140 feet. Beneath the Burro Canyon Formation
lies the Morrison Formation, consisting, in descending order, of the Brushy Basin Member, the
Westwater Canyon Member, the Recapture Member, and the Salt Wash Member. The Brushy
Basin and Recapture Members of the Morrison Formation, classified as shales, are very
fine-grained and have a very low permeability. The Brushy Basin Member is primarily
composed of bentonitic mudstones, siltstones, and claystones. The Westwater Canyon and Salt
Wash Members also have a low average vertical permeability due to the presence of interbedded
shales.
Beneath the Morrison Formation lie the Summerville Formation, an argillaceous sandstone with
interbedded shales, and the Entrada Sandstone. Beneath the Entrada lies the Navajo Sandstone.
The Navajo and Entrada Sandstones constitute the primary aquifer in the vicinity of the site. The
Entrada and Navajo Sandstones are separated from the Burro Canyon Formation (and the
perched water system monitored at the site) by approximately 1,000 to 1,100 feet of materials
having a low average vertical permeability. Groundwater within the Entrada/Navajo system is
under artesian pressure in the vicinity of the site, is of generally good quality, and is used as a
secondary source of water at the site. Stratigraphic relationships beneath the site are summarized
in Figure 3.
The site and vicinity has a dry to arid continental climate, with an average annual precipitation of
approximately 13.3 inches, and an average annual lake evaporation rate of approximately 47.6
inches. Recharge to major aquifers (such as the Entrada/Navajo) occurs primarily along the
mountain fronts (for example, the Henry, Abajo, and La Sal Mountains), and along the flanks of
folds such as Comb Ridge Monocline.

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Perched groundwater beneath the site occurs in the Dakota Sandstone and Burro Canyon
Formation and is used on a limited basis to the north (upgradient) of the site because it is more
easily accessible than the Navajo/Entrada aquifer. Perched groundwater originates mainly from
precipitation and local recharge sources such as unlined reservoirs (Kirby, 2008) and is
supported within the Burro Canyon Formation by the underlying, fine-grained, and bentonitic
Brushy Basin Member, considered an aquiclude.
Water quality of the Dakota Sandstone and Burro Canyon Formation is generally poor due to
high total dissolved solids (TDS) in the range of approximately 1,100 to 7,900 milligrams per
liter (mg/L) and is used primarily for stock watering and irrigation. Nitrate and chloroform
plumes occur in site perched groundwater as shown in Figure 1B. The nitrate plume extends
from approximately 1,000 feet upgradient (north-northeast) of the TMS to beneath the TMS. The
chloroform plume is located primarily upgradient to cross-gradient (northeast to east) of the
TMS. Sources of the nitrate plume are not well-defined but the historical pond shown on Figures
1A and 1B is considered a source of nitrate and chloride to the plume. The only potentially active
source of nitrate to the plume is related to ammonium sulfate crystal handling near the
ammonium sulfate crystal tanks located southeast of TWN-2 (Figures 1A and 1B) and has been
addressed through implementation of Phase I of the nitrate CAP. Past sources of the chloroform
plume are two abandoned sanitary leach fields (located near TW4-18 and TW4-19 [Figures 1A
and 1B]) that received laboratory wastes prior to any cells within the TMS becoming operational
circa 1980. Both plumes are under remediation by pumping.
The saturated thickness of the perched groundwater zone generally increases to the north of the
site, increasing the yield of the perched zone to wells installed north of the site. The generally
low permeability of the perched zone limits well yields. Although sustainable yields of as much
as 4 gallons per minute (gpm) have been achieved in site wells penetrating higher transmissivity
zones near the unlined wildlife ponds (Figures 1A and 1B), yields are typically low (<1/2 gpm)
due to the generally low permeability of the perched zone. Even site wells that yielded as much
as 4 gpm during the first few months of pumping eventually saw yields drop to about 1 gpm or
less. As of the fourth quarter of 2021, total sustainable pumping from the 16 wells comprising
the chloroform and nitrate pumping systems was just under 6 gpm.
In addition, many of the perched monitoring wells purge dry and take several hours to more than
a day to recover sufficiently for groundwater samples to be collected. During redevelopment
(HGC, 2011b) many of the wells went dry during surging and bailing and required several
sessions on subsequent days to remove the proper volumes of water.

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As shown in Figure 5 and Appendix D, perched water flow across the site is generally (and
historically) from northeast to southwest. Perched water discharges in seeps and springs located
to the west, southwest, east, and southeast of the site (Figure 1B).
Beneath and south of the TMS, in the west central portion of the site, perched water flow is
south-southwest to west-southwest. Flow on the western margin of the mesa south of the TMS is
generally southerly, approximately parallel to the mesa rim (where the Burro Canyon Formation
is terminated by erosion). On the eastern side of the site perched water flow is also generally
southerly to southwesterly.
Perched water flow beneath and downgradient of the Mill site and TMS is influenced by perched
water discharge points Westwater Seep, located west to west-southwest of the TMS, and Ruin
Spring, located southwest of the TMS. Hydraulic gradients at the site currently range from
approximately 0.0021 ft/ft in the northeastern corner of the site (between TWN-19 and TWN-16)
to 0.098 feet per foot (ft/ft) east of cell 2 (in the vicinity of the chloroform plume, between TW4-
2 and TW4-3).
Because of relict mounding near the northern wildlife ponds, flow direction ranges from locally
westerly (west of the ponds) to locally easterly (east of the ponds). The March 2012 cessation of
water delivery to the northern ponds, which are generally upgradient of the nitrate and
chloroform plumes at the site, resulted in changing conditions that were expected to impact
constituent concentrations and migration rates within these plumes. Specifically, past recharge
from the ponds helped limit many constituent concentrations within these plumes by dilution
while the associated groundwater mounding increased hydraulic gradients and contributed to
plume migration. Since use of the northern wildlife ponds ceased in March 2012, the reduction in
recharge and decay of the associated groundwater mound have increased many constituent
concentrations within the plumes while reducing hydraulic gradients and acting to reduce rates of
plume migration. The impacts associated with cessation of water delivery to the northern ponds
were expected to (and have) propagate downgradient (south and southwest) over time.
Reduced recharge from the southern wildlife pond resulting from reduced water delivery, and the
decay of the associated (southern) perched groundwater mound, is causing changes in hydraulic
gradients in the vicinity. In particular the decay of the southern mound has resulted in more
southerly (rather than southeasterly) flow within the southernmost portion of the chloroform
plume. Continued decay of the southern mound is expected to result in eventual restoration of the
typical site southwesterly flow pattern within this portion of the plume.

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Flow onto the site occurs as underflow from areas northeast of the Mill site where perched zone
saturated thicknesses are generally greater. Any flow that does not discharge in seeps or springs
presumably exits as underflow to the southeast of Ruin Spring, along the southwest extending
lobe of White Mesa located between Ruin Spring and Corral Springs. Darcy’s Law calculations
of perched water flow to Ruin Spring and Westwater Seep yield reasonable results and suggest
that local recharge contributes to seep/spring flow.
Hydraulic testing of perched zone wells yields a hydraulic conductivity range of approximately 2
x 10-8 to 0.01 cm/s (Tables 1- 4). In general, the highest permeabilities and well yields are in the
area of the site immediately northeast and east (upgradient to cross gradient) of the TMS. A
relatively continuous, higher permeability zone associated with the chloroform plume and
consisting of poorly indurated coarser-grained materials has been inferred to exist in this portion
of the site (HGC, 2007b). Because their existence requires both coarse grain size and poor
cementation, such relatively continuous, higher permeability zones are expected to be relatively
rare at the site.
Permeabilities downgradient (southwest) of the TMS are generally low. The low permeabilities
and shallow hydraulic gradients downgradient of the TMS result in average perched groundwater
pore velocity estimates that are among the lowest on site. Furthermore, more than 41 years of
groundwater monitoring indicate no impacts to perched groundwater from TMS operation.
As discussed above, perched groundwater discharges in seeps and springs located along the mesa
margins. The relationships between seeps and springs and site geology/stratigraphy are provided
in Figure E.1 and Figure E.2. Seep and spring investigation (HGC, 2010g) and investigation of
the southwest portion of the site (HGC, 2012b) indicate the following:
1. Incorporating the seep and spring elevations in perched water elevation contour maps
produces little change with regard to perched water flow directions except in the area
west of the TMS and near Entrance Spring. West of the TMS, incorporation of Westwater
Seep creates a more westerly hydraulic gradient. Westwater Seep appears to be
downgradient of the western portion of the TMS (Figure 25); and Ruin Spring is
downgradient of the eastern portion of the TMS (Figure 25). Westwater Seep is the
closest apparent discharge point west of the TMS and Ruin Spring is the closest discharge
point south-southwest of the TMS. Including the Entrance Spring elevation on the east
side of the site creates a more easterly gradient in the perched water contours, and places
Entrance Spring more directly downgradient of the northern wildlife ponds. Seeps and
springs on the east side of the mesa are either cross-gradient of the TMS or are separated
from the TMS by a groundwater divide.
2. Ruin Spring and Westwater Seep are interpreted to occur at the contact between the
Burro Canyon Formation and the Brushy Basin Member of the Morrison Formation.

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Corral Canyon Seep, Entrance Spring, and Corral Springs are interpreted to occur at
elevations within the Burro Canyon Formation at their respective locations but above the
contact with the Brushy Basin Member. All seeps and springs (except Cottonwood Seep
which is located within the Morrison Formation near the Brushy Basin
Member/Westwater Canyon Member contact) are associated with conglomeratic portions
of the Burro Canyon Formation. Provided they are poorly indurated the more
conglomeratic portions of the Burro Canyon Formation are likely to have higher
permeabilities and the ability to transmit water more readily than finer-grained portions.
This behavior is consistent with on-site drilling and hydraulic test data that associates
higher permeability with the poorly indurated coarser-grained horizons detected east and
northeast of the TMS that are associated with the chloroform plume.
3. Cottonwood Seep is located more than 1,500 feet west of the mesa rim in an area where
the Dakota Sandstone and Burro Canyon Formation (which hosts the perched water
system) are absent due to erosion (Figures E.1 and E.2). Cottonwood Seep occurs near a
transition from slope-forming to bench-forming morphology (indicating a change in
lithology). Cottonwood Seep (and 2nd Seep located immediately to the north [Figure 6]) is
interpreted to originate from coarser-grained materials within the lower portion of the
Brushy Basin Member (or upper portion of the Westwater Canyon Member) of the
Morrison Formation. Alternatively, Cottonwood Seep may originate from coarser-grained
materials of the Westwater Canyon (sandstone) Member intertongueing with the
overlying Brushy Basin Member at the transition between the two Members. The
presence of coarser-grained materials similar to the Salt Wash (sandstone) Member
within the lower portion of the Brushy Basin member is discussed in Shawe (2005). The
intertongueing of the Westwater Canyon and Brushy Basin Members is discussed in
Craig et al. (1955) and Flesch (1974). Based on lithologic cross sections provided in
TITAN (1994), the elevation of Cottonwood Seep (5,234 ft amsl) is within 5 to 15 feet of
the elevation of the contact between the Brushy Basin Member and the underlying
Westwater Canyon Member (5,220 to 5,230 ft amsl). This is also shown in Figure 3.
Cottonwood Seep is therefore not (directly) connected to the perched water system at the
site.
4. Only Ruin Spring appears to receive a predominant and relatively consistent proportion
of its flow from perched groundwater. Ruin Spring originates from conglomeratic Burro
Canyon Formation sandstone where it contacts the underlying Brushy Basin Member, at
an elevation above the alluvium in the associated drainage. Westwater Seep, which also
originates at the contact between the Burro Canyon Formation and the Brushy Basin
Member, likely receives a significant contribution from perched water. All seeps and
springs other than Ruin Spring (and 2nd Seep just north of Cottonwood Seep) are located
within alluvium occupying the basal portions of small drainages and canyons. The
relative contribution of flow to these features from bedrock and from alluvium is
indeterminate.
5. All seeps and springs are reported to have enhanced flow during wet periods. For seeps
and springs associated with alluvium, this behavior is consistent with an alluvial
contribution to flow. Enhanced flow during wet periods at Ruin Spring, which originates
from bedrock above the level of the alluvium, likely results from direct recharge of Burro

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Canyon Formation and Dakota Sandstone exposed near the mesa margin in the vicinity of
Ruin Spring. This recharge would be expected to temporarily increase the flow at Ruin
Spring (as well as other seeps and springs where associated bedrock is directly recharged)
after precipitation events. As discussed previously, local recharge is consistent with
Darcy’s law calculations of perched water flow to Ruin Spring and Westwater Seep.
6. The assumption that the seep or spring elevation is representative of the perched water
elevation is likely to be correct only where the feature receives most or all of its flow
from perched water and where the supply is relatively continuous (for example at Ruin
Spring). The perched water elevation at the location of a seep or spring that receives a
significant proportion of water from a source other than perched water may be different
from the elevation of the seep or spring. The elevations of seeps that are dry for at least
part of the year will not be representative of the perched water elevation when dry. Some
uncertainty therefore results from including these seeps and springs in the contouring of
perched water levels. However, even if such springs are sometimes dry, the presence of
cottonwoods suggests that perched groundwater is close to the surface at these locations.

The rate of perched water flow in the southwest area of the site (downgradient of the TMS) is
small and contributions from local recharge are needed to explain many areas of higher saturated
thickness affected by discharge points such as Westwater Seep and Ruin Spring that are
downgradient of areas of low saturated thickness (HGC, 2012b). The presence of local recharge
is expected to affect the water quality of seeps and springs and has the potential to dilute any
dissolved constituents that may migrate from upgradient areas.
As discussed in HGC (2012c), samples of selected archived drill core and drill cuttings were
analyzed visually and quantitatively by a contract analytical laboratory. Table 13 and Figure 32
summarize the occurrence of pyrite in site borings based on lithologic logs and laboratory
analyses. The results verify the site-wide, apparently ubiquitous existence of pyrite in the
perched zone at the site. The existence of pyrite is confirmed at locations upgradient, cross-
gradient, and downgradient of the Mill site and TMS. The results are consistent with Shawe’s
(1976) description of the Dakota Sandstone and Burro Canyon Formations as “altered-facies”
rocks within which pyrite formed as a result of invasion by pore waters originating from
compaction of the overlying Mancos Shale.
A large portion of the perched water system at the site is in a transient state, manifested in long-
term changes in saturated thicknesses and rates of groundwater flow. This condition is expected
to result in trends in pH and concentrations of many dissolved constituents that are unrelated to
site operations. Changes in saturated thicknesses and rates of groundwater flow can result in
changes in concentrations of dissolved constituents (or pH) for many reasons. For example, as
discussed in HGC (2012c), groundwater rising into a vadose zone having a different chemistry

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than the saturated zone can result in changes in pH and groundwater constituent concentrations.
If the rise in groundwater represents a long-term trend, long-term changes in groundwater
constituent concentrations (or pH) may result.
Under conditions where vadose zone chemistry is not markedly different from saturated zone
chemistry, changing groundwater flow rates may result in changing constituent concentrations
due to changes in dilution. For example, relatively constant flux of a particular solute into the
groundwater zone, resulting in a relatively constant groundwater concentration under conditions
of steady groundwater flow, will likely result in changing concentrations should groundwater
flow become unsteady. If the change in flow rate is in one direction over a long period of time, a
long-term trend in the solute concentration is expected to result. Examples include oxygen
dissolved in recharge or a constituent present in vadose zone materials overlying perched
groundwater that dissolves in recharge and leaches into perched water at a steady rate. An
increase in perched flow may cause an increase in dilution and a reduction in constituent
concentration and vice-versa. For example, the decrease in dilution related to cessation of water
delivery to the northern wildlife ponds has caused increases in dissolved constituent
concentrations within the chloroform plume and, to a lesser extent, the nitrate plume.
Furthermore the lined cells within the TMS are expected to act as barriers to natural recharge and
exchange of gas with the atmosphere; their mere presence may thus result in changes in perched
water chemistry. Any such changes are likely to be relatively slow and in one direction,
potentially yielding long term trends in parameter values.
The perched groundwater chemistry at the Mill is also expected to be impacted by the following
factors:
1. The relatively low permeability of the perched zone. This condition increases
groundwater residence times and the time available for groundwater to react with the
formation.
2. The location of the perched system between two shales, the underlying Brushy Basin
Member of the Morrison Formation and the overlying Mancos Shale. Both are potential
sources of numerous dissolved constituents. The potential for natural contamination from
the Mancos Shale is discussed in USDOE (2011).
3. The rate of interaction between the Mancos and Brushy Basin Member shales and the
perched water. Interaction with the Mancos Shale at any particular location will depend
on the presence, thickness, and composition of the Mancos, the rate of recharge through
the Mancos into the perched zone, and the saturated thickness and rate of groundwater
flow in the perched zone. Interaction with the Brushy Basin Member at any particular
location will depend on the composition of the Brushy Basin, and the saturated thickness
and rate of flow in the perched zone. Oxygen introduced into site monitoring wells may

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also react with the Brushy Basin and affect the chemistry of perched groundwater in
contact with the Brushy Basin.
4. The rate of oxygen introduction into the perched zone via recharge or via site
groundwater monitoring wells. Introduced oxygen is available to oxidize constituents
such as pyrite, which impacts the local groundwater chemistry near each recharge source
and near each well by releasing acid and sulfate. The resulting increased acidity can also
destabilize various mineral phases in the aquifer matrix. The degree of impact on
groundwater chemistry will depend on the amount of pyrite, the rate of oxygen transfer,
the neutralization capacity and saturated thickness of the perched zone, and the rate of
groundwater flow.
5. Elements other than iron and sulfur as contaminants in pyrite. Pyrite reacting with oxygen
introduced into the formation will release these elements, potentially altering both the
vadose zone and the groundwater chemistry. The likelihood of pyrite having significant
contaminants (such as selenium) is enhanced considering its origin from fluids expelled
from the Mancos. As discussed in EFRI (2021b), bottle-roll tests using pyrite-bearing
core from the formation hosting perched groundwater at the site yielded bottle-roll
solutions initially consisting of laboratory-grade DI water generating as much as 74 µg/L
beryllium; 118 µg/L cadmium; 79 µg/L cobalt; 959 µg/L copper; 4,120 µg/L manganese;
278 µg/L nickel; 303 µg/L selenium; 2.3 µg/L thallium; 6,700 µg/L uranium; and 1,680
µg/L zinc; as well as elevated concentrations other constituents.

Changes in perched zone constituent concentrations and pH are therefore expected to result from
the introduction of oxygen into the subsurface, the oxidation of pyrite and other constituents,
changes in recharge rates, and past and current recharge passing through the Mancos Shale.
Pyrite may also be oxidized by nitrate, impacting wells affected by the nitrate plume (which
originates approximately 1,000 feet upgradient of the TMS).
Decreasing trends in pH accompanied by increasing sulfate concentrations in MW-series wells
that were previously OOC for pH were determined to result from oxidation of pyrite based on
screening-level calculations and geochemical modeling presented in HGC (2012c). The
calculations also indicated that pyrite existed in sufficient quantity to maintain these trends
provided sufficient oxygen was available. In addition, pH decreases at wells impacted by the
nitrate plume could result from nitrate degradation of pyrite by the reaction mechanism that
produces, rather than consume, acid as discussed in Section 4.4.2. Furthermore, although the pH
decrease was an apparently site-wide phenomenon, since about 2016, pH in nearly all MW-series
wells has stabilized and has begun to increase. As discussed in EFRI (2022a) and EFRI (2022d),
because TMS solutions have very low pH, the post-2016 increases indicate that TMS solutions
cannot be impacting groundwater.

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6.1 Perched Water Pore Velocities in the Nitrate Plume Area
Perched groundwater pore velocities and travel times calculated within the nitrate plume along
Path 1 (Figure 27) yield an estimated average pore velocity of approximately 11 ft/yr and a travel
time of approximately 176 years, based on a fourth quarter, 2021 hydraulic gradient of 0.0165
ft/ft.
Historic hydraulic gradients within the area of the nitrate plume were likely much larger than the
current hydraulic gradient of 0.0165 ft/ft during the time prior to Mill construction when the
historical pond was active (Figure 1B). Based on historic water levels in the vicinities of MW-30
and MW-31, located along the downgradient margin of cell 2 (Appendix D), and at the
downgradient margin of the nitrate plume, an historic hydraulic gradient is estimated as
approximately 0.048 ft/ft. This is more than four times the overall average site hydraulic gradient
of approximately 0.011 ft/ft (calculated between TWN-19 and Ruin Spring).
Using the estimated historic hydraulic gradient of 0.048 ft/ft, the estimated historic pore velocity
downgradient of the historical pond is approximately 32 ft/yr, implying that nitrate originating
from the historical pond could have migrated to the downgradient edge of cell 2 within 69 years.
Assuming the historical pond was active by 1920, that nitrate was conservative, and ignoring
hydrodynamic dispersion, nitrate originating from the historical pond could have reached the
vicinities of MW-30 and MW-31 by 1989.
6.2 Perched Water Pore Velocities in the Vicinity of the Chloroform Plume
Perched groundwater pore velocities and travel times in the vicinity of the chloroform plume
along Paths 2A and 2B (Figure 27) were calculated based on fourth quarter, 2021 hydraulic
gradients of 0.034 ft/ft and 0.057 ft/ft, respectively. The estimated average pore velocity along
Path 2A is approximately 63 ft/yr, implying that approximately 17 years would be required to
traverse Path 2A. The estimated average pore velocity along Path 2B is approximately 38 ft/yr,
implying that approximately 28 years would be required to traverse Path 2B.
Historic hydraulic gradients within the northern (upgradient) areas of the eastern portion of the
chloroform plume (prior to about 1990) were likely larger than current hydraulic gradients and
contributed to relatively rapid movement of chloroform from the abandoned scale house leach
field (located immediately north of TW4-18) to MW-4 where chloroform was detected in 1999.
Based on historic water levels (Appendix D) the hydraulic gradient between the abandoned scale
house leach field and MW-4 is estimated as approximately 0.048 ft/ft in 1990 and approximately
0.029 ft/ft in 1999, averaging 0.038 ft/ft. This is more than three times the overall average site

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hydraulic gradient of approximately 0.011 ft/ft (calculated between TWN-19 and Ruin Spring),
but is within the range of hydraulic gradients occurring at present within and adjacent to the
chloroform plume, and is similar to the current hydraulic gradient of approximately 0.041 ft/ft
just east the plume, between non-pumping wells TW4-36 and TW4-27.
The estimated historic hydraulic gradient implies an average pore velocity prior to 1999 of
approximately 84 ft/yr, sufficient for chloroform to have migrated from the abandoned scale
house leach field to MW-4 between 1978 and 1999. This calculation implies that chloroform
could have migrated nearly to TW4-4 by 1999.
6.3 Hydrogeology and Perched Water Pore Velocities in the Southwest
Area
Investigation of the southwest area of the site, including seeps and springs (HGC, 2012b),
indicates that permeabilities in the southwest portion of the site are on average lower than
estimated prior to 2010 (as for example in HGC, 2009), and that perched water discharges to
Westwater Seep and Ruin Spring, but there is no evidence for a direct hydraulic connection
between the perched water zone and Cottonwood Seep. The hydraulic test and water level data
also demonstrate that the perched zone southwest of cell 4B is inadequate as a primary supply to
Cottonwood Seep by several orders of magnitude and that that the primary source of Cottonwood
Seep lies elsewhere. However, a hypothetical connection between the perched zone near
piezometer DR-8 and Cottonwood Seep is postulated for the purposes of calculating perched
water travel times and to allow for the possibility that an as yet unidentified connection may
exist.
Important results of the southwest area investigation are:
1. The Brushy Basin Member erosional paleosurface in the southwest area of the Mill site is
dominated by a paleoridge extending from beneath cell 4B to abandoned boring DR-18
(Figure 8). The paleoridge is flanked to the west by a north-south trending paleovalley
oriented roughly parallel to the western mesa rim (Figure 8).
2. The southwest area of the Mill site is characterized by generally low saturated
thicknesses, low permeabilities, and relatively shallow hydraulic gradients. This is
illustrated in Table 1 and Figure 14. Hydraulic gradients in the southwest portion of the
site are typically close to 0.1 ft/ft, but are less than approximately 0.005 ft/ft
west/southwest of cell 4B, between cell 4B and DR-8.
3. The paleotopography of the Brushy Basin Member erosional surface has a greater
influence on perched water flow in the southwest portion of the site than other areas
because of the low saturated thicknesses and dry areas associated with the paleoridge
extending south-southwest from the TMS (Figures 8, 14, 18, and 19).

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4. The low transmissivities implied by the low permeabilities and low saturated thicknesses
combined with the shallow hydraulic gradients imply low rates of perched water flow in
the southwest portion of the site. Calculated average pore velocities along Pathlines 3, 5,
and 6 (Figure 27) from the TMS to known discharge points Westwater Seep and Ruin
Spring range from 0.60 ft/yr to 0.91 ft/yr, and travel times from approximately 2,895 to
19,665 years based on fourth quarter, 2021 water level data. If vadose zone travel times
from the base of the individual cells to the perched water are included, the range of
calculated travel times is approximately 3,175 to 19,995 years.
5. The estimated travel time from the TMS to the vicinity of DR-8 (Path 4) is approximately
15,865 years based on fourth quarter, 2021 water level data and a calculated pore velocity
of 0.26 ft/yr. Including the vadose travel time of approximately 329 years yields a total
travel time of approximately 16,195 years. Assuming a hypothetical pathway to
Cottonwood Seep, the time to travel along Path 4 and thence along the potential pathway
from the edge of Path 4 to Cottonwood Seep (which adds approximately 2,150 horizontal
feet) is expected to be significantly greater than 16,195 years.
6. Brushy Basin Member paleotopography influences the locations of Westwater Seep and
Ruin Spring; both are located in paleovalleys within the Brushy Basin Member
paleosurface (Figure 8).
7. Local recharge is needed to explain areas of relatively large saturated thickness that
supply Westwater Seep and Ruin Spring, because lateral flow into these areas from
upgradient low saturated thickness portions of the perched zone is inadequate. The
calculated perched zone recharge rate in the approximate 175 acre area southwest of
Westwater Seep (near DR-2 [abandoned] and DR-5) is approximately 0.001 in/yr.
8. The perched water system in the southwestern portion of the site is inadequate as the
primary supply to Cottonwood Seep by several orders of magnitude. Therefore the
primary source(s) of Cottonwood Seep must lie elsewhere.
6.4 Fate of Chloroform and Nitrate
Natural attenuation of nitrate and chloroform in the perched water is expected to result from
physical processes that include dilution by recharge and hydrodynamic dispersion. Volatilization
is another physical process that is expected to lower chloroform concentrations in perched water.
Mass reduction processes expected to lower both nitrate and chloroform concentrations include
chemical and biologically-mediated processes. These processes include reduction of nitrate by
pyrite, and anaerobic reductive dechlorination of chloroform.
Both nitrate and chloroform plumes are under remediation by pumping. Pumping acts to reduce
nitrate and chloroform mass as rapidly as is practical, allowing natural attenuation to be more
effective.

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The nearest potential discharge points for nitrate originating from the nitrate plume are
Westwater Seep and Ruin Spring, both located downgradient of the TMS at the site. The nearest
potential discharge point for chloroform is Ruin Spring. Corral Springs, located cross-gradient of
the TMS, appears to be positioned too far east for any potential future impacts by chloroform.
Calculations of perched groundwater flow rates indicate that thousands of years will be required
for perched groundwater at the downgradient margins of the TMS to reach a discharge point.
Because both chloroform and nitrate plumes are more distant from discharge points than the
TMS, even more time would be required for chloroform or nitrate to reach a discharge point.
Since both plumes are expected to naturally attenuate within less than 200 years (through
physical, chemical, and/or biological processes), even in the absence of direct mass removal by
pumping, there is more than sufficient time for any residual chloroform or nitrate within the
respective plumes to degrade before reaching a discharge point. In addition, as discussed in HGC
(2018e), numerical flow and transport modeling using conservatively large hydraulic
conductivities and hydraulic gradients, and conservatively small dispersivities, demonstrates that
natural attenuation, even in the absence of nitrate reduction by pyrite and mass removal by
pumping, would reduce all concentrations within the nitrate plume to less than the 10 mg/L
GCAL before reaching a property boundary.

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7. PROPOSED CELLS 5A AND 5B
Cells 5A and 5B are proposed to be located as shown on Figure 33. Based on analyses presented
in HGC (2018d); HGC (2018e); and HGC (2019a), seven new perched groundwater monitoring
wells MW-42 though MW-48; and one new perched groundwater piezometer (DR-26); are
proposed to be located as shown on Figure 33. As final approval of the proposed design is
pending, the locations of these proposed installations are subject to change.
Details of the hydrogeology of the perched groundwater zone beneath proposed cells 5A and 5B,
and the rationale for selection of the number and locations of monitoring installations, are
provided in Appendix F. In addition to HGC (2018d), HGC (2018e) and HGC (2019a),
conclusions presented in Appendix F are based on HGC (2001a); HGC (2001b); HGC (2005);
and Knight-Piésold (1998).

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9. LIMITATIONS STATEMENT
The opinions and recommendations presented in this report are based upon the scope of services
and information obtained through the performance of the services, as agreed upon by HGC and
the party for whom this report was originally prepared. Results of any investigations, tests, or
findings presented in this report apply solely to conditions existing at the time HGC’s
investigative work was performed and are inherently based on and limited to the available data
and the extent of the investigation activities. No representation, warranty, or guarantee, express
or implied, is intended or given. HGC makes no representation as to the accuracy or
completeness of any information provided by other parties not under contract to HGC to the
extent that HGC relied upon that information. This report is expressly for the sole and exclusive
use of the party for whom this report was originally prepared and for the particular purpose that
it was intended. Reuse of this report, or any portion thereof, for other than its intended purpose,
or if modified, or if used by third parties, shall be at the sole risk of the user.

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TABLES
TABLE 1
Results of Slug test Analyses Using KGS and Bouwer-Rice Solutions
Bouwer-Rice Bouwer-Rice
Test Saturated
Thickness
K
(cm/s)
Ss
(1/ft)
K
(cm/s)
K
(cm/s)
Ss
(1/ft)
K
(cm/s)
TWN-1 54 1.70E-04 2.22E-03 NI 1.97E-04 1.25E-03 1.36E-04
TWN-2 74 1.49E-05 3.20E-04 2.25E-05 2.04E-05 1.16E-04 2.73E-05
TWN-3 60 8.56E-06 8.73E-06 8.97E-06 7.75E-06 1.53E-05 8.89E-06
TWN-4 85 1.76E-03 3.43E-04 2.79E-05 1.25E-03 1.84E-06 NI
TWN-5 77 4.88E-04 3.88E-07 4.06E-04 4.88E-04 3.88E-07 3.70E-04
TWN-6 79 1.74E-04 2.22E-03 NI 3.50E-04 2.22E-12 3.36E-04
TWN-7 11 3.57E-07 2.22E-03 4.59E-07 3.57E-07 2.21E-03 NI
TWN-8 80 1.51E-04 3.66E-04 7.55E-05 4.73E-04 1.41E-06 2.48E-04
TWN-9 29 2.99E-05 6.92E-03 2.86E-05 6.02E-05 5.59E-03 7.93E-05
TWN-10 20 3.83E-05 0.1 2.31E-05 8.71E-05 8.12E-03 1.10E-04
TWN-11 68 1.18E-04 1.08E-05 9.83E-05 9.34E-05 7.18E-05 9.78E-05
TWN-12 67 8.05E-05 4.65E-05 7.69E-05 1.28E-04 1.27E-07 7.39E-05
TWN-13 68 2.62E-06 0.1 4.77E-06 2.09E-06 0.1 6.93E-06
TWN-14 57 3.61E-06 6.39E-03 2.74E-06 3.98E-06 3.17E-03 7.93E-06
TWN-15 58 4.75E-05 1.04E-03 2.61E-05 5.86E-05 3.49E-04 6.42E-05
TWN-16 41 0.0142 8.02E-04 6.47E-03 NI NI NI
TWN-17 69 3.73E-06 0.033 6.18E-06 1.41E-06 0.061 1.96E-06
TWN-18 83 2.27E-03 2.44E-06 1.14E-03 2.67E-03 2.22E-12 NI
TWN-19 50 2.69E-05 2.49E-03 1.81E-05 3.83E-05 3.34E-03 NI
TWN-20 19 1.06E-05 5.74E-04 1.07E-05 1.65E-05 2.10E-04 2.22E-05
TWN-21 28 2.80E-05 9.82E-04 3.00E-05 2.97E-05 1.39E-03 4.59E-05
MW-03 (mlt) 5.2 4.00E-07 1.92E-02 1.50E-05 -- -- --
MW-05 (lt)3.90E-06 4.30E-06
MW-05 (et)2.40E-05 1.80E-05
MW-17 18 2.60E-05 1.71E-04 2.70E-05 2.20E-05 -- 3.00E-05
MW-18 58 2.90E-04 4.60E-07 2.40E-04 3.20E-04 -- 2.50E-04
MW-19 80 1.70E-05 1.44E-06 1.30E-05 1.20E-05 -- 1.50E-05
MW-19, confined 47 1.60E-05 3.24E-06 1.20E-05 -- -- --
MW-20 (mlt)9.30E-06 --
MW-20 (mlt)5.90E-06 2.50E-06
MW-22 7.90E-06 --
MW-22 4.40E-06 3.40E-06
MW-23 12 3.20E-08 0.1 1.60E-06 NI NI NI
MW-23b 12 2.30E-07 2.30E-03 2.50E-07 NI NI 2.00E-07
MW-24 3.4 4.16E-05 5.20E-03 3.15E-05 3.03E-05 0.0152 3.03E-05
MW-24A 9 1.41E-05 1.10E-02 1.85E-05 1.97E-05 4.88E-03 1.88E-05
MW-25 33 1.10E-04 3.00E-04 7.40E-05 1.70E-04 2.00E-04 1.00E-04
MW-27 36 8.20E-05 5.30E-04 3.60E-05 1.40E-04 8.70E-05 3.10E-05
MW-28 23 1.70E-06 0.02 1.70E-06 1.70E-06 0.02 2.00E-06
MW-29 18 1.10E-04 1.90E-04 9.30E-05 1.30E-04 2.10E-04 1.00E-04
MW-30 24 1.00E-04 2.90E-04 6.40E-05 1.10E-04 1.40E-04 5.10E-05
MW-31 53 7.10E-05 2.50E-05 6.90E-05 7.40E-05 7.20E-06 6.90E-05
MW-32 46 3.00E-05 8.80E-05 2.60E-05 2.80E-05 2.50E-04 3.00E-05
MW-35 12 3.48E-04 1.95E-05 2.18E-04 2.59E-04 1.78E-05 1.65E-04
MW-36 6.2 4.51E-04 4.29E-04 NA 7.73E-04 2.66E-04 6.52E-04
MW-36 (lt)6.2 NA NA 1.84E-04 NA NA NA
MW-36 (et)6.2 NA NA 5.07E-04 NA NA NA
MW-37 2.9 1.28E-05 2.22E-12 1.21E-05 NA NA NA
MW-38 3.0 6.84E-05 0.022 5.90E-05 5.13E-05 0.015 6.86E-05
MW-39 33 1.76E-05 8.07E-04 2.43E-05 1.43E-05 3.80E-03 2.48E-05
MW-40 38 1.26E-04 3.36E-04 1.23E-04 1.26E-04 3.36E-04 2.08E-04
MW-40 (lt)38 NA NA 4.18E-05 NA NA NA
TW4-4 (et) 22 NA NA 1.26E-03 NA NA NA
TW4-4 (lt) 22 1.66E-03 6.21E-05 2.89E-04 1.63E-03 3.01E-04 7.91E-04
TW4-6 24 1.15E-05 3.67E-05 1.00E-05 1.19E-05 1.49E-04 1.32E-05
TW4-20 43 5.90E-05 1.60E-05 4.20E-05 7.00E-05 1.20E-05 5.30E-05
TW4-21 63 1.90E-04 1.10E-04 3.20E-05 1.90E-04 3.20E-05 9.40E-06
TW4-22 55 1.30E-04 6.80E-06 1.10E-04 1.30E-04 4.50E-06 1.10E-04
TW4-23 43 3.80E-05 7.40E-03 2.90E-05 3.40E-01 6.40E-04 7.90E-05
TW4-24 53 1.60E-04 1.10E-03 1.00E-04 1.20E-04 1.70E-03 5.20E-05
TW4-25 89 5.80E-05 0.001 3.70E-05 7.40E-05 1.10E-03 5.00E-05
TW4-26 18 2.40E-05 3.23E-04 2.16E-05 2.28E-05 3.13E-04 2.55E-05
TW4-27 (uncorrected) NA NA NA 2.13E-06 1.51E-03 1.59E-06
TW4-27 (100% correction) 7.01E-07 2.22E-03 1.99E-06 NA NA NA
TW4-27(60% correction) 1.35E-06 1.27E-03 1.15E-06 NA NA NA
TW4-28 67.9 3.52E-04 1.22E-06 3.92E-04 3.29E-04 7.49E-06 4.07E-04
TW4-29 17.7 4.24E-05 1.19E-03 5.24E-05 4.52E-05 9.62E-04 5.66E-05
TW4-29 (lt) 17.7 NA NA 2.00E-05 NA NA 3.80E-05
TW4-30 9.6 1.44E-04 1.00E-02 6.22E-05 1.34E-04 1.00E-02 1.38E-04
TW4-30 (et) 9.6 NA NA 1.63E-04 NA NA 2.91E-04
TW4-30 (lt)9.6 NA NA 1.12E-05 NA NA 1.41E-05
TW4-31 18.1 4.18E-05 2.54E-05 3.87E-05 3.24E-05 9.65E-05 4.01E-05
TW4-32 64.8 9.53E-05 1.15E-04 NA 5.34E-05 7.97E-04 5.86E-05
TW4-32(et) 64.8 NA NA 1.09E-04 NA NA 1.34E-04
TW4-32(lt) 64.8 NA NA 2.51E-05 NA NA 1.17E-05
TW4-33 13.1 5.51E-05 3.73E-04 5.78E-05 5.25E-05 5.32E-04 5.76E-05
TW4-34 25.2 9.98E-05 1.13E-03 1.54E-04 9.39E-05 1.54E-03 1.25E-04
TW4-34 (lt) 25.2 NA NA 1.17E-04 NA NA NA
TW4-35 8.8 6.27E-05 1.49E-03 5.72E-05 5.72E-05 1.69E-03 6.42E-05
TW4-36 36.7 3.23E-06 1.07E-03 6.39E-06 1.82E-06 2.83E-03 4.79E-06
TW4-37 51.6 1.43E-04 2.14E-04 2.17E-04 1.93E-04 8.60E-05 2.33E-04
TW4-38 6.37E-05 1.15E-04 NA 4.76E-05 2.81E-05 NA
TW4-38 (mlt)NA NA 7.16E-05 NA NA 5.54E-05
TW4-38 (lt)NA NA 5.68E-05 NA NA 3.76E-05
TW4-39 5.27E-05 2.03E-04 NA 6.15E-05 1.70E-04 NA
TW4-39 (mlt)NA NA 7.21E-05 NA NA 8.41E-05
TW4-39 (lt)NA NA 2.85E-05 NA NA 3.17E-05
TW4-40 19.3 9.81E-03 3.96E-04 8.54E-03 9.81E-03 3.96E-04 6.48E-03
TW4-41 17.9 2.69E-03 2.22E-03 3.03E-03 2.69E-03 2.22E-03 5.40E-03
TW4-42 20.5 2.43E-05 2.22E-03 2.92E-05 3.25E-05 1.55E-03 4.92E-05
TW4-43 19.4 4.37E-05 5.44E-04 5.76E-05 5.84E-05 2.43E-04 6.40E-05
DR-5 12.3 2.95E-05 4.21E-05 3.80E-05 2.86E-05 2.65E-03 3.76E-05
DR-8, Oct 2012 7.8 2.46E-08 1.00E-02 3.56E-07 4.46E-08 1.00E-02 4.45E-07
DR-8, Oct 2011 7.7 3.40E-08 0.01 NA 1.07E-07 0.0011 NA
DR-9 24.5 4.49E-04 4.30E-06 3.41E-04 4.73E-04 1.21E-05 4.73E-04
DR-10 3 2.92E-06 6.54E-03 5.56E-06 9.71E-06 8.41E-04 9.71E-06
DR-11 8.9 8.88E-06 8.88E-04 1.54E-05 5.83E-06 2.22E-03 1.11E-05
DR-13 11.2 5.90E-06 7.33E-05 5.38E-06 4.93E-06 1.57E-04 1.49E-06
DR-13(et) 11.2 NA NA NA NA NA 6.81E-06
DR-14 18.8 1.26E-05 7.34E-05 1.66E-05 7.78E-06 4.84E-04 6.18E-06
DR-14(et) 18.8 NA NA NA NA NA 1.23E-05
DR-17 6.5 1.24E-05 1.53E-04 1.43E-05 3.17E-06 5.00E-03 2.19E-06
DR-17(et) 6.5 NA NA NA NA NA 8.35E-06
DR-19 3.5 3.29E-05 2.54E-03 3.78E-05 3.39E-05 1.86E-03 4.08E-05
DR-20 17.9 2.14E-06 1.91E-05 2.69E-06 1.43E-06 1.90E-05 1.89E-06
DR-21 13.5 3.29E-05 7.17E-06 3.60E-05 2.21E-05 1.87E-04 3.49E-05
DR-23 7.5 1.96E-05 3.85E-04 2.35E-05 7.49E-06 5.00E-03 4.51E-06
DR-23(et) 7.5 NA NA NA NA NA 2.16E-05
DR-24 17.4 1.64E-05 7.49E-05 1.43E-05 1.64E-05 7.49E-05 8.23E-06
DR-24(et) 17.4 NA NA NA NA NA 1.97E-05
Notes:
Bouwer-Rice = Unconfined Bouwer-Rice solution method in Aqtesolv™ unless otherwise noted
cm/s = centimeters per second
ft = feet
K = hydraulic conductivity
KGS = Unconfined KGS solution method in Aqtesolv™ unless otherwise noted
Ss= specific storage
NI= Not Interpretable .
et= early time data
mlt=middle to late time data
lt=late time data
NA=not applicable
Automatically Logged Data
12 -- --
51 1.00E-06 2.00E-03
Hand Collected Data
KGS KGS
10 3.50E-06 4.40E-03
57.97
56.3
9.00E-07 --
3.20E-06 --
-- --
9
H:\718000\hydrpt2022\tables\T1_2_3_6_Hydraulic_props_4Q21_rev.xls: T1-KGS and B-R slug test K data
TABLE 2
Results of Recovery and Slug Test Analyses Using Moench Solution
Hand Data
Well ID Interpretation
Method Type
Hydraulic
Conductivity
(cm/sec)
Storativity
Saturated
Thickness
(feet)
Skin Hydraulic Conductivity
(cm/sec)
WHIP pump/recovery 7.70E-07 0.0082 20 none 7.70E-07
AQTESOLV
(Moench, Leaky)pump/recovery 7.70E-07 0.0082 20 none 7.70E-07
AQTESOLV
(Moench, Unconfined)pump/recovery 8.90E-07 0.01 40 none --
MW-03 WHIP slug 4.30E-05 0.01 5.2 none --
MW-05 WHIP slug 1.10E-05 0.1 10 none --
MW-17 WHIP slug 2.90E-05 0.01 18 none --
WHIP slug 4.40E-04 2.20E-05 45 none --
WHIP slug 5.30E-04 0.02 45 6.54 --
WHIP slug 7.10E-06 0.032 47 none --
WHIP slug 1.70E-05 0.027 47 2.24 --
AQTESOLV
(Moench, Leaky)slug 1.70E-05 0.027 47 2.24 --
MW-20 WHIP slug 8.20E-06 0.02 12 none --
MW-22 WHIP slug 4.20E-06 0.014 51 none --
Notes:
cm/sec = Centimeters per second
WHIP analyses via modfied Moench Leaky Solution
MW-01
MW-19
Automatically-Logged Data
MW-18
H:\718000\hydrpt2022\tables\T1_2_3_6_Hydraulic_props_4Q21.xls: T2-Moench and WHIP data 4/7/2022
TABLE 3
Estimated Perched Zone Hydraulic Properties Based on
Analysis of Observation Wells Near MW-4 and TW4-19 During Long Term Pumping of MW-4 and TW4-19
Observation
Well
Theis Solution
(Confined or
Unconfined)
Transmissivity
(ft2/day)
Storage
Coefficient
Water Bearing
Zone Thickness
(feet)
Average Hydraulic
Conductivity
(ft/day)
Average Hydraulic
Conductivity
(cm/sec)
Unconfined 8.9 0.023 39 0.23 8.20E-05
Confined 8.4 0.023 24 0.35 1.30E-04
Unconfined 4.6 0.0065 39 0.12 4.30E-05
Confined 3.8 0.0063 24 0.16 5.70E-05
Unconfined 4.7 0.011 39 0.12 4.30E-05
Confined 3.3 0.011 24 0.14 5.00E-05
Unconfined 4.5 0.010 39 0.12 4.30E-05
Confined 3.9 0.010 24 0.16 5.70E-05
Unconfined 5.8 0.019 39 0.15 5.40E-05
Confined 3.5 0.019 24 0.15 5.40E-05
Unconfined 12.4 0.0029 39 0.32 1.10E-04
Confined 9.1 0.0031 24 0.38 1.40E-04
Unconfined 89 0.0043 67 1.3 4.60E-04
Confined 87 0.0043 31 2.8 1.00E-03
Unconfined 72 0.0043 67 1.1 3.90E-04
Confined 71 0.0043 31 2.3 8.20E-04
Unconfined 48 0.0077 67 0.72 2.60E-04
Confined 46 0.0076 31 1.5 5.40E-04
Unconfined 15 0.0037 67 0.22 7.90E-05
Confined 12 0.0037 31 0.39 1.40E-04
Unconfined 19 0.0036 67 0.28 1.00E-04
Confined 18 0.0035 31 0.58 2.10E-04
Unconfined 76 0.0046 67 1.1 3.90E-04
Confined 74 0.0046 31 2.4 8.60E-04
Unconfined 44 0.12 67 0.66 2.40E-04
Confined 39 0.12 31 1.3 4.60E-04
Notes:
cm/sec = Centimeters per second
ft/day = Feet per day
ft2/day = Feet squared per day
TW4-16
TW4-18
TW4-19
TW4-5
TW4-9
TW4-10
TW4-15 (MW-26)
MW-4A
(early time)
TW4-1
TW4-2
TW4-7
TW4-8
MW-4A
H:\718000\hydrpt2022\tables\T1_2_3_6_Hydraulic_props_4Q21.xls: T3-Pump Test Obs Wells Page 1 of 1 4/7/2022
TABLE 4
Summary of Hydraulic Properties
White Mesa Uranium Mill
from TITAN (1994)
Soils
6 Laboratory Test 9 D&M 1.20E+01 1.20E-05
7 Laboratory Test 4.5 D&M 1.00E+01 1.00E-05
10 Laboratory Test 4 D&M 1.20E+01 1.20E-05
12 Laboratory Test 9 D&M 1.40E+02 1.40E-04
16 Laboratory Test 4.5 D&M 2.20E+01 2.10E-05
17 Laboratory Test 4.5 D&M 9.30E+01 9.00E-05
19 Laboratory Test 4 D&M 7.00E+01 6.80E-05
22 Laboratory Test 4 D&M 3.90E+00 3.80E-06
Geometric Mean 2.45E+01 2.37E-05
Dakota Sandstone
No. 3 Injection Test 28-33 D&M (1) 5.68E+02 5.49E-04
No. 3 Injection Test 33-42.5 D&M 2.80E+00 2.71E-06
No. 12 Injection Test 16-22.5 D&M 5.10E+00 4.93E-06
No. 12 Injection Test 22.5-37.5 D&M 7.92E+01 7.66E-05
No. 19 Injection Test 26-37.5 D&M 7.00E+00 6.77E-06
No. 19 Injection Test 37.5-52.5 D&M 9.44E+02 9.12E-04
Geometric Mean 4.03E+01 3.89E-05
Burro Canyon Formation
No. 3 Injection Test 42.5-52.5 D&M 5.80E+00 5.61E-06
No. 3 Injection Test 52.5-63 D&M 1.62E+01 1.57E-05
No. 3 Injection Test 63-72.5 D&M 5.30E+00 5.13E-06
No. 3 Injection Test 72.5-92.5 D&M 3.20E+00 3.09E-06
No. 3 Injection Test 92.5-107.5 D&M 4.90E+00 4.74E-06
No. 3 Injection Test 122.5-142 D&M 6.00E-01 5.80E-07
No. 9 Injection Test 27.5-42.5 D&M 2.70E+00 2.61E-06
No. 9 Injection Test 42.5-59 D&M 2.00E+00 1.93E-06
No. 9 Injection Test 59-82.5 D&M 7.00E-01 6.77E-07
No. 9 Injection Test 82.5-107.5 D&M 1.10E+00 1.06E-06
No. 9 Injection Test 107.5-132 D&M 3.00E-01 2.90E-07
No. 12 Injection Test 37.5-57.5 D&M 9.01E-01 8.70E-07
No. 12 Injection Test 57.5-82.5 D&M 1.40E+00 1.35E-06
No. 12 Injection Test 82.5-102.5 D&M 1.07E+01 1.03E-05
No. 28 Injection Test 76-87.5 D&M 4.30E+00 4.16E-06
No. 28 Injection Test 87.5-107.5 D&M 3.00E-01 2.90E-06
No. 28 Injection Test 107.5-132.5 D&M 2.00E-01 1.93E-07
WMMW1 (7) Recovery 92-112 Peel (2) 3.00E+00 2.90E-06
WMMW3 (7) Recovery 67-87 Peel 2.97E+00 2.87E-06
WMMW5 (7) Recovery 95.5-133.5 H-E 1.31E+01 1.27E-05
WMMW5 (7) Recovery 95.5-133.5 Peel 2.10E+01 2.03E-05
WMMW11 (7) Recovery 90.7-130.4 H-E (3)1.23E+03 1.19E-03
WMMW11 (7) Single Well Drawdown 90.7-130.4 Peel 1.63E+03 1.58E-03
WMMW12 (7) Recovery 84-124 H-E 6.84E+01 6.61E-05
WMMW12 (7) Recovery 84-124 Peel 6.84E+01 6.61E-05
WMMW14 Single Well Drawdown 90-120 (5) H-E 1.21E+03 1.16E-03
WMMW14 Single Well Drawdown 90-120 (6) H-E 4.02E+02 3.88E-04
WMMW15 Single Well Drawdown 99-129 H-E 3.65E+01 3.53E-05
WMMW15 (7) Recovery 99-129 Peel 2.58E+01 2.49E-05
WMMW16 Injection Test 28.5-31.5 Peel 9.42E+02 9.10E-04
WMMW16 Injection Test 45.5-51.5 Peel 5.28E+01 5.10E-05
WMMW16 Injection Test 65.5-71.5 Peel 8.07E+01 7.80E-05
WMMW16 Injection Test 85.5-91.5 Peel 3.00E+01 2.90E-05
WMMW17 Injection Test 45-50 Peel 3.10E+00 3.00E-06
WMMW17 Injection Test 90-95 Peel 3.62E+00 3.50E-06
WMMW17 Injection Test 100-105 Peel 5.69E+00 5.50E-06
WMMW18 Injection Test 27-32 Peel 1.14E+02 1.10E-04
WMMW18 Injection Test 85-90 Peel 2.59E+01 2.50E-05
WMMW18 Injection Test 85-90 Peel 2.69E+01 2.60E-05
WMMW18 Injection Test 120-125 Peel 4.66E+00 4.50E-06
WMMW19 Injection Test 55-60 Peel 8.69E+00 8.40E-06
WMMW19 Injection Test 95-100 Peel 1.45E+00 1.40E-06
Geometric Mean 1.05E+01 1.01E-05
Entrada/Navajo Sandstones
WW-1 Recovery D'Appolonia (4) 3.80E+02 3.67E-04
WW-1 Multi-well drawdown D'Appolonia 4.66E+02 4.50E-04
WW-1,2,3 Multi-well drawdown D'Appolonia 4.24E+02 4.10E-04
Geometric Mean 4.22E+02 4.08E-04
Notes
(1) D&M = Dames & Moore, Environmental Report, White Mesa Uranium Project, January 1978.
(2) Peel = Peel Environmental Services, UMETCO Minerals Corp., Ground Water Study, White Mesa Facility, June 1994.
(3) H-E = Hydro-Engineering, Ground-Water Hydrology at the White Mesa Tailings Facility, July 1991.
(4) D'Appolonia, Assessment of the Water Supply System, White Mesa Project, Feb. 1981.
(5) Early test data.
(6) Late test data.
(7) Test data reanalyzed by TEC.
Hydraulic
Conductivity
(ft/yr)
Hydraulic
Conductivity
(cm/sec)
Boring/
Well Location Test Type Interval
(ft-ft)
Document
Referenced
H:\718000\hydrpt14\Titan_material_props.xls
TABLE 5
Properties of the Dakota/Burro Canyon Formation
White Mesa Uranium Mill
from TITAN (1994)
Dakota WMMW-16 26.4' - 38.4' 1.50 3.30 135.20 17.90 2.64 18.20 5.10 -- -- -- Sandstone
WMMW-16 37.8' - 38.4' 0.40 0.80 127.40 22.40 2.63 3.70 6.30 -- -- -- Sandstone
WMMW-17 27.0' - 27.5' 0.30 0.60 138.80 13.40 2.57 4.80 5.10 -- -- -- Sandstone
WMMW-17 49.0' - 49.5' 3.60 7.10 121.90 26.00 2.64 27.20 9.60 -- -- -- Sandstone
Burro Canyon WMMW-16 45.0' - 45.5' 5.60 12.60 140.90 16.40 2.70 77.20 --29.60 15.40 14.20 Sandy Mudstone
WMMW-16 47.5' - 48.0' 2.60 5.90 142.80 12.00 2.60 48.90 4.40 -- -- -- Sandstone
WMMW-16 53.5' - 54.1' 0.70 1.40 129.00 19.90 2.58 7.10 6.40 -- -- -- Sandstone
WMMW-16 60.5' - 61.0' 0.10 0.20 117.90 27.30 2.61 0.80 9.90 -- -- -- Sandstone
WMMW-16 65.5' - 66.0' 2.60 5.50 131.50 19.30 2.62 28.20 7.10 -- -- -- Sandstone
WMMW-16 73.0' - 73.5' 0.10 0.30 130.30 20.60 2.63 1.30 5.50 -- -- -- Sandstone
WMMW-16 82.0' - 82.4' 0.10 0.10 134.30 18.50 2.64 0.60 4.80 -- -- -- Sandstone
WMMW-16 90.0' - 90.7' 0.10 0.30 161.50 2.00 2.64 12.80 0.90 -- -- -- Sandstone
WMMW-16 91.1' - 91.4' 5.20 9.80 118.10 29.10 2.67 33.80 -- 33.70 16.20 17.50 Claystone
WMMW-17 104.0' - 104.5' *0.20 0.40 161.40 1.70 2.67 26.60 0.80 -- -- -- Sandstone*
Note:
*Data from this interval is actually from the Brushy Basin and is not included in the averages.
18.34 2.63 23.41 5.57Formation Average: 1.90 4.01 134.03
19.93 2.62 13.48 6.53Formation Average: 1.45
%
Plasticity
Index
Rock TypeWell No. and Sample
Interval
%
Moisture
Content
2.95 130.83
%
Saturation
%
Retained
Moisture
% Liquid
Limit
% Plastic
Limit
Moisture
Content,
Volumetric
Dry Unit
Weight
(lbs/cu ft)
%
Porosity
Particle
Specific
Gravity
Formation
H:\718000\hydrpt14\Titan_material_props.xls: T5-TITAN Formation Properties 5/15/2014
TABLE 6
Hydraulic Conductivity Estimates For Spring Flow Calculations
location k (cm/s) location k (cm/s) location k (cm/s)
DR-21 3.29E-05 DR-5 2.95E-05 DR-5 2.95E-05
DR-23 1.96E-05 DR-8 2.46E-08 MW-23 2.30E-07
DR-24 1.64E-05 DR-9 4.49E-04 MW-24 4.16E-05
DR-10 2.92E-06 MW-35 3.48E-04
DR-11 8.88E-06
MW-12 2.20E-05
MW-23 2.30E-07
MW-24 4.16E-05
MW-36 4.51E-04
geomean:2.19E-05 geomean:9.76E-06 geomean:1.77E-05
Notes:
k = hydraulic conductivity
cm/s = centimeters per second
Ruin Spring Westwater Seep Westwater Seep (2)
H:\718000\hydrpt2022\tables\T1_2_3_6_Hydraulic_props_4Q21.xls: T6-Springs 4/7/2022
TABLE 7
Hydraulic Conductivity Estimates For Travel Time Calculations
Paths 1, 2A, and 2B
location k (cm/s) location k (cm/s) location k (cm/s)
TWN-2 1.49E-05 TW4-5 u 4.60E-04 MW-4A u 1.10E-04
TWN-3 8.56E-06 TW4-5 c 1.00E-03 MW-4A c 1.40E-04
TWN-18 2.27E-03 TW4-9 u 3.90E-04 TW4-2 u 4.30E-05
TW4-21 1.90E-04 TW4-9 c 8.20E-04 TW4-2 c 5.70E-05
TW4-22 1.30E-04 TW4-10 u 2.60E-04 TW4-8 u 4.30E-05
TW4-24 1.60E-04 TW4-10 c 5.40E-04 TW4-8 c 5.70E-05
TW4-25 5.80E-05 TW4-18 u 3.90E-04 TW4-9 u 3.90E-04
TW4-37 1.43E-04 TW4-18 c 8.60E-04 TW4-9 c 8.20E-04
MW-11 1.40E-03 MW-26 u 7.90E-05 TW4-28 3.52E-04
MW-27 8.20E-05 MW-26 c 1.40E-04 TW4-32 9.53E-05
MW-30 1.00E-04 TW4-39 5.27E-05 TW4-38 6.40E-05
MW-31 7.10E-05
geomean:1.19E-04 geomean:3.23E-04 geomean:1.18E-04
Notes:
k = hydraulic conductivity
cm/s = centimeters per second
c = confined solution
u = unconfined solution

PATH 1 PATH 2A PATH 2B
near historical pond (near wildlife ponds) (near wildlife ponds)
(nitrate plume area (chloroform plume area (chloroform plume area
H:\718000\hydrpt2022\tables\T7_8_9_PATHCALCS21.xls: T7-paths 1, 2a, 2b 4/7/2022
TABLE 8
Hydraulic Conductivity Estimates for Travel Time Calculations
Paths 3-6
location k (cm/s) location k (cm/s) location k (cm/s)
DR-5 2.95E-05 DR-5 2.95E-05 DR-11 8.88E-06
DR-8 2.46E-08 DR-8 2.46E-08 DR-13 5.89E-06
DR-9 4.49E-04 DR-9 4.49E-04 DR-21 3.29E-05
DR-10 2.92E-06 DR-10 2.92E-06 DR-23 1.54E-05
DR-11 8.88E-06 DR-11 8.88E-06 MW-3 4.00E-07
MW-12 2.20E-05 DR-14 1.26E-05 MW-14 7.50E-04
MW-23 2.30E-07 DR-17 1.24E-05 MW-15 1.90E-05
MW-24 4.16E-05 DR-19 3.29E-05 MW-20 9.30E-06
MW-36 4.51E-04 DR-20 2.14E-06 MW-37 1.28E-05
DR-21 3.29E-05
DR-23 1.96E-05
DR-24 1.64E-05
MW-23 2.30E-07
MW-24 4.16E-05
MW-36 4.51E-04
geomean:9.76E-06 geomean:1.10E-05 geomean:1.38E-05
Notes:
k = hydraulic conductivity
cm/s = centimeters per second
tailings management tailings management
PATHS 3 and 4 PATH 5 PATH 6
(downgradient of
system)
(downgradient of
system)
(downgradient of
system)
tailings management
H:\718000\hydrpt2022\tables\T7_8_9_PATHCALCS21.xls: T8-paths 3-6 4/7/2022
TABLE 9
Estimated Perched Zone Pore Velocities Along Path Lines
Path Length Head Change Hydraulic Gradient Pore Velocity General Path Location
(cm/s) (ft/yr) (ft) (ft) (ft/ft) (ft/yr) (area of site)
1 1.19E-04 122 1,940 32 0.0165 11 nitrate plume area near historical pond
2A 3.23E-04 330 1,045 36 0.0344 63 chloroform plume area near wildlife ponds
2B 1.18E-04 121 1,080 61 0.0565 38 chloroform plume area near wildlife ponds
3 9.76E-06 10.0 2,200 30 0.0136 0.76 downgradient of tailings mgmt system
4 9.76E-06 10.0 4,125 19 0.0046 0.26 downgradient of tailings mgmt system
5 1.10E-05 11.3 11,800 113 0.0096 0.60 downgradient of tailings mgmt system
6 1.38E-05 14.1 9,700 113 0.0116 0.91 downgradient of tailings mgmt system
Notes:
a Geometric average (from Tables 7 and 8)
Assumes effective porosity of 0.18
cm/s = centimeters per second
ft/ft = feet per foot
ft/yr = feet per year
mgmt = management
Path Hydraulic Conductivitya
H:\718000\hydrpt2022\tables\T7_8_9_PATHCALCS21.xls: T9-pore velocities 4/7/2022
TABLE 10
Results of XRD and Sulfur Analysis
in Weight Percent
Mineral Formula MW-3A MW-23 MW-24 MW-25 MW-26 MW-27 MW-28 MW-29 MW-30 MW-31
MW-32
(TW4-17)SS-26*
89.5 108 118.5 65 - 67.5 90 - 92.5 80 - 82.5 88.5 102 65 - 67.5 95 - 97.5 105-107.5 NA
quartz SiO2 79.7 96.2 88.4 90 86.9 95.4 90.1 95.8 87 91.7 94.1 39.2
K-feldspar KAlSi3O8 ND 0.2 0.6 2.4 2.4 0.7 1.5 0.5 1.4 2 0.8 21.6
plagioclase (Na,Ca)(Si,Al)4O8 ND ND ND 1.4 1.6 1.5 1.8 1.5 1.5 0.5 0.2 29
mica KAl2(Si3Al)O10(OH)2 0.3 1.2 4.5 2.2 2 0.2 3 0.2 5.9 3.1 1.2 5.2
kaolinite Al2Si2O5(OH)4 1.1 1 4.3 3.2 2.5 1.4 2.9 1.7 3.6 2.4 1.6 0.8
calcite CaCO3 14 ND ND ND 3.9 ND ND ND ND ND 1.2 0.6
dolomite CaMg(CO3)2 4.1 ND ND ND ND ND ND ND ND ND ND ND
anhydrite CaSO4 0.4 0.8 0.4 0.4 ND ND ND ND ND ND ND ND
gypsum CaSO4·2H2O ND 0.2 0.8 ND ND ND 0.3 ND 0.3 ND ND ND
iron Fe 0.3 0.4 0.2 0.4 0.4 0.4 0.2 0.3 0.3 0.3 0.4 0.2
pyrite FeS2 0.1 ND 0.8 ND 0.3 0.4 0.2 ND ND ND 0.5 ND
hematite Fe2O3 ND ND ND ND ND ND ND ND ND ND ND 1.4
magnetite Fe3O4 ND ND ND ND ND ND ND ND ND ND ND 2
Total S S 0.14 0.14 0.63 0.05 0.13 0.15 0.04 0.03 0.02 0.02 0.26 0.02
equivalent FeS2 FeS2 0.3 0.3 1.2 0.1 0.2 0.3 0.1 0.1 <0.1 <0.1 0.5 <0.1
Notes:
NA = Not applicable: quality control sample
ND = Not Detected
* = 'play sand'
Sulfur Determination
Depth (feet)
H:\718000\hydrpt2022\
Pyrite_results_tables_4Q21.xls: Table 10 4/8/2022
TABLE 11
Tabulation of Presence of
Pyrite, Iron Oxide, and Carbonaceous Fragments in Drill Logs
Well Pyrite C Fragments Iron Oxide
MW-3A X
aMW-16 X
aMW-17 X
aMW-18 X
aMW-19 X
aMW-20 X
aMW-21 X X
aMW-22 X
MW-23 X
MW-24 X
MW-25 X X
MW-26 X X
MW-27 X X
MW-28 X
MW-29 X
MW-30 X X
MW-31 X X
MW-32 X X
MW-33 X
MW-34 X X X
MW-35 X X X
MW-36 X X
MW-37 X X
MW-38 X
MW-39 X X
MW-40 X X
Piez-2 X
Piez-4 X X
Piez-5 X X
DR-2 X X
DR-5 X X
DR-6 X X
DR-7 X
DR-8 X
DR-9 X X
DR-10 X
DR-11 X X
DR-12 X X
DR-13 X
DR-14 X X
DR-15 X X
DR-16 X X
DR-17
DR-18 X X
DR-19 X
DR-20 X X
DR-21 X
DR-22
DR-23 X X
DR-24 X X
DR-25 X X
TW4-1 X
TW4-2 X X
TW4-3 X X X
TW4-4
TW4-5 X X
TW4-6 X X X
TW4-7 X X X
TW4-8 X
TW4-9 X X X
TW4-10 X X
H:\718000\hydrpt2022\
Pyrite_results_tables_4Q21.xls: Table 11 Page 1 of 2 4/8/2022
TABLE 11
Tabulation of Presence of
Pyrite, Iron Oxide, and Carbonaceous Fragments in Drill Logs
Well Pyrite C Fragments Iron Oxide
TW4-11 X
TW4-12 X X X
TW4-13 X X X
TW4-14 X
TW4-15 X X
TW4-16 X X
TW4-17 X X
TW4-18 X X
TW4-19 X
TW4-20 X
TW4-21 X X
TW4-22 X
TW4-23 X X X
TW4-24 X
TW4-25 X X
TW4-26 X
TW4-27 X X
TW4-28 X X
TW4-29 X X X
TW4-30 X X X
TW4-31 X X X
TW4-32 X X X
TW4-33 X X
TW4-34 X X
TW4-35 X X X
TW4-36 X X X
TW4-37 X
TW4-38 X
TW4-39 X X
TW4-40 X
TW4-41 X X
TW4-42 X X
TW4-43 X
TWN-1 X
TWN-2 X X
TWN-3 X X
TWN-4 X
TWN-5 X X
TWN-6 X X
TWN-7 X
TWN-8 X X
TWN-9 X
TWN-10 X
TWN-11 X X
TWN-12 X X
TWN-13 X X
TWN-14 X X
TWN-15 X X
TWN-16 X X
TWN-17 X
TWN-18 X X
TWN-19 X X
TWN-20 X X
TWN-21 X X
Notes:
C Fragments = particles of carbonaceous material (plant remains, etc)
a = only moderately detailed log available
H:\718000\hydrpt2022\
Pyrite_results_tables_4Q21.xls: Table 11 Page 2 of 2 4/8/2022
TABLE 12
Sulfide Analysis by Optical Microscopy
Grain size (micrometers)
Sample Depth (feet) Mineral Volume% Minimum Maximum Mean
MW-26 (TW4-15)1 92.5’ - 97.5' pyrite 4.30 5.6 44.4 128.9
MW-34 67.5’ - 70' pyrite 0.30 1.1 177.8 71.1
MW-36 87.5’ - 90' pyrite 5.20 5.6 88.9 52.2
MW-36 87.5’ - 90' marcasite 0.50 22.2 488.8 121.2
MW-36 112.5’ - 115' pyrite 2.20 16.7 577.7 188.9
MW-36 112.5’ - 115' marcasite 0.20 22.2 333.3 177.8
MW-37 110’ - 112.5' pyrite 9.80 11.1 1666.5 131.1
TW4-162 92.5’ - 95' pyrite 0.10 11.1 105.5 47.8
TW4-22 90’ - 92.5' pyrite 0.30 5.6 66.7 26.7
TWN-5 110’ - 112.5' pyrite 15.80 5.6 1377.6 208.9
TWN-5 112.5’ - 115' pyrite 0.50 5.6 266.6 70
TWN-5 112.5’ - 115' marcasite 0.50 22.2 55.6 36.7
TWN-5 112.5’ - 115' chalcopyrite 0.02 ND ND 6
TWN-8 117.5’ - 120' pyrite 12.00 5.6 455.1 137.8
TWN-8 117.5’ - 120' marcasite 0.60 66.6 288.9 155.5
AWN-X23 87.5’ - 90' pyrite 2.40 5.6 33.3 17.8
AWN-X23 87.5’ - 90' marcasite 0.60 66.6 288.9 155.5
TWN-164 82.5’ - 85' pyrite 0.10 1.1 11.1 6.1
TWN-164 87.5' - 90' pyrite 0.16 7 168 35.5
TWN-164 87.5' - 90' marcasite 0.05 ND 129.5 ND
TWN-195 82.5 ' - 85' pyrite 1.18 3.5 434 42.1
TWN-195 82.5 ' - 85' marcasite 0.06 21 42 36.4
DR-9 105’ - 107.5' pyrite 17.00 2.2 677.7 136.7
DR-12 87.5’ - 90' pyrite 0.30 11.1 111.1 52.2
DR-12 87.5’ - 90' marcasite 0.10 22.2 111.1 72.2
DR-16 97.5’ - 100' pyrite 2.40 5.6 33.3 17.8
DR-16 97.5’ - 100' marcasite 0.60 66.6 288.9 155.5
DR-25 75’ - 77.5' pyrite 25.00 1.1 1955 22
DR-25 75’ - 77.5' marcasite 2.50 55.6 621.6 265.5
SS-31*NA chalcopyrite 0.01 ND ND 10
SS-37*NA pyrite 0.02 7 14 11.7
Notes:
1 Samples from 92.5' - 95' and 95' - 97.5' combined due to small sample volume
2 Sample from 92.5' - 95' submitted instead of sample from 95' - 97.5' because no sample material available
3 Originally TWN-16
4 Originally TWN-19
5 Originally TWN-22
NA = Not applicable: quality control sample
ND = Not determined
* = 'play sand'
H:\718000\hydrpt2022\
Pyrite_results_tables_4Q21.xls: Table 12 4/8/2022
TABLE 13
Summary of
Pyrite in Drill Cuttings and Core
Well Pyrite Noted in Drill Logs Pyrite Detected by Laboratory
MW-3A X (Q)
aMW-16 NA
aMW-17 NA
aMW-18 NA
aMW-19 NA
aMW-20 NA
aMW-21 X NA
aMW-22 NA
MW-23 possibleb (Q)
MW-24 X (Q)
MW-25 X possibleb (Q)
MW-26 X X (Q)
MW-27 X X (Q)
MW-28 X (Q)
MW-29 possibleb (Q)
MW-30 X ND (Q)
MW-31 X ND (Q)
MW-32 X X (Q)
MW-33 NA
MW-34 X X (V)
MW-35 X NA
MW-36 X X (V)
MW-37 X X (V)
MW-38 NA
MW-39 X NA
MW-40 X NA
Piez-2 NA
Piez-4 X NA
Piez-5 X NA
DR-2 X NA
DR-5 X NA
DR-6 X NA
DR-7 NA
DR-8 NA
DR-9 X X (V)
DR-10 NA
DR-11 X NA
DR-12 X X (V)
DR-13 NA
DR-14 X NA
DR-15 X NA
DR-16 X X (V)
DR-17 NA
DR-18 X NA
DR-19 NA
DR-20 X NA
DR-21 NA
DR-22 NA
DR-23 X NA
DR-24 X NA
DR-25 X X (V)
TW4-1 NA
TW4-2 X NA
TW4-3 X NA
TW4-4 NA
TW4-5 X NA
TW4-6 X NA
TW4-7 X NA
TW4-8 NA
TW4-9 X NA
TW4-10 X NA
TW4-11 NA
TW4-12 X NA
TW4-13 X NA
H:\718000\hydrpt2022\
Pyrite_results_tables_4Q21.xls: Table 13 Page 1 of 2 4/8/2022
TABLE 13
Summary of
Pyrite in Drill Cuttings and Core
Well Pyrite Noted in Drill Logs Pyrite Detected by Laboratory
TW4-14 NA
TW4-15 X NA
TW4-16 X X (V)
TW4-17 X NA
TW4-18 NA
TW4-19 NA
TW4-20 NA
TW4-21 X NA
TW4-22 X X (V)
TW4-23 X NA
TW4-24 NA
TW4-25 X NA
TW4-26 NA
TW4-27 NA
TW4-28 X NA
TW4-29 X NA
TW4-30 X NA
TW4-31 X NA
TW4-32 X NA
TW4-33 X NA
TW4-34 NA
TW4-35 X NA
TW4-36 X NA
TW4-37 NA
TW4-38 NA
TW4-39 X NA
TW4-40 NA
TW4-41 X NA
TW4-42 X NA
TW4-43 NA
TWN-1 NA
TWN-2 X NA
TWN-3 X NA
TWN-4 NA
TWN-5 X X (V)
TWN-6 X NA
TWN-7 NA
TWN-8 X X (V)
TWN-9 NA
TWN-10 NA
TWN-11 X NA
TWN-12 X NA
TWN-13 X NA
TWN-14 X NA
TWN-15 X NA
TWN-16 X X (V)
TWN-17 NA
TWN-18 X NA
TWN-19 X X (V)
TWN-20 X NA
TWN-21 X NA
AWN-X1 NA
AWN-X2 X X (V)
AWN-X3 NA
Notes: a = only moderately detailed log available b = detected iron and sulfur may indicate the presence of pyrite
Q = quantiative analysis by XRD
V = visual (microscopic) analysis
ND = not detected by laboratory
NA = not analyzed by laboratory
H:\718000\hydrpt2022\
Pyrite_results_tables_4Q21.xls: Table 13 Page 2 of 2 4/8/2022
TABLE 14
Summary of Nitrate Degradation Rates
Source Type Pyrite Species Pyrite Weight %
Pyrite oxidation
rate (μM/h NO3-)
Pyrite oxidation rate
(NO3-N lbs/ft3/yr)
Torrento et al. (2010)Incubation Crystals of 25-100 μm 99.5 2.04 1.56E-02
Bosch et al. (2012)Incubation Nanoparticles of ~1 μm 100 38.56 2.95E-01
Jorgensen et al. (2009)Columns Crystals of 45-200 μm amended in sediment 1.0 0.05 3.83E-04
Torrento et al. (2010)Columns Crystals of 25-100 μm amended in sediment 99.5 4.67 3.58E-02
Zhang et al. (2009)Field study pyritic sands < 0.1 to 0.85 0.07 5.36E-04
White Mesa XRD Analysis Field study pyritic sands < 0.1 to 0.8 a5.4e-6 to 6.4e-6
Notes:
μM/h NO3- = micromoles per liter nitrate per hour
NO3-N lbs/ft3/yr = pounds per cubic foot per year nitarte as nitrogen
a =average based on HGC (2017)
H:\718000\hydrpt2022\Tables r1\T14_15_rate_summary_rev.xlsx: Table 14 - rates
TABLE 15
Pyrite Contents in Samples From White Mesa Mill and Oostrum, Netherlands Site
White Mesa Uranium Mill site Oostrum, Netherlands site
well depth (ft) Mill wt% pyrite (XRD)
1Mill 'equiv' wt% pyrite depth (m) depth (ft)
2Oostrum wt% pyrite
MW-3A 89.5 0.1 0.3 5.1 16.73 0
MW-23 108 0 0.3 5.2 17.06 0.01
MW-24 118.5 0.8 1.2 5.4 17.72 0.01
MW-25 66.25 0 0.1 7 22.97 0.01
MW-26 91.25 0.3 0.2 9.1 29.86 0
MW-27 81.25 0.4 0.3 9.3 30.51 0.01
MW-28 88.5 0.2 0.1 15.2 49.87 0.09
MW-29 102 0 0.1 19 62.34 0.85
MW-30 66.25 0 0 21.7 71.19 0.25
MW-31 96.25 0 0 23.3 76.44 0.49
MW-32 106.25 0.5 0.5 23.3 76.44 NA
25.8 84.65 0.37
27.5 90.22 0.29
29.2 95.80 0.09
31.2 102.36 0.08
33.2 108.92 0.19
35.3 115.81 0.09
36.9 121.06 0.38
37.2 122.05 NA
39.1 128.28 0.17
average 0.21 0.28 0.28 (pyritic depths only)
Notes:
XRD = X-ray diffraction
1 = Based on total iron and sulfur contents
2 = Based on total sulfur content
0 = not detected (< 0.1%)
m = meters
ft = feet
H:\718000\hydrpt2022\Tables r1\T14_15_rate_summary_rev.xlsx: Table 15 - pyrite content

FIGURES
HYDRO
GEO
CHEM, INC.
1 mile
WHITE MESA
Mill Site
WW-3
CORRAL CANYON
CORRAL SPRINGS
COTTONWOOD
ENTRANCE SPRING
RUIN SPRING
WESTWATER
Cell 1
Cell 2
Cell 3
Cell 4A
Cell 4B
MW-01
MW-02
MW-3A
MW-11
MW-14MW-15
MW-17
MW-18
MW-19
MW-20
MW-21
MW-22
MW-23
MW-24
MW-25
MW-27
MW-28
MW-29
MW-30
MW-31
MW-32
MW-33
MW-34MW-37
MW-38
MW-39
MW-40
TW4-01
TW4-03
TWN-01
TWN-02
TWN-03
TWN-04
TWN-05
TWN-06
TWN-07
TWN-08
TWN-09
TWN-10
TWN-11 TWN-12
TWN-13
TWN-14
TWN-15
TWN-16
TWN-17
TWN-18
TWN-19
TWN-20
TWN-21
PIEZ-01
PIEZ-02
PIEZ-3A
PIEZ-04
PIEZ-05
TW4-05
TW4-12
TW4-13
TW4-31
TW4-32
MW-12
TW4-11TW4-16
TW4-18
TW4-27
MW-26
MW-35
MW-36
TW4-04
TW4-07
TW4-09
TW4-19
TW4-21
TW4-24
TW4-25
TW4-26
TW4-40
TW4-06
TW4-42
TW4-02
TW4-08
MW-04
MW-05
TW4-22
TW4-23
TW4-20
TW4-28
TW4-29
TW4-30
TW4-10
TW4-33
TW4-34
TW4-36
TW4-41TW4-14
TW4-43TW4-35
TW4-37 TW4-38
TW4-39
DR-05 DR-06 DR-07
DR-08
DR-09
DR-10 DR-11 DR-12 DR-13
DR-14 DR-15
DR-17
DR-19 DR-20 DR-21
DR-22
DR-23
DR-24
abandoned abandoned
abandoned
abandoned
abandoned abandoned
abandoned
abandoned abandoned
DR-02
DR-16
DR-18
DR-25
abandoned
abandoned
abandoned
abandoned
MW-24A
MW-16abandoned
MW-3abandoned
W E
S
N
SW
NE
SW2
NE2
NW
SE
W2 E2
WNW
ESE
wildlife pond
wildlife pond
wildlife pond
abnd
EXPLANATION
perched monitoring well
perched piezometer
seep or spring
WHITE MESA SITE PLAN SHOWING LOCATIONS OF
PERCHED WELLS, PIEZOMETERS AND LITHOLOGIC
CROSS-SECTIONS (as of 4th quarter, 2021)
H:/718000/
hydrpt2022/figures/Uwellocxs2022_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
temporary perched nitrate monitoring well
TW4-12
TWN-7
TW4-19 perched chloroform or
nitrate pumping well
approximate footprint of historical pond
1A
perched monitoring well
installed February, 2018
MW-38
TW4-42
MW-24A
TWN-20
TW4-43
temporary perched monitoring well
installed April 2019
perched monitoring well installed
December 2019
temporary perched nitrate monitoring
well installed April, 2021
temporary perched monitoring well
installed September, 2021
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
historic pond footprint
Q4, 2021 nitrate plume boundary
Q4, 2021 chloroform plume boundary
H:/718000/
hydrpt2022/figures/UwlChlNt4Q21.srf 1BSJS
WHITE MESA SITE PLAN SHOWING 4th QUARTER 2021
PERCHED WELL AND PIEZOMETER LOCATIONS,
KRIGED PERCHED WATER LEVELS AND
CHLOROFORM AND NITRATE PLUMES
H:\718000\hydrpt2018\Figure2_7.xls: F2 litho clmn
LITHOLOGIC COLUMNHYDRO
GEO
CHEM, INC.Approved FigureDateAuthorDate File Name
SJS 11/9/12 2F2 litho clmn11/9/12SJS
B ur ro Canyon Fo rma t ion
Brushy Basin Member
Highway 95
Reference Outcrop Just North
of White Mesa Uranium Mill
HYDRO
GEO
CHEM, INC.
4
PHOTOGRAPH OF THE CONTACT BETWEEN THE
BURRO CANYON FORMATION AND THE
BRUSHY BASIN MEMBER
H:/718000/hydrpt2022/
Figures/contact2.srf
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
KRIGED 4th QUARTER, 2021 WATER LEVELS
WHITE MESA SITE
H:/718000/hyrpt2022/figures/Uwl1221det.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
5
saturated thickness estimated
to be less than 5 feet
5500
4th quarter 2021 water level
contour and label in feet amsl
SJS
HYDRO
GEO
CHEM, INC.
"Dry Seep""2nd Seep" (5240 ft amsl)Cottonwood Seep (5234 ft amsl)
Kdbc Kdbc
Jmbb
ss (within Jmw)
sh (Jmr)
(contact approx. 5465 ft amsl)
Approximate Location
of DR-8
EXPLANATION
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin (Shale) Member
Approximate Location of
Geologic Contact
Kdbc
Jmbb
sandstone (within Westwater
Canyon Member)
ss
(within Jmw)
shale (Recapture Member)sh (Jmr)
H:/718000/hydrpt2022/
Figures/cottonwood2.srf
ANNOTATED PHOTOGRAPH SHOWING
EAST SIDE OF COTTONWOOD CANYON
(looking east toward White Mesa
from west side of Cottonwood Canyon)
NOTES: adapted from HGC (2010); "2nd Seep" and "Dry Seep" are described in HGC (2010)
Approximate Change From
Slope-Former to Bench-Former
Jmbb Jmbb
WHITE MESA
(slope-former)
(cliff-former)
(cliff-former)(cliff-former)
(slope-former)(slope-former)
COTTONWOOD CANYON
lower Jmbb/upper Jmw
(bench former)
lower Jmbb/upper Jmw
(bench former)
(slope-former)
6
H:\718000\hydrpt2018\Figure2_7.xls: F7 west int sea
EXTENT OF THE WESTERN INTERIOR SEA
(CRETACEOUS)
HYDRO
GEO
CHEM, INC.Approved FigureDateAuthorDate File Name
SJS 11/9/12 7F7 west int sea11/9/12SJS
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl (X = abandoned)
KRIGED TOP OF BRUSHY BASIN
WHITE MESA SITE
H:/718000/hydrpt2022/figures/Ubbel1221_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5491
5521
5545
5552
MW-38
5459
TW4-42
5508
TWN-20
5546
8seep or spring showing
elevation in feet amsl5380
5 3 8 0 kriged top of Brushy Basin elevation
contour and label (feet amsl)
approximate axis of Brushy Basin
paleoridge
approximate axis of Brushy Basin
paleovalley
TW4-43 temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl5504
temporary perched nitrate monitoring
well installed April, 2021 showing
elevation in feet amsl
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl (X = abandoned)
KRIGED TOP OF BEDROCK
WHITE MESA SITE
H:/718000/hydrpt2022/
figures/Ubdrkel1221_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5579
5602
5637
5640
MW-38
5525
TW4-42
5587
TWN-20
5626
9Aseep or spring
5 4 6 0 kriged top of bedrock elevation
contour and label (feet amsl)
TW4-43 temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl5590
temporary perched nitrate monitoring
well installed April, 2021 showing
elevation in feet amsl
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl (X = abandoned)
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5579
5602
5637
5649
MW-38
5531
TW4-42
5587
TWN-20
5626
9Bseep or spring
5 4 6 0 kriged top of bedrock elevation
contour and label (feet amsl)
TW4-43 temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl5590
KRIGED TOP OF BEDROCK
USING REVISED DEPTH TO MANCOS DATA
WHITE MESA SITE
H:/718000/hydrpt2022
figures/Ubdrkel1221_rev2.srf
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl (X = abandoned)
KRIGED TOP OF DAKOTA
WHITE MESA SITE
H:/718000/hydrpt2022/
figures/Udakotael1221_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5579
5591
5625
5640
MW-38
5525
TW4-42
5572
TWN-20
5623
10seep or spring
5 4 6 0 kriged top of Dakota elevation
contour and label (feet amsl)
TW4-43 temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl5563
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl (X = abandoned)
KRIGED TOP OF BEDROCK
SHOWING APPROXIMATE MANCOS THICKNESS
WHITE MESA SITE
H:/718000/hydrpt2022/
figures/Ubdrkmanc_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5579
5602
5637
5640
MW-38
5525
TW4-42
5587
TWN-20
5626
11Aseep or spring
5 3 8 0 kriged top of bedrock elevation
contour and label (feet amsl)
TW4-43 temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl5590
2.5 5 10 20 30
approximate Mancos thickness (feet)
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl (X = abandoned)
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5579
5602
5637
5649
MW-38
5531
TW4-42
5587
TWN-20
5626
11Bseep or spring
5 3 8 0 kriged top of bedrock elevation
contour and label (feet amsl)
TW4-43 temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl5590
KRIGED TOP OF BEDROCK SHOWING
APPROXIMATE REVISED MANCOS THICKNESS
WHITE MESA SITE
H:/718000/hydrpt2022
figures/Ubdrkmanc_rev2.srf
2.5 5 10 20 30
approximate Mancos thickness (feet)
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
HYDRO
GEO
CHEM, INC.
P7
C-01
P7C-02
P7
C-03
P8
C-01
P8C-02P8
C-03
P8C-04
P
9C-01 P9
C-02
P9
C-03
P9C-04
P9
C-05
P10
C-01
P10
C-02
P10
C-03
P
11C-01
P11
C-02
P11
C-03
P11C-04
P11
C-05
P12C-01
P12C-02
P12C-03
P
13C-01
P
13C-02
P
13C-03
P14C-01
P14C-02
P
14C-03
P15C-01
P16
C-01P16C-02
P16C-03
P16
C-04
P16
C-05
P
17C-01
P17
C-02
P
17C-03
P17
C-04
P
18C-01
P18
C-02
P18C-03
P1A-01
P2A-01
P3A-N01
P4A-01
P5A-01
P1A-08
P2A-08
P3A-08
P4A-10
P5A-10
P6A-01
P6A-04
100 feet
EXPLANATION APPROXIMATE GEOPROBE BORING
AND CROSS-SECTION LOCATIONS
WHITE MESA SITE
H:/718000/hydrpt2022/
xsections/soilxs/soilxsloc_rev.srf
approximate 1st sampling event geoprobe boring location
approximate 2nd sampling event geoprobe boring location
approximate 3rd sampling event geoprobe boring location
ammonium sulfate crystal tank
north-south (N-S) cross-section
northeast - southwest (NE-SW) cross-section
HYDRO
GEO
CHEM, INC.
SOIL CROSS SECTIONS
EAST OF AMMONIUM SULFATE CRYSTAL TANKS
WHITE MESA SITE
S N
EXPLANATION
weathered mancos shale
competent bedrock
asphalt
primarily sand primarily clay
primarily silt
vertical exaggeration = 2:1
Note: NH3 xtal tanks 60 feet west of section
0 50 100 150 200 250 300
distance (feet)
5610
5615
5620
5625
5630
5635
5640
5645
ap
p
r
o
x
i
m
a
t
e

e
l
e
v
a
t
i
o
n

(
f
t

a
m
s
l
)
NH
3

x
t
a
l

t
a
n
k
s
P1
7
C
-
0
1
P1
6
C
-
0
1
P1
4
C
-
0
1
P1
3
C
-
0
1
P1
2
C
-
0
1
P1
A
-
0
8
P1
A
-
0
7
P1
A
-
0
6
P1
A
-
0
5
P1
A
-
0
4
P1
A
-
0
3
P1
A
-
0
2
P2
A
-
0
1
P3
A
-
N
0
1
P4
A
-
0
1
P5
A
-
0
1
P1
1
C
-
0
4
P1
1
C
-
0
3
P1
1
C
-
0
2
silt/clay
0 50 100
distance (feet)
5605
5610
5615
5620
5625
5630
5635
5640
5645
ep
p
r
o
x
i
m
a
t
e

e
l
e
v
a
t
i
o
n

(
f
t

a
m
s
l
)
P1
A
-
0
3
P2
A
-
0
3
P3
A
-
0
3
P4
A
-
0
5
P5
A
-
0
5
P6
A
-
0
2
P8
C
-
0
1
P9
C
-
0
1
P1
0
C
-
0
1
SW NE
H:/718000/hydrpt2022/
Figures/soilxs.srf 13
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
thickness in feet
perched piezometer showing
thickness in feet
4th QUARTER, 2021
SATURATED THICKNESS IN FEET
WHITE MESA SITE
H:/718000/hydrpt2022/figures/Usat1221_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing thickness in feet
temporary perched nitrate monitoring
well showing thickness in feet
TW4-12
TWN-7
12
47
24
37
MW-38
4
TW4-42
17
TWN-20
19
14seep or spring
approximate axis of Brushy Basin
paleoridge
approximate axis of Brushy Basin
paleovalley
TW4-43 temporary perched monitoring
well installed September, 2021
showing thickness in feet20
estimated dry area
saturated thickness estimated
to be less than 5 feet
Note: Q4 2021 water levels for TW4-1, TW4-2 and TW4-11 are below the base of the Burro Canyon Formation
temporary perched nitrate monitoring
well installed April, 2021 showing
thickness in feet
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
depth to water in feet
perched piezometer showing
depth to water in feet
4th QUARTER, 2021
DEPTH TO WATER IN FEET
WHITE MESA SITE
H:/718000/hydrpt2022/figures/Udtw1221_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing depth to water in feet
temporary perched nitrate monitoring
well showing depth to water in feet
TW4-12
TWN-7
108
56
81
67
MW-38
70
TW4-42
70
TWN-20
78
15seep or spring
TW4-43 temporary perched monitoring
well installed September, 2021
showing depth to water in feet73
estimated dry area
saturated thickness estimated
to be less than 5 feet
Note: Q4 2021 water levels for TW4-1, TW4-2 and TW4-11 are below the base of the Burro Canyon Formation
temporary perched nitrate monitoring
well installed April, 2021 showing
depth to water in in feet
EXPLANATION
Qaf
Km
Kdbc
Jmbb
Alluvium/Fill/
Weathered Mancos
Mancos Shale
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member of
Morrison Formation
Shale/claystone in Dakota /
Burro Canyon Formation
Conglomerate in Dakota /
Burro Canyon Formation
SW NE
Piezometric Surface
vertical exaggeration = 20 : 1
0 2000 4000 6000 8000 10000 12000
distance (feet)
5420
5440
5460
5480
5500
5520
5540
5560
5580
5600
5620
5640
5660
5680
5700
5720
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
MW
-
0
3
*
MW
-
1
4
MW
-
1
1
MW
-
3
1
TW
4
-
2
4
MW
-
2
7
TW
N
-
2
TW
N
-
3
TW
N
-
1
8
TW
N
-
8
*
TW
N
-
6
TW
N
-
1
0
*

TW
N
-
1
5
*

TW
N
-
1
6
TW
N
-
1
2
*
Cell # 4A
Cell # 3
Cell # 2 Cell # 1
Fl
y

A
s
h

P
o
n
d
Ce
l
l

1

L
e
a
c
h

F
i
e
l
d
CC
D
/
S
X

L
e
a
c
h

F
i
e
l
d
Hi
s
t
o
r
i
c
a
l

P
o
n
d
La
w
z
y

L
a
k
e
Kdbc
Kdbc
Kdbc
Km
Km
Km
Jmbb
Jmbb
Jmbb
Qaf
Qaf
Notes: 1) water levels from TWN-8, TWN-10, TWN-12,
and TWN-15 are estimated by kriging;
2) lithology for MW-3 from log of MW-3A
* denotes abandoned boring
16AH:/718000/
hydrpt2022/xsections/nsxsne/nsxsne18b.srf
HYDRO
GEO
CHEM, INC.
SW2 NE2
INTERPRETIVE NORTHEAST-SOUTHWEST
CROSS SECTION (NE2-SW2)
WHITE MESA SITE
EXPLANATION
Qaf
Kdbc
Jmbb
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member of
Morrison Formation
Shale/claystone in Dakota /
Burro Canyon Formation
Conglomerate or Conglomeratic
Sandstone in Dakota /
Burro Canyon Formation
Piezometric Surface
TW
N
-
1
8
MW
-
1
9
PI
E
Z
-
1
TW
N
-
9
*
TW
N
-
1
4
TW
N
-
1
7
*
TW
N
-
1
9
Law
zy

L
a
k
e

(
1
)
Wi
l
d
l
i
f
e

P
ond

(
2
)
5450
5470
5490
5510
5530
5550
5570
5590
5610
5630
5650
5670
5690
5710
5730
5750
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
distance (feet)
Notes: (1) approximately 200 feet north of cross section
(2) approximately 200 feet south of cross section
vertical exaggeration = 8 : 1
SJS
Note: water levels from TWN-9
and TWN-17 are
estimated by kriging
* denotes abandoned boring
H:/718000/hydrpt2022/
xsections/nsxs2ne/nsxs2ne18b.srf 16B
Alluvium/Fill/
Weathered Mancos
HYDRO
GEO
CHEM, INC.
0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200
distance (feet)
5460
5480
5500
5520
5540
5560
5580
5600
5620
5640
5660
5680
5700
5720
5740
5760
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
TW
N
-
7

TW
N
-
2

TW
4
-
2
5
TW
4
-
2
1
TW
N
-
1

PI
E
Z
-
3
*
Hi
s
t
o
r
i
c
a
l

P
o
n
d
La
w
z
y

S
u
m
p
SA
G

L
e
a
c
h

F
i
e
l
d
Am
m
o
n
i
u
m

S
u
l
f
a
t
e

T
a
n
k
s

(
1
)
Am
m
o
n
i
a

T
a
n
k
s

(
2
)
Fo
r
m
e
r

O
f
f
i
c
e

L
e
a
c
h

F
i
e
l
d

(
3
)
Ma
i
n

L
e
a
c
h

F
i
e
l
d

(
4
)
QafKm
Km Km
Kdbc
Kdbc
Kdbc
Jmbb
Jmbb
Notes: (1) approximately 115 feet southwest of cross-section
(2) approximately 150 feet southwest of cross-section
(3) approximately 300 feet south of cross-section
(4) immediately south of cross-section
EXPLANATION
Qaf
Km
Kdbc
Jmbb
Mancos Shale
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member of
Morrison Formation
Shale/claystone in Dakota /
Burro Canyon Formation
Conglomerate or Conglomeratic
Sandstone in Dakota /
Burro Canyon Formation
Piezometric Surface INTERPRETIVE NORTHWEST-SOUTHEAST
CROSS SECTION (NW-SE)
WHITE MESA SITE
NW SE
vertical exaggeration = 3 : 1
SJS H:/718000/hydrpt2022/
xsections/ewxsne/ewxsne18b.srf 17
Note: water level shown for
Piez-3 is from replacement
piezometer Piez-3A
Alluvium/Fill/
Weathered Mancos
APPROVED DATE REFERENCE FIGURE
HYDRO
GEO
CHEM, INC.
EXPLANATION
Qal
Km
Kdbc Jmbb
Mancos Shale
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member
of Morrison Formation
Piezometric surface
vertical exaggeration = 5:1
Shale/claystone within
Dakota/Burro Canyon
Conglomerate within
Dakota/Burro Canyon
INTERPRETIVE EAST-WEST
CROSS SECTIONS (W-E and W2-E2)
SOUTHWEST INVESTIGATION AREA
0 500 1000 1500 2000 2500 3000 3500
distance (feet)
5450
5475
5500
5525
5550
5575
5600
5625
5650
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
DR
-
2

(
a
b
n
d
)
DR
-
5
DR
-
6
DR
-
7
MW
-
3
5
W E
Qal
Km
Kdbc
Kdbc
Jmbb Jmbb
18A H:/718000/hydrpt2022/
xsections/ewxssw/ewxssw2b_rev3.srf
Note: water level for abandoned piezometer DR-2
is from the second quarter of 2011
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500
distance (feet)
5450
5475
5500
5525
5550
5575
5600
5625
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
DR
-
8
DR
-
9
DR
-
1
0
DR
-
1
1
DR
-
1
2
DR
-
1
3
MW
-
1
7
Qal
Km Km
Kdbc Kdbc
Jmbb
Jmbb
W2 E2
vertical exaggeration = 10:1
Conglomeratic Dakota Sandstone/
Burro Canyon Formation
SJS
Alluvium/Fill/
Weathered Mancos
APPROVED DATE REFERENCE FIGURE
HYDRO
GEO
CHEM, INC.
EXPLANATION
Qal/Fill
Km
Kdbc
Jmbb
Mancos Shale
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member
of Morrison Formation
Piezometric surface
vertical exaggeration = 5:1
Shale/Shaly Sandstone within
Dakota/Burro Canyon
Conglomerate within
Dakota/Burro Canyon
INTERPRETIVE EAST-WEST
CROSS SECTION (WNW - ESE)
SOUTHWEST INVESTIGATION AREA
H:/718000/hydrpt2022/
xsections/ewxssw3/ew3xsectb_rev2.srf
* = detailed log unavailable
Conglomeratic Dakota Sandstone/
Burro Canyon Formation
SJS
0 500 1000 1500 2000 2500 3000 3500
distance (feet)
5450
5475
5500
5525
5550
5575
5600
5625
5650
5675
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
DR
-
7
MW
-
3
6
MW
-
3
3
MW
-
3
4
MW
-
3
7
MW
-
1
5
*
MW
-
1
4
*
MW
-
1
7
Qal/Fill Qal/FillKm
Kdbc
Kdbc
Jmbb
WNW ESE
south dike Cell 4B south dike Cell 4A
18B
Alluvium/Fill/
Weathered Mancos
HYDRO
GEO
CHEM, INC.
EXPLANATION
Qal
Km
Kdbc Jmbb
Mancos Shale
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member
of Morrison Formation
Piezometric surface
INTERPRETIVE NORTH-SOUTH
CROSS SECTION (S-N)
SOUTHWEST INVESTIGATION AREA
vertical exaggeration = 20:1
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
distance (feet)
5375
5400
5425
5450
5475
5500
5525
5550
5575
5600
5625
el
e
v
a
t
i
o
n

(
f
e
e
t
)
Ru
i
n

S
p
r
i
n
g
DR
-
2
5

(
a
b
n
d
)
DR
-
2
1
MW
-
2
0
DR
-
1
6

(
a
b
n
d
)
MW
-
3
DR
-
1
3
MW
-
3
7
Qal
Km
Km
Km
Kdbc
Kdbc
Jmbb
Jmbb
S N
Shale/claystone within
Dakota/Burro Canyon
Conglomerate within
Dakota/Burro Canyon
H:/718000/hydrpt2022/
xsections/nsxssw/nsxssw18b.srf 19
Notes: water levels for abandoned
piezometers DR-16 and DR-25
are from the second quarter of
2011; MW-3 lithology from MW-3A SJS
Alluvium/Fill/
Weathered Mancos
H:\718000\hydrpt2022\DR_ Hydrographs_4Q21.xls: DR Piez Hydrographs
40
50
60
70
80
90
100
110
Q2
11
Q3
11
Q4
11
Q1
12
Q2
12
Q3
12
Q4
12
Q2
13
Q3
13
Q4
13
Q1
14
Q2
14
Q3
14
Q4
14
Q1
15
Q2
15
Q3
15
Q4
15
Q1
16
Q2
16
Q3
16
Q4
16
Q1
17
Q2
17
Q3
17
Q4
17
Q1
18
Q2
18
Q3
18
Q4
18
Q1
19
Q2
19
Q3
19
Q4
19
Q1
20
Q2
20
Q3
20
Q4
20
Q1
21
Q2
21
Q3
21
Q4
21
De
p
t
h

t
o

W
a
t
e
r

(
f
e
e
t

b
t
o
c
)
Quarter
DR-5 DR-6 DR-7 DR-8 DR-9 DR-10
DR-11 DR-12 DR-13 DR-14 DR-15 DR-17
DR-19 DR-20 DR-21 DR-23 DR-24
DR-SERIES PIEZOMETER DEPTHS TO WATER
2Q 2011 TO 4Q 2021
HYDRO
GEO
CHEM, INC.Approved FigureDateAuthorDate File Name
SJS 20DR Piez HydrographSJS
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
H:/718000/hyrpt2022/
figures/Uflow1221Nchl_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
21
saturated thickness estimated
to be less than 5 feet
KRIGED 4th QUARTER, 2021 WATER LEVELS
SHOWING INFERRED PERCHED WATER PATHLINES
AND KRIGED NITRATE AND CHLOROFORM PLUMES
kriged chloroform > 70 ug/L
kriged nitrate > 10 mg/L within area
addressed by nitrate CAP
estimated total pumping capture
estimated perched water flow path
SJS
HYDRO
GEO
CHEM, INC.
5520
5525
5526.25
5527.5
5530
5 5 4 5
5 5 5 05552.5
5 5 6 0
5 5 6 5
5 5 7 0
5 5 7 5
5 5 8 0
5 5 8 2 .5
5 5 8 5
EXPLANATION
perched monitoring well showing
elevation in feet amsl
temporary perched monitoring well
showing elevation in feet amsl
perched piezometer showing
elevation in feet amsl
MW-25
TW4-7
PIEZ-2
KRIGED 4th QUARTER, 2021 WATER LEVELS
AND ESTIMATED CAPTURE ZONES
WHITE MESA SITE
(detail map)
5532
5539
5583
5525
TW4-43
5524
TW4-42 temporary perched monitoring well
installed April, 2019 showing
elevation in feet amsl
temporary perched monitoring well
installed September, 2021 showing
elevation in feet amsl
22SJS
HYDRO
GEO
CHEM, INC.
1 mile
WHITE MESA
5390
5390 5410
5 4 1 0
5430
5 4 3 0
5450
5 4 5 0 5470
5470
5490
5
4
9
0
5 5 1 0
5
5
1
0
5530
5
5
3
0
5 5 5 0
5 5 7 0
5
5
7
0
55
9
0
5590
5600
5600
5610
CORRAL CANYON
CORRAL SPRINGS
COTTONWOOD
ENTRANCE SPRING
RUIN SPRING
WESTWATER
Cell 1
Cell 2
Cell 3
Cell 4A
Cell 4B
MW-01
MW-02
MW-03
MW-05
MW-11
MW-12
MW-14MW-15
MW-17
MW-18
MW-19
MW-20
MW-21
MW-22
MW-23
MW-24
MW-25
MW-26
MW-27
MW-28
MW-29
MW-30
MW-31
MW-32
MW-33
MW-34
MW-35
MW-36
MW-37
TW4-01
TW4-10
TW4-20TW4-22
TW4-23
TWN-01
TWN-02
TWN-03
TWN-04
TWN-05
TWN-06
TWN-07
TWN-08
TWN-09
TWN-10
TWN-11 TWN-12
TWN-13
TWN-14
TWN-15
TWN-16
TWN-17
TWN-18
TWN-19
PIEZ-01
PIEZ-02
PIEZ-03
PIEZ-04
PIEZ-05
TW4-02
TW4-05
TW4-06
TW4-09
TW4-11
TW4-12
TW4-13
TW4-14
TW4-16
TW4-18
TW4-27
TW4-19
TW4-26
TW4-04
TW4-07
TW4-21
TW4-24
TW4-25
TW4-03
TW4-08
MW-04
DR-05 DR-06 DR-07
DR-08
DR-09
DR-10 DR-11 DR-12 DR-13
DR-14 DR-15
DR-17
DR-19 DR-20 DR-21
DR-22
DR-23
DR-24
5581
5503
5471
5503
5523
5501
54945494
5500
5588
5603
5453
dry
5451
5495
5507
5539
5577
5544
5513
5538
5548
dry
5494
5493
5484
55795549
5550
55765571
5598
5594
5610
5598
5544
5542
5597
5610
5602
5603
5586
5591
5561
5590
5587
5586
5615 5639
5588
5587
5584
5605
5608
5588
5609
5583
5544
5539
5555
5584
5574
5526
5559
5586
5538
5518
5555
5558
5585
5584
55675563
55855571
5543
5493548354845492
5474
5480
5482 5487 5492 5487
5466 5465
5454
5455 5443 5420
dry
5425
5418
5624
5383
5234
5560
5380
5468
(not included)
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
KRIGED 4th QUARTER, 2011 WATER LEVELS
WHITE MESA SITE
H:/718000/hydrpt2022/figures/Uwl1211b.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
installed October, 2011 showing
elevation in feet amsl
TW4-27
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-10
5503
5584
5586
5594
5518
5380
Estimated dry area
NOTE: MW-4, MW-26, TW4-4, TW4-19, and TW4-20 are pumping wells
H:\718000\hydrpt2022\TW6wltrend_4Q21.xls: TW4_6 plot
5520
5525
5530
5535
5540
5545
5550
5555
Q4

0
7
Q1

0
8
Q2

0
8
Q3

0
8
Q4

0
8
Q1

0
9
Q2

0
9
Q3

0
9
Q4

0
9
Q1

1
0
Q2

1
0
Q3

1
0
Q4

1
0
Q1

1
1
Q2

1
1
Q3

1
1
Q4

1
1
Q1

1
2
Q2

1
2
Q3

1
2
Q4

1
2
Q1

1
3
Q2

1
3
Q3

1
3
Q4

1
3
Q1

1
4
Q2

1
4
Q3

1
4
Q4

1
4
Q1

1
5
Q2

1
5
Q3

1
5
Q4

1
5
Q1

1
6
Q2

1
6
Q3

1
6
Q4

1
6
Q1

1
7
Q2

1
7
Q3

1
7
Q4

1
7
Q1

1
8
Q2

1
8
Q3

1
8
Q4

1
8
Q1

1
9
Q2

1
9
Q3

1
9
Q4

1
9
Q1

2
0
Q2

2
0
Q3

2
0
Q4

2
0
Q1

2
1
Q2

2
1
Q3

2
1
Q4

2
1
Wa
t
e
r

L
e
v
e
l

(
f
t

a
m
s
l
)
Quarter
TW4-4
TW4-6
TW4-4 AND TW4-6 WATER LEVELSHYDRO
GEO
CHEM, INC.Approved FigureDateAuthorDateFile Name
SJS 24TW6 wltrend plotSJS
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
H:/718000/hyrpt2022/
figures/Uflowsw1221_rev.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
25
estimated area having saturated
thickness less than 5 feet
estimated perched water flow path
KRIGED 4th QUARTER, 2021 WATER LEVELS
SHOWING INFERRED PERCHED WATER PATHLINES
DOWNGRADIENT OF THE TAILINGS MANAGEMENT SYSTEM
WHITE MESA SITE
SJS
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl H:/718000/hyrpt2022/figures/Uspgflow1221.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
26
saturated thickness
estimated to be less than 5 feet
KRIGED 4th QUARTER, 2021 WATER LEVELS
SHOWING INFERRED PERCHED WATER FLOW
PATHLINES NEAR RUIN SPRING AND WESTWATER SEEP
inferred perched flow path
estimated saturated
thickness in feet15
SJS
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-42
TWN-20
TW4-43
5524
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well
perched piezometer
seep or spring showing
elevation in feet amsl
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
temporary perched nitrate monitoring
well
TW4-12
TWN-7
5380
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021
temporary perched monitoring
well installed September, 2021
TW4-43
TWN-20
saturated thickness estimated
to be less than 5 feet
5500
4th quarter 2021 water level
contour and label in feet amsl
KRIGED 4th QUARTER, 2021 WATER LEVELS
SHOWING INFERRED PERCHED WATER FLOW PATHS
USED FOR TRAVEL TIME ESTIMATES
AND KRIGED NITRATE AND CHLOROFORM PLUMES
H:/718000/hydrpt2022/
figures/UpathNchl4Q21_rev.srf 27
4th quarter 2021 chloroform plume
4th quarter 2021nitrate plume
potential perched water pathline
(assuming hypothetical connection
to Cottonwood Seep)
inferred perched water pathline
SJS
B ur ro Canyon Fo rma t ion
Brushy Basin Member
HYDRO
GEO
CHEM, INC.
28
PHOTOGRAPH OF THE WESTWATER SEEP
SAMPLING LOCATION
JULY, 2010
Westwater Seep
(sampling location)
B ur ro Canyon Fo rma t ion
Brushy Basin Member
HYDRO
GEO
CHEM, INC.
29
PHOTOGRAPH OF THE CONTACT BETWEEN THE
BURRO CANYON FORMATION AND THE
BRUSHY BASIN MEMBER
AT WESTWATER SEEP
H:/718000/hydrpt2022/
Figures/westcontact2.srf
Westwater Seep
(immediately downgradient from
sampling location)
Burro Canyon Formation
Brushy Basin Member
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl H:/718000/hyrpt2022/figures/UflvectNchlQ21.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
30
saturated thickness estimated
to be less than 5 feet
KRIGED 4th QUARTER, 2021 WATER LEVELS
SHOWING KRIGED NITRATE AND CHLOROFORM PLUMES
AND GENERAL FLOW DIRECTIONS
WHITE MESA SITE
4th quarter, 2021 chloroform plume
4th quarter, 2021 nitrate plume
estimated perched water flow direction
SJS
H:\718000\hydrpt2022\TW27area_wl_4Q21.xls: plot F31
5510
5520
5530
5540
5550
5560
5570
5580
12/31/1999 12/30/2001 12/31/2003 12/30/2005 12/31/2007 12/30/2009 12/31/2011 12/30/2013 12/31/2015 12/30/2017 12/31/2019 12/30/2021
el
e
v
a
t
i
o
n

(
f
t

a
m
s
l
)
date
TW4-6 TW4-13 TW4-14
TW4-26 TW4-27
WATER LEVELS IN WELLS NEAR TW4-27HYDRO
GEO
CHEM, INC.Approved FigureDateAuthorDateFile Name
SJS 31plot F31SJS
HYDRO
GEO
CHEM, INC.
1 mile
WHITE MESA
Mill Site
CORRAL CANYON
CORRAL SPRINGS
COTTONWOOD
ENTRANCE SPRING
RUIN SPRING
WESTWATER
Cell 1
Cell 2
Cell 3
Cell 4A
Cell 4B
MW-01
MW-02
MW-3A
MW-11
MW-14MW-15
MW-17
MW-18
MW-19
MW-20
MW-21
MW-22
MW-23
MW-24
MW-25
MW-27
MW-28
MW-29
MW-30
MW-31
MW-32
MW-33
MW-34MW-37
MW-38
MW-39
MW-40
TW4-01
TW4-03
TW4-34
TWN-01
TWN-02
TWN-03
TWN-04
TWN-05
TWN-06
TWN-07
TWN-08
TWN-09
TWN-10
TWN-11 TWN-12
TWN-13
TWN-14
TWN-15
TWN-16
TWN-17
TWN-18
TWN-19
TWN-20
TWN-21
PIEZ-01
PIEZ-02
PIEZ-3A
PIEZ-04
PIEZ-05
TW4-05
TW4-12
TW4-13
TW4-31
TW4-32
MW-12
TW4-11TW4-16
TW4-18
TW4-27
MW-26
MW-35
MW-36
TW4-04
TW4-07
TW4-09
TW4-19
TW4-21
TW4-24
TW4-25
TW4-26
TW4-40
TW4-06
TW4-42
TW4-02
TW4-08
MW-04
MW-05
TW4-22
TW4-23
TW4-20
TW4-28
TW4-29
TW4-30
TW4-10
TW4-33
TW4-35
TW4-36
TW4-41TW4-14
DR-05 DR-06 DR-07
DR-08
DR-09
DR-10 DR-11 DR-12 DR-13
DR-14 DR-15
DR-17
DR-19 DR-20 DR-21
DR-22
DR-23
DR-24
TW4-37 TW4-38
TW4-39
MW-24A
abandoned abandoned
abandoned
abandoned
abandoned abandoned
abandoned
abandoned abandoned
abnd
AWN-X1
AWN-X2
AWN-X3
abnd
abnd
abnd
wildlife pond
wildlife pond
wildlife pond
TW4-43
DR-02
DR-16
DR-18
DR-25
abandoned
abandoned
abandoned
abandoned
EXPLANATION
seep or spring
RUIN SPRING
MW-30 perched boring showing pyrite in log and
having no laboratory detection
MW-29 perched boring having a possible pyrite
detection via laboratory analysis
(but not shown in log)
MW-24 perched boring having pyrite detected via
laboratory analysis only (not shown in log)
MW-25 perched boring showing pyrite in log and
having a laboratory detection (if analyzed)
MW-33 perched boring having detailed log
showing no pyrite
perched boring (pyrite status unknown)MW-5
WHITE MESA SITE PLAN
SHOWING PYRITE OCCURRENCE IN
PERCHED BORINGS
32H:/718000/hydrpt2022/
figures/pyrite_ocuurence21.srfSJS
(note: 'abnd' = abandoned)
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well
perched piezometer
seep or spring
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
temporary perched nitrate monitoring
well
TW4-12
TWN-7
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021
temporary perched monitoring
well installed September, 2021
TW4-43
TWN-20
saturated thickness estimated
to be less than 5 feet
5500
4th quarter 2021 water level
contour and label in feet amsl
PROPOSED NEW CELL 5A AND 5B
MONITORING WELLS AND PIEZOMETER
WHITE MESA SITE
H:/718000/hydrpt2022/
figures/UwlPropWellC5_r1.srf 33SJS
MW-42
DR-26

APPENDIX A

LITHOLOGIC LOGS

APPENDIX A.1

DR - SERIES

APPENDIX A.2

MW - SERIES

APPENDIX A.3

PIEZ - SERIES

APPENDIX A.4

TW4 - SERIES

APPENDIX A.5

TWN - SERIES

APPENDIX A.6

REVISED MANCOS PRESENCE AND THICKNESS
HYDRO
GEO
CHEM, INC.APPROVED DATE REFERENCE FIGURE
1 mile
CORRAL CANYON
CORRAL SPRINGS
COTTONWOOD
ENTRANCE SPRING
RUIN SPRING
WESTWATER
Cell 1
Cell 2
Cell 3
Cell 4A
Cell 4B
7.5
11
13 17
6
9.5
6
17.5
5
2 3
12
MW-3A
MW-23
MW-24 MW-28
MW-38
PIEZ-01
PIEZ-02
PIEZ-05
TWN-09
DR-02 DR-05
DR-09
MW-05
MW-11
MW-12
MW-14MW-15
abandoned
abandoned
EXPLANATION
seep or spring
RUIN SPRING
perched boring re-interpreted
to have Mancos Shale showing
estimated thickness in feet
MW-24
13
H:/718000/hydrpt2022/
report/AppA.6/newmancos_4Q21.srf
WHITE MESA SITE PLAN
SHOWING BORINGS RE-INTERPRETED
TO HAVE MANCOS SHALE
Mancos likely to have been present
prior to cell excavation/construction
MW-12
A.6SJS3/28/2022

APPENDIX B

WELL CONSTRUCTION SCHEMATICS

APPENDIX B.1

DR - SERIES

APPENDIX B.2

MW - SERIES

APPENDIX B.3

TW4 - SERIES

2
TW4-27
AS-BUILT WELL CONSTRUCTION SCHEMATIC
SJS 10/25/11 K:\7180272A Well Construction DiagramCHEM, INC.
GEO
HYDRO
Approved Date FigureReference
2
CHEM, INC.
GEO
HYDRO
Approved DateDate File Name FigureAuthor
TW4-43
AS-BUILT WELL CONSTRUCTION SCHEMATIC
SJS 9/28/21 7180291A 2JAA9/28/21

APPENDIX B.4

TWN - SERIES

CHEM, INC.
GEO
HYDRO
Approved DateDate File Name FigureAuthor
TWN-20
AS-BUILT WELL CONSTRUCTION SCHEMATIC
SJS 04/29/21 7180290A 2JAA04/29/21

CHEM, INC.
GEO
HYDRO
Approved DateDate File Name FigureAuthor
TWN-21
AS-BUILT WELL CONSTRUCTION SCHEMATIC
SJS 04/29/21 7180290A 3JAA04/29/21

APPENDIX C

INTERA SOIL BORING LOGS

H:\718000\hydrpt14\AppC_INTERA_logs\INTERA soil boring logs summary.doc
C-1
APPENDIX C
INTERA SOIL BORING LOGS SUMMARY

In May and June 2011, INTERA, Inc. installed 75 soil borings in the vicinity of the mill site.
Borings GP-01A1 through GP-02A1 and GP-01C through GP-07C were installed to the north
and south of the mill site and tailings cells; GP-01B through GP-48B were completed within and
immediately outside the area of the mill site. Borings were drilled by Earth Worx using the
Geoprobe push probe method. Soil samples for lithologic logging were collected using the
continuous dual tube method. Locations of soil borings are provided on Figures C.1 and C.2;
copies of the boring logs are provided in Appendix C.1.
Soil samples from the GP-A1 and GP-B series borings showed a consistent lithology. Depths of
refusal ranged from 2.7 ft bgs to 9.7 ft bgs. Yellowish-red, silty, fine sand predominated from the
ground surface to about four to six ft bgs, generally transitioning to pink, silty, fine sand or pink
sandstone to the depth of refusal. Roots were occasionally present in the top several feet of the
borings.
Soil samples from the GP-C series borings within or near the mill site showed more variable
lithology. Depths to refusal were deeper overall than in the GP-A1 and GP-B series borings, and
ranged from 1.7 to 24.5 ft bgs. Yellowish-red silty sand predominated in the upper portion of the
GP-C borings, from approximately four to 10 ft bgs, and was typically underlain by interbedded
reddish clay or clayey silt, and pinkish silt or silty sand to the depth of refusal. Gypsum
precipitate was commonly seen in the lower portions of the GP-C series borings, and fine gravel
was present in low proportions in multiple borings.

FIGURES
HYDRO
GEO
CHEM, INC.
APPROVED DATE REFERENCE FIGURE
1 mile
Mill Site
CORRAL CANYON
CORRAL SPRINGS
COTTONWOOD
ENTRANCE SPRING
RUIN SPRING
WESTWATER
Cell 1
Cell 2
Cell 3
Cell 4A
Cell 4B
GP-01A
GP-02A
GP-03A
GP-04A
GP-05A
GP-06A
GP-07A
GP-08A
GP-09A
GP-10A
GP-11A
GP-12A
GP-13A
GP-14A
GP-15A
GP-16A
GP-17A
GP-18A
GP-19A GP-20A
GP-01C
GP-02C
GP-03C
GP-04C
GP-05C
GP-06C GP-07C
EXPLANATION
off-site Intera soil borings
GP-01A through GP-20A
seep or spring
GP-01A
RUIN SPRING
off-site Intera soil borings
GP-01C through GP-07C
GP-01C
GP-01B on-site Intera soil borings
GP-01B through GP-48B
INTERA SOIL BORING LOCATIONS
WHITE MESA SITE
See Inset Map Detail
Figure C.2
H:/718000/hydrpt14/Intera_logs/interaloc.srf C.1
Cell 1
Cell 2
Cell 3
Cell 4A
GP-07B
GP-35B
GP-25B
GP-39B
GP-08B
GP-36B
GP-44B
GP-26B
GP-40B
GP-11BGP-12B
GP-31B
GP-32B
GP-33B
GP-46B
GP-47B
GP-42B
GP-43B
GP-21BGP-22B
GP-23B
GP-24B
GP-16B
GP-37B
GP-03B
GP-05B GP-10B
GP-34B
GP-45B
GP-48B
GP-41B
GP-15B
GP-38B
GP-04B
GP-01B
GP-02B
GP-09B
HYDRO
GEO
CHEM, INC.APPROVED DATE REFERENCE FIGURE
EXPLANATION
GP-01B
INTERA BORING LOCATIONS
GP-1B THROUGH GP-48B
(DETAIL MAP)
WHITE MESA SITEon-site Intera soil
borings GP-01B
through GP-48B
GP-06B
GP-13B
GP-14B
GP-30BGP-28BGP-27B
GP-29B
GP-20B
GP-19B
GP-17B GP-18B
H:/718000/hydrpt14/
Intera_logs/intera_loc_det_rev.srf C.2

APPENDIX C.1
INTERA SOIL BORING LOGS
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
1
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-01A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.95
0.5/0.65
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.7' Silty SAND, reddish brown (5YR 4/4), very fine-grained sand, silt, poorly graded, very loose, dry, little white mottling, HCl strong
3.7-4.5' Silty SAND, pink (5YR 6/4), very fine-grained sand, silt, poorly graded, medium dense, dry, HCl strong
Total depth of boring 4.5' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
2
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-02A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
3.1/3.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.7' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl weak to moderate, little white mottling w/ HCl strong
4.7-7.1' Silty SAND, pink (5YR 7/3), very fine-grained sand, silt, poorly graded, dense, dry, HCl strong,
trace fine sand
Total depth of boring 7.1' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
3
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-03A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
2.8/3.1
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis (1)
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose, dry, root at top, HCl strong
4.0-6.8' Silty SAND, reddish yellow (6/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl strong, trace fine sand
Total depth of boring 6.8' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
4
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-04A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.7' Silty SAND, reddish brown (5YR 4/4), very fine-grained sand, silt, poorly graded, very loose, dry, little white mottling, HCl strong
3.7-4.0' Silty SAND, pink (5YR 6/4), very fine-grained sand, silt, poorly graded, medium dense, dry, HCl strong
Total depth of boring 4.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
5
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-05A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Duel Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.7
3.6/3.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-6.4' Silty SAND, yellow red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose, roots at top, HCl moderate
6.4-7.6' Silty SAND, light brown gray (10YR 6/2), very fine-grained sand, silt, poorly graded, dense, dry, HCl strong, trace fine sand
Total depth of boring 7.6' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
6
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-06A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.1
4.0/3.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis (1)
0-5.9' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl moderate, trace roots at top, little white mottling w/ HCl strong
5.9-8.0' Silty SAND, very pale brown (10YR 8/4), very fine-grained sand, silt, poorly graded, dense, dry,
HCl strong, trace fine sand
Total depth of boring 8.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
7
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-07A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
4.0/3.3
1.7/1.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.9' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl strong, little white mottling, HCl strong 4 to 4.9' bgs
4.9-7.5' Silty SAND, pink (7.5YR 7/4), very fine-grained sand, silt, poorly graded, medium dense to
dense, dry, HCl strong, trace loose fine sand 7 to 7.5'
7.5-9.7' Silty SAND, pink (7.5YR 7/3), very fine-grained sand, silt, poorly graded, loose to dense, dry, HCl
strong, trace fine sand
Total depth of boring 9.7' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
8
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-08A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.5' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose, dry, trace gravel, roots at top, HCl none
3.5-4.0' Silty SAND, pink (7.5YR 8/4), very fine-grained sand, silt, poorly graded, dense, dry, HCl strong
Total depth of boring 4.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
9
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Duplicate sample collected. Sample interval was increased to 2 feet to
accommodate additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-09A1
(Page 1 of 1)
Date/Time Started : 05/17/11
Date/Time Completed : 05/17/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.95
4.0/3.75
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose, dry, HCl none, trace roots
4.0-8.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand trace fine-grained sand, silt, poorly graded, loose, HCl none, trace mica, trace white mottled w/ HCl strong
Total depth of boring 8.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
0
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-10A1
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
2.66/1.25
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none to weak
2.0-2.7' Sand/Silty Sand, very pale brown (10YR 8/3), very fine-grained sand, trace silt, poorly graded,
loose, dry, subangular to subrounded, HCl none, little very fine sand
Total depth of boring 2.7' bgs (refusal)
US
C
S
SM
SP/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
1
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Duplicate sample collected. Sample interval was increased to 2 feet to
accommodate additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-11A1
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
1.0/1.2
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none
3.0-5.0' Silty SAND, yellowish red (5YR 5/8 & very pale brown 10YR 8/2), fine-grained sand, silt, poorly
graded, loose to medium dense, dry, some white mottling w/ HCl strong, mottled but little red or very pale
brown, HCl weak to medium, trace fine sand
Total depth of boring 5.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
2
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-12A1
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none
2.0-4.0' Silty SAND, pink (5YR 7/4), very fine-grained sand, silt, poorly graded, medium dense loose to
medium dense, trace fine sand, dry, some white mottling w/ HCl strong
Total depth of boring 4.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
3
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-13A1
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.1
0.7/0.7
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, trace white mottling w/ HCl strong
4.0-4.7' Silty SAND, pink (5YR 7/4), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl strong, trace fine sand
Total depth of boring 4.7' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
4
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-14A1
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.9
2.9/1.9
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-5.8' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, trace white mottling w/ HCl strong, HCl none to weak
5.8-6.9' Silty SAND, pink (5YR 7/4 & yellowish red 5YR 5/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, some what mottling w/ HCl strong, trace fine sand
Total depth of boring 6.9' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
5
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-15A1
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
3.6/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-5.1' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, trace white mottling w/ HCl strong, HCl none to weak
5.1-7.6' Silty SAND, pink (5YR 7/4), very fine-grained sand, silt, poorly graded, medium dense, dry, trace
fine sand, HCl strong, some white mottling w/ HCl strong
Total depth of boring 7.6' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
6
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Duplicate sample collected. Sample interval was increased to 2 feet to
accommodate additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-16A1
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.7
3.1/3.3
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.1' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none
3.1-7.1' Silty SAND, pink (5YR 7/4), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl strong, trace fine sand
Total depth of boring 7.1' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
7
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Notes:
Log of Soil Boring GP-17A1
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
3.2/2.9
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2.5' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl weak
2.5-3.2' Silty SAND, pink (5YR 7/4), very fine-grainded sand, silt, loose to medium dense, dry, HCl strong, trace fine sand, little white mottling w/ HCl strong
Total depth of boring 3.2' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
8
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Notes:
Log of Soil Boring GP-18A1
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
3.3/3.1
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-6.9' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl strong, trace white mottling w/ HCl strong, trace roots at top
6.9-7.3' Silty SAND, pink (5YR 7/4), very fine-grainded sand, silt, poorly graded, loose to medium dense,
dry, HCl strong, trace fine sand
Total depth of boring 7.3' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
9
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Duplicate sample collected. Sample interval was increased to 2 feet to
accommodate additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-19A1
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.9
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-6.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none to weak, little white mottling w/ HCl strong
6.0-8.0' Silty SAND, pink (5YR 7/4), very fine-grainded sand, silt, poorly graded, loose to medium dense, dry, HCl strong, trace fine sand, sand & fine gravel 7.9-8.0' bgs
Total depth of boring 8.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
re
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
0
A
1
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Notes:
Log of Soil Boring GP-20A1
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
1.1/1.3
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.1' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none
3.1-5.1' Silty SAND, pink (5YR 7/4), very fine-grainded sand, silt, loose to medium dense, dry, HCl weak to strong, little white mottling w/ HCl strong, trace fine sand
Total depth of boring 5.1' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
1
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-01B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.15
0.4/0.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.1' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, loose to dense, dry, HCl strong, mottling common
3.1-4.4' Silty Gravelly SAND, pinkish gray (5YR 7/2), very fine- to coarse-grained sand (~60%), gravel to 0.1" diameter (~30%), well graded, angular to subrounded, very loose, non-plastic, dry, no HCl
Total depth of boring 4.4' bgs (refusal)
US
C
S
SM
SW/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
2
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-02B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/1.5
4.0/3.8
3.8/3.5
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~65%), poorly graded, subangular to subrounded, loose, dry, HCl strong, roots abundant top 0.5'
3.0-7.0' Lean CLAY, light reddish brown (5YR 6/3), very fine-grained sand (~25%), subangular to
subrounded, soft, medium plastic, moist, HCl moderate
7.0-11.8' Clayey SAND, light reddish brown (5YR 6/3), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose to dense, medium plastic, moist, HCl strong
Total depth of boring 11.8' bgs (refusal)
US
C
S
SM
CL
SC
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
3
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-03B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
4.0/4.0
1.6/2.2
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~80%), poorly graded, subangular to subrounded, loose, dry, HCl strong, mottling common
4.0-8.6' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded, subangular
to subrounded, loose, moist, HCl strong, mottling common
8.6-9.6' Lean CLAY, pink (5YR 7/4), very fine-grained sand (~25%), subangular to subrounded, soft, moderately plastic, moist, HCl strong
Total depth of boring 9.6' bgs (refusal)
US
C
S
SM
CL
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
4
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-04B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
0.8/1.1
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, loose, dry, HCl weak, mottling common, roots in top 0.3'
4.0-4.6' SILT, red (2.5YR 5/6), very fine-grained sand (~25%), loose, non-plastic, non-cohesive, dry, HCl
strong
Total depth of boring 4.8' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
5
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-05B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
4.0/3.4
4.0/3.9
1.3/1.3
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-6.5' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, loose, dry, HCl strong, white mottling common, roots in top 1.3'
6.5-13.3' Clayey SILT, yellowish brown (10YR 5/4), loose to dense, non- to slightly plastic, dry to moist, HCl slight, gypsum stringers and precipitate common
Total depth of boring 13.3' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
6
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-06B
(Page 1 of 1)
Date/Time Started : 06/07/11
Date/Time Completed : 06/07/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
4.0/4.0
4.0/4.0
1.8/1.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~80%), poorly graded, angular to subrounded, very loose, dry, no HCl
1-4' HCl strong and 5YR 4/4
4.0-8.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~80%), poorly graded, angular to
subrounded, very loose, dry, HCl
8.0-12' Clayey SILT, yellowish brown (10YR 5/4), poorly graded, loose, non-plastic, dry to moist, HCl slight
12-13.8' Clayey SILT, yellowish brown (10YR 5/4), poorly graded, loose, non-plastic, dry, HCl slight, laminated
Total depth of boring 13.8' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
7
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to
accommodate for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-07B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.5
4.0/3.5
2.8/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, loose, dry, HCl strong, white mottling common
4.0-8.0' Silty SAND, reddish brown (5YR 5/4), very fine-grainded sand (~80%), poorly graded,
subangular to subrounded, loose, dry, HCl strong, white mottling common
8.0-10.2' Silty SAND, reddish brown (5YR 5/4), very fine-grainded sand (~60%), poorly graded, subangular to subrounded, slightly dense, dry, HCl strong, white mottling common
10.2-10.8' SILT, pink (5YR 7/4), very dense to hard, non-plastic, dry, HCl strong
Total depth of boring 10.8' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
8
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-08B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
4.0/3.9
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
Road base
0.8-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~80%), poorly graded, subangular
to subrounded, dense, dry, HCl strong, white mottling throughout
4.0-8.0' SILT, pink (5YR 7/4), trace very fine-grained sand, loose, non-plastic, dry, HCl strong
8.0-11.3' Silty SAND, pink (5YR 7/4), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose to dense, dry, HCl strong
11.3-12' SILT, pink (5YR 7/4), very dense, hard, non-plastic, dry, HCl strong
Total depth of boring 12' bgs (refusal)
US
C
S
SM
ML
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
9
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-09B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.2
4.0/3.75
3.4/3.4
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, reddish brown (5YR 5/4), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, dry, HCl strong, white mottling common
4.0-8.0' Silty SAND, reddish brown (5YR 5/4), very fine-grained sand (~80%), poorly graded,
subangular to subrounded, loose, dry, HCl strong, white mottling common
8.0-10.8' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, slightly dense, dry to moist, HCl strong, white mottling common
10.8-11.4' SILT, pink (5YR 7/4), very dense, hard, non-plastic, dry, HCl strong
Total depth of boring 11.4' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
0
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-10B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
4.0/4.0
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, dry, HCl strong, white mottling common
4.0-8.0' Silty SAND, reddish brown (5YR 5/4), very fine-grained sand (~60%), poorly graded,
subangular to subrounded, loose, dry, HCl strong, white mottling common
8.0-11.5' Silty SAND, reddish brown (5YR 5/4), very fine-grained sand (~60%), poorly graded, loose to dense, dry, HCl strong, white mottling common
11.5- 12' SILT, pink (5YR 7/4), very dense, hard, dry, HCl strong
Total depth of boring 12' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
1
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-11B
(Page 1 of 1)
Date/Time Started : 06/07/11
Date/Time Completed : 06/07/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
4.0/3.2
4.0/3.2
0.1/0.1
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2.0' Silty SAND, reddish brown (5YR 4/4), very fine-grained sand (~60%), poorly graded, subangular to subrounded, very loose, dry, HCl slight, roots
2.0-4.0' Silty SAND, light reddish brown (5YR 6/3), very fine-grained sand (~60%), poorly graded,
subangular to subrounded, very loose, dry, HCl strong
4.0-7.0' Silty SAND, light reddish brown (5YR 6/3), very fine-grained sand (~60%), poorly graded,
subangular to subrounded, very loose, dry, HCl strong
7.0-12.1' Clayey SILT, pinkish gray (7.5YR 6/2), loose to dense, non-plastic, dry, HCl strong, white mottling common, laminated
Total depth of boring 12.1' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
2
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-12B
(Page 1 of 1)
Date/Time Started : 06/07/11
Date/Time Completed : 06/07/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.5
4.0/3.1
4.0/3.4
0.4/0.4
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.5' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, poorly graded, subangular to subrounded, very loose, dry, no HCl 0-1.5' bgs, HCl slight
1.5-8.0' Silty SAND, reddish brown (5YR 5/4), very fine-grained sand, poorly graded, subangular to
subrounded, very loose, dry, HCl slight, laminated
8.0-12.4' Clayey SILT, light olive brown (2.5YR 4/3), poorly graded, loose, non-plastic, dry, HCl, laminated, gypsum precipitate throughout
10.5-12' 5-10mm gypsum stringers
Total depth of boring 12.4' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
3
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-13B
(Page 1 of 1)
Date/Time Started : 06/07/11
Date/Time Completed : 06/07/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
4.0/4.0
4.0/4.0
1.8/1.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.5' Silty SAND, yellowish red brown (5YR 4/6), very fine-grained sand, poorly graded, subangular to subrounded, very loose, dry, HCl slight
1.5-6.2' Silty SAND, light reddish brown (5YR 6/3), very fine-grained sand, poorly graded, subangular to
subrounded, very loose, dry, HCl slight
6.2-8.0' Clayey SILT, reddish brown (5YR 5/4), trace very fine-grained sand, loose to dense,
non-plastic, dry to moist, HCl strong, white mottling throughout
8.0-12' Clayey SILT, dark grayish brown (10YR 4/2), dense, slightly plastic, dry, HCl weak, thin bedding
12-13.8' Clayey SILT, light yellowish brown (10YR 6/4), loose, non-plastic, dry, HCl slight, thin bedding
Total depth of boring 13.8' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
4
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-14B
(Page 1 of 1)
Date/Time Started : 06/07/11
Date/Time Completed : 06/07/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
4.0/3.0
4.0/3.5
2.0/2.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand, poorly graded, subangular to subrounded, very loose, dry, no HCl
quartz fragments 4.0-4.7' bgs
4.7-8.0' Silty SAND, reddish yellow (2.5YR 6/6), very fine-grained sand, poorly graded, loose to dense,
dry, HCl moderate, white mottling throughout
8.0-12' Clayey SILT, brown (7.5YR 5/2), poorly graded, loose to dense, non-plastic, dry, HCl slight
12-14' Clayey SILT, yellowish brown (10YR 5/6), poorly graded, loose to dense, non-plastic, dry, HCl slight
Total depth of boring 14' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
5
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-15B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.4
4.0/3.4
4.0/2.8
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.5' Silty SAND, yellowish red (5YR 4/6), very fine- to medium-grained sand (~80%), well graded, angular to subrounded, loose, dry to moist, HCl moderate, minor white mottling
3.5-4.0' Clayey SILT, light reddish brown (5YR 6/4), poorly graded, dense, slightly plastic, moist, HCl
moderate
4.0-10' Silty SAND, yellowish red (5YR 4/6), very fine-grainded sand (~75%), poorly graded, subangular
to subrounded, loose, dry to moist, HCl strong, white mottling throughout
10-12' CLAY, yellowish red (5YR 4/6), dense, low to medium plastic, cohesive, moist, HCl slight
12-16' CLAY, pale brown (10YR 6/3), very dense, low plastic, slightly cohesive, dry, HCL moderate, minor FeO staining
Total depth of boring 16' bgs (refusal)
US
C
S
SM
ML/CL
SM
CL
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
6
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-16B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
4.0/3.2
4.0/3.1
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-5.5' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~75%), poorly graded, subangular to subrounded, loose, dry to moist, no HCl
5.5-8.0' Silty SAND, reddish yellow (5YR 6/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, dry, HCl strong, white mottling throughout
8.0-11.3' CLAY, reddish yellow (5YR 6/6), hard, medium plastic, cohesive, dry to moist w/ increasing
moisture towards base of interval, HCl strong
11.3-16' CLAY, pale brown (10YR 6/3), very hard, slightly plastic, slightly cohesive, moist, HCl strong
Total depth of boring 16' bgs (refusal)
US
C
S
SM
CL
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
7
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-17B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
4.0/3.85
4.0/3.65
4.0/3.4
2.6/2.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.4' FILL
1.4-12' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~75%), poorly graded, subangular to subrounded, loose, dry, HCl moderate, white mottling common
12-15.6' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, moist, HCl strong, white mottling common
15.6-16' SILT, very pale brown (10YR 7/4), hard, non-plastic, non-cohesive, dry, HCl moderate
16-18' Lean CLAY, yellowish red (5YR 5/6), very fine-grained sand (~30%), subrounded, soft, slightly plastic, slightly cohesive, moist, HCl slight
18-18.6' SILT, very pale brown (10YR 7/4), hard, non-plastic, non-cohesive, dry, HCl moderate
Total Depth of Boring 18.6' bgs (refusal)
US
C
S
SM
ML
ML/CL
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
8
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-18B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/4.0
4.0/3.8
4.0/3.8
4.0/3.25
2.5/2.85
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.5' FILL
1.5-12' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~75%), poorly graded, subangular
to subrounded, loose, dry, HCl strong, white mottling common, caliche rich 10-10.5' bgs
12-16' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~75%), poorly graded, subangular to subrounded, loose, slightly moist with moisture increasing w/ depth, HCl strong, occasional white mottling
16-17.9' Sandy Silty CLAY, yellowish red (5YR 5/6), very fine-grained sand (~30%), soft, slightly plastic, slightly cohesive, moist, HCl slight
17.9-18.5' SILT, very pale brown (10YR 7/4), hard, non-plastic, non-cohesive, dry, HCl strong, shale
Total depth of boring 18.5' bgs (refusal)
US
C
S
SM
ML/CL
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
1
9
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-19B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.85
4.0/3.85
4.0/3.95
4.0/3.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2.5' FILL
2.5-12' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~75%), poorly graded, subangular to subrounded, loose, dry, HCl moderate, occasional white mottling
12-17.1' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose to dense, slightly moist to moist increasing w/ depth, HCl strong, occasional white mottling
17.1-17.9' SILT, very pale brown (10YR 7/4), very dense, hard, non-plastic, dry, HCl strong, weathered
shale
Total depth of boring 17.9' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
0
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-20B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/4.0
4.0/3.9
4.0/3.5
4.0/3.2
1.4/1.4
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.0' FILL
1.0-12' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, loose, dry, HCl moderate, occasional white mottling
12-16' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, moist, HCl moderate, occasional white mottling
16-16.7' Sandy Lean CLAY, very fine-grained sand (~15%), yellowish red (5YR 5/6), soft, medium plastic, medium cohesive, very moist, HCl slight
16.7-17.4' SILT, very pale brown (10YR 7/4), hard, non-plastic, dry, HCl strong, shale
Total depth of boring 17.4' bgs (refusal)
US
C
S
SM
CL
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
1
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-21B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.3
2.7/2.9
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.5' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, loose, moist, HCl weak, gravel from 3.8-4.0'
4.5-5.5' Silty SAND, pink (5YR 7/3), very fine-grained sand (~60%), poorly graded, subrounded, loose,
slightly cohesive, wet, HCl moderate
5.5-6.7' Sandy SILT, light yellowish brown (10YR 6/4), very fine-grained sand (~15%), poorly graded,
subrounded, loose, dry, thin bedding, HCl strong
Total depth of boring 6.7' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
2
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-22B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
4.0/2.9
0.9/1.9
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~75%), poorly graded, subrounded, loose, dry to slightly moist, HCl no to weak
4.0-7.6' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded,
subrounded, loose, moist to very moist, HCl weak
7.6-8.0' SILT, pink (5YR 8/3), very fine-grained sand (~25%), poorly graded, subrounded, dense, slightly cohesive, moist, HCl strong8.0-8.9' SILT, brownish yellow (10YR 6/6), very fine-grained sand (~25%), poorly graded, subrounded,
loose, slightly moist, HCl weak, thin bedding
Total depth of boring 8.9' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
3
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-23B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
4.0/2.5
4.0/2.0
3.3/2.3
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2.0' Silty SAND, reddish gray (5YR 5/2), very fine- to coarse-grained sand, well graded, angular to subrounded, loose, non-plastic, dry, HCl moderate
2.0-4.0' Lean CLAY w/ Sand, brownish yellow (10YR 6/6), fine- to coarse-grained sand (~20%), well
graded, angular to subrounded, hard, slightly plastic, moist, HCl slight, burned (ash?) layer from 2.0-2.2'
bgs
4.0-15.3' Sandy Lean CLAY, reddish brown (5YR 5/4), fine- to coarse-grained sand (~30%), up to 0.05'
diameter gravel (<10%), well graded, angular to subrounded, soft, low to moderate plastic, moist, HCl
weak
Total depth of boring 15.3' bgs (refusal)
US
C
S
SW/SM
CL
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
4
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-24B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.7
4.0/2.7
4.0/2.5
0.8/0.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-8.0' Clayey Gravelly SAND, dark yellowish brown, (10YR 4/4), very fine- to coarse-grained sand (~75%), up to 0.04' diameter gravel (~15%), soft, slightly plastic, moist, HCl weak
8.0-11.3' Sandy Gravelly SILT, brown (10YR 5/3), fine- to coarse-grained sand (~30%), up to 0.02'
diameter gravel (~10%), soft, slightly plastic, moist, HCl weak
11.3-12.5' Silty SAND, brownish yellow (10YR 6/6), very fine- to fine-grained sand (~70%), well graded,
subangular to subrounded, dense, dry, no HCl, gypsum precipitate throughout
12.5-12.8' Silty SAND, yellowish red (5YR 4/6), very fine- to fine-grained sand (~80%), poorly graded, subangular to subrounded, loose, wet, HCl weak
Total depth of boring 12.8' bgs (refusal)
US
C
S
SW/SC
ML
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
5
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-25B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.1
4.0/3.6
4.0/3.8
4.0/4.0
3.4/3.4
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-0.75' Road base gravel
0.75-11.7' Silty SAND, reddish yellow (5YR 6/6), very fine-grained sand (~65%), poorly graded,
subangular to subrounded, loose to dense, dry to 10.9' bgs, moist to 11.7' bgs, HCl strong, occasional
white mottling
11.7-13.3' CLAY, reddish yellow (5YR 6/6), dense, plastic to very plastic, cohesive, slightly moist, HCl strong
13.3-19.4' CLAY, pale brown (10YR 6/3), dense, slightly plastic, slightly cohesive, dry, HCl slight, weathered shale, platy shale fragments increasing w/ depth, weathered shale w/ shale fragments
Total depth of boring 19.4' bgs (refusal)
US
C
S
SM
CL/CH
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
6
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-26B
(Page 1 of 1)
Date/Time Started : 06/09/11
Date/Time Completed : 06/09/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
4.0/3.3
4.0/3.6
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-0.3' Road base gravel
0.3-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, dense, moist, HCl strong, white mottling common
4.0-10.1' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~80%), poorly graded,
subangular to subrounded, dense, dry to moist, HCl moderate, white mottling common
10.1-13' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, subangular
to subrounded, dense, moist, HCl moderate
13-16' SILT, yellowish brown (10YR 5/4), very dense, hard, dry, HCl strong
Total depth of boring 16' bgs (refusal)
US
C
S
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
7
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-27B
(Page 1 of 1)
Date/Time Started : 06/10/11
Date/Time Completed : 06/10/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
4.0/3.3
4.0/3.6
2.6/2.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~80%), poorly graded, subangular to subrounded, loose, dry, HCl moderate, mottling common
4.0-11.8' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~70%), poorly graded,
subangular to subrounded, loose, moist, HCl weak, mottling rare
11.8-13' Clayey SAND, yellowish red (5YR 4/6), very fine-grained sand, subrounded, loose, slightly
plastic, moist, HCl strong, mottling throughout
13-14.6' Sandy SILT, yellowish brown (10YR 5/6), very fine-grained sand (~25%), subrounded, loose,
non-plastic, non-cohesive, dry, HCl strong
Total depth of boring 14.6' bgs (refusal)
US
C
S
SM
SC
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
8
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-28B
(Page 1 of 1)
Date/Time Started : 06/10/11
Date/Time Completed : 06/10/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
4.0/3.0
4.3/3.4
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-7.4' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, moist, HCl weak to strong
7.4-7.7' Lean CLAY w/ Sand, very dark gray (5YR 3/1), very fine-grained sand (~15%), soft, plastic, moist, HCl weak
7.7-12' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~80%), poorly graded, subangular to subrounded, loose, moist, HCl weak, occasional mottling
12-12.3' Clayey SAND, very pale brown (10YR 7/3), very fine-grained sand w/ plastic fines, poorly graded, subangular to subrounded, loose, slightly plastic, moist, HCl strong
Total depth of boring 12.3' bgs (refusal)
US
C
S
SM
CL
SM
SC
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
2
9
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-29B
(Page 1 of 1)
Date/Time Started : 06/10/11
Date/Time Completed : 06/10/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.95
4.0/3.0
4.0/3.25
2.4/2.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.3' Road base
1.3-3.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~80%), poorly graded, subangular to subrounded, loose, dry, HCl moderate, white mottling throughout
3.0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~80%), poorly graded, subangular to subrounded, loose, moist, gravel and wood fragments common, HCl moderate,
4.0-12' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, subangular
to subrounded, loose, dry to moist, HCl weak, occasional mottling
12-13.2' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, moist, HCl moderate
13.2-14.4' Silty SAND, yellowish brown (10YR 5/4), very fine-grained sand (~60%), poorly graded, subangular to subrounded, dense, moist, HCl moderate
Total depth of boring 14.4' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
0
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-30B
(Page 1 of 1)
Date/Time Started : 06/10/11
Date/Time Completed : 06/10/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
4.0/3.15
4.0/3.3
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-7.1' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, loose, dry to moist, HCl weak, occasional mottling
7.1-7.2' Clayey SAND w/ low plastic fines, dark reddish brown (5YR 3/4), very fine-grained sand, poorly graded, subrounded, soft, slightly plastic, moist, HCl moderate
7.2-12' Silty SAND, Yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded,
subrounded, loose, moist, HCl none to weak
12-13.1' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subrounded, loose, wet, HCl moderate
Total depth of boring 13.1' bgs (refusal)
US
C
S
SM
SC
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
1
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-31B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.1
1.6/1.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.7' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~65%), poorly graded, subangular to subrounded, very loose, dry, HCl moderate, white mottling throughout
4.7-5.6' SAND w/ minor Silt, pinkish gray (7.5YR 6/2), very fine- to fine-grained sand, poorly to well
graded, subangular to subrounded, very loose, moist, HCl strong
Total depth of boring 5.6' bgs (refusal)
US
C
S
SM
SP/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
2
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-32B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.9
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subangular to subrounded, very loose, dry to moist increasing w/ depth, HCl moderate
Total depth of boring 4.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
3
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-33B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
1
2
3
4
5
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
1.7/1.7
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.2' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~75%), poorly graded, subangular to subrounded, very loose, dry, HCl moderate, minor white mottling
1.2-1.7' SAND w/ minor Silt, pinkish gray (5YR 6/2), very fine- to fine-grained sand, poorly to well
graded, subangular to subrounded, very loose, dry, HCl strong
Total depth of boring 1.7' bgs (refusal)
US
C
S
SM
SP/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
4
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-34B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
3.8/2.7
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~65%), poorly graded, subangular to subrounded, loose, dry to moist, HCl slight, minor roots 0-0.8' bgs
3.0-3.8' SAND w/ minor silt, pinkish gray (5YR 6/2), very fine- to fine-grained sand, poorly to well
graded, subangular to subrounded, very loose, moist, HCl strong
Total depth of boring 3.8' bgs (refusal)
US
C
S
SM
SP/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
5
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-35B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.5
4.0/1.8
4.0/2.7
4.0/3.7
2.9/2.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' SAND w/ gravel FILL, dark reddish brown (5YR 3/3), fine- to coarse-grained sand, gravel to 0.06' diameter, well graded, angular to subrounded, loose, dry, HCl moderate
4.0-11' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~75%), poorly graded, subrounded,
loose, moist, HCl moderate, mottling common
11-12' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~75%), poorly graded, subrounded,
dense, moist, HCl weak
12-17.4' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~75%), poorly graded, subrounded, loose, moist to wet near bottom of interval. HCl weak
17.4-18.9' Clayey SILT, yellowish brown (10YR 5/4), dense, slightly plastic, moist, HCl strong
Total depth of boring 18.9' bgs (refusal)
US
C
S
SW
SM
ML/CL
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
6
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-36B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.5
4.0/2.6
4.0/2.8
4.0/3.4
9.3/3.1
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2.5' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, loose, dry, HCl moderate, mottling common
2.5-11' Clayey Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subrounded, loose, soft, slightly plastic, moist, HCl moderate
11- 13' Clayey Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded,
subrounded, dense, slightly plastic, moist, no HCl
13-18.3' Silty SAND, reddish yellow ( 5YR 6/8), very fine-grained sand (~70%), poorly graded,
subrounded, loose, dry to moist increasing with depth, HCl strong, mottling common
18.3-19.3' SILT, light gray (10YR 7/2), very fine-grained sand (~30%), subrounded, dense, non-plastic,
dry, HCl strong, FeO staining
Total depth of boring 19.3' bgs (refusal)
US
C
S
SM
SM/SC
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
7
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-37B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
4.0/3.2
4.0/4.0
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded, subrounded, loose, dry, HCl strong, mottling throughout
4.0-9.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded,
subrounded, loose, moist, HCl slight, occasional mottling
9.0'-13.2' Clayey SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded,
subrounded, soft, slightly plastic, moist, HCl strong, ~30% motttling
13.2-16' Clayey SILT, yellowish brown (10YR 5/6), soft to hard, slightly plastic, moist, HCl strong, ~5% mottling
Total depth of boring 16' bgs (refusal)
US
C
S
SM
SC
ML/CL
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
8
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-38B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
4.0/3.3
4.0/3.1
4.0/4.0
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-5.0' Silty SAND, yellowish red (5YR 5/8), very fine-grained sand (~70%), poorly graded, subrounded, loose, dry, HCL strong, mottling common
5.0-11.9' Silty SAND, yellowish red (5YR 5/8), very fine-grained sand (~60%), poorly graded, subrounded, dense, moist, HCl weak
11.9-16' Clayey SILT, yellowish brown (10YR 5/6), soft to hard, slightly plastic, moist, massive-transitions to platy structure near bottom of interval, HCl slight
Total depth of boring 16' bgs (refusal)
US
C
S
SM
ML/CL
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
3
9
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-39B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
4.0/4.0
4.0/4.0
2.2/3.4
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-6.6' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~70%), poorly graded, subrounded, loose, dry to moist, HCL none 0-4' bgs & strong 4-6.6' bgs, mottling common 4-6.6' bgs
6.6-11' Lean CLAY, reddish brown (5YR 5/3), very fine-grained sand (~15%), poorly graded, subrounded soft, slightly plastic to plastic, moist, HCl strong
11-12.8' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded,
subrounded, loose, moist w/ moisture increasing with depth, HCl weak
12.8-14.2' Sandy SILT, gray (10YR 5/1), very fine-grained sand (~30%), poorly graded, subrounded, dense, dry, HCl weak, thin bedding to platy, FeO common 12.8-13.6' bgs
Total depth of boring 14.2' bgs (refusal)
US
C
S
SM
CL
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
0
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-40B
(Page 1 of 1)
Date/Time Started : 06/12/11
Date/Time Completed : 06/12/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
4.0/4.0
4.0/3.9
1.6/1.8
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, subrounded, loose, dry to moist, HCL moderate
4.0-8.0' Sandy Silty Lean CLAY, yellowish red (5YR 5/6), very fine-grained sand (~20%), poorly graded,
subrounded, soft, slightly plastic, moist, HCl moderate, occasional mottling
8.0-13' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~60%), poorly graded, subrounded,
loose, moist, HCl moderate, occasional mottling
13-13.6' Sandy SILT, yellowish brown (10YR 5/4), very fine-grained sand (~30%), poorly graded,
subrounded, soft, slightly plastic, moist, HCl moderate
Total depth of boring 13.6' bgs (refusal)
US
C
S
SM
ML/CL
SM
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
1
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-41B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
25
30
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.4
4.0/2.8
4.0/3.0
4.0/2.8
4.0/2.7
4.0/3.8
0.5/0.9
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-6.5' SAND, pale yellow (5Y 8/2), very fine- to fine-grained sand (~85%), poorly graded, subangular to subrounded, dense, dry, HCl none
6.5-19' Silty SAND, light brown (7.5YR 6/3) to pinkish gray (7.5YR 7/2), very fine-grained sand (~60%), poorly graded, subangular to subrounded, loose, dry, HCl none, thin bedded, occasional sandstone fragments, occasional FeO stains
19-24.5' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subrounded, loose, dry, HCl strong, mottling common
Total depth of boring 24.5' bgs (refusal)
US
C
S
SP
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
2
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-42B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.4
4.0/3.8
0.5/1.1
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-5.5' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~65%), poorly graded, subangular to subrounded, loose, dry to moist, HCl strong, mottling common
5.5-8.0' Clayey Silty SAND, reddish brown (5YR 5/4), very fine-grained sand, poorly graded,
subrounded, dense, slightly plastic, moist, HCl strong, mottling common
8.0-8.5' Silty CLAY, dark reddish brown (5YR 3/2), soft, slightly plastic to plastic, non-cohesive, dry, HCl strong, weathered shale, thin bedding
Total depth of boring 8.5' bgs (refusal)
US
C
S
SM
SM/SC
ML/CL
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
3
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-43B
(Page 1 of 1)
Date/Time Started : 06/11/11
Date/Time Completed : 06/11/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.5
4.0/4.0
1.7/1.9
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-1.8' Fill
1.8-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~65%), poorly graded,
subrounded, loose, dry, HCl moderate
4.0-5.8' Well Graded GRAVEL, very pale brown (10YR 2/3), fine- to medium-grained sand (~10%),
gravel (~40%), well graded, subangular to subrounded, very loose, non-plastic, dry, HCl moderate
5.8-8.4' Clayey SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded, subrounded, dense, plastic, moist, HCl strong
8.4-9.7' SILT, light yellowish brown (10YR 6/4), soft, non-plastic, non-cohesive, moist, HCl strong
Total depth of boring 9.7' bgs (refusal)
US
C
S
SM
GW/GM
SC
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
4
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-44B
(Page 1 of 1)
Date/Time Started : 06/10/11
Date/Time Completed : 06/10/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
15
20
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.3
4.0/2.8
4.0/3.7
4.0/3.5
2.4/3.1
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, pale brown (10YR 6/3), very fine- to medium-grained sand (~80%), well graded, subrounded, loose, dry, HCl moderate, fine crystals precipitate throughout
4.0-6.0' Clayey Sitly SAND, very pale brown (10YR 7/4), very fine-grained sand (~60%), poorly graded,
subrounded, loose, slightly plastic, dry, HCL none, small rocks, wood scattered throughout
6.0-8.0' Clayey Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~60%), poorly graded,
subrounded, slightly plastic, moist, HCl weak
8.0-12' Lean CLAY, dark reddish brown (5YR 3/2), silt, soft, slightly plastic, moist, HCl weak
12-14.3' Sandy Lean CLAY, dark reddish brown (5YR 3/2), very fine-grained sand (~20%), poorly graded, subrounded, very soft, plastic to very plastic, very cohesive, moist, HCl weak
14.3-16' Lean CLAY, gray to blueish gray (2 6/1), hard, plastic, non-cohesive, moist, HCl none, laminate
bedding, weathered shale
16-18' Lean CLAY, blueish gray to gray (2 6/1), loose, plastic, moist, HCl none, thin bedding, FeO staining throughout, weathered shale
18-18.4' SILT, blueish gray to gray (2 5/1), hard, laminate bedding, shale fragments
Total depth of boring 18.4' bgs (refusal)
US
C
S
SW/SM
SM/SC
CL
CL/CH
CL
ML
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
5
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Duplicate sample collected. Sample interval was increased to 2 feet to accommodate
for additional sample volume required by the analytical laboratory.
Log of Soil Boring GP-45B
(Page 1 of 1)
Date/Time Started : 06/07/11
Date/Time Completed : 06/07/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.0
0.6/0.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, dark reddish brown (5YR 3/4), fine- to very fine-grained sand, poorly graded, subangular to subrounded, very loose, moist to wet, HCl none, roots 0-2' bgs
4.0-4.6' SAND w/ minor silt, pinkish gray (5YR 6/2), very fine- to fine-grained sand, poorly graded,
subangular to subrounded, very loose, moist, HCl none
Total depth of boring 4.6' bgs (refusal)
US
C
S
SM
SP/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
6
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-46B
(Page 1 of 1)
Date/Time Started : 06/07/11
Date/Time Completed : 06/07/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.8
0.3/0.6
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-3.7' Silty SAND, dark reddish brown (5YR 3/4), very fine-grained sand (~70%), poorly graded, subangular to subrounded, very loose, moist to wet, HCl slight
3.7-4.3' SAND w/ minor silt, yellowish red (5YR 5/6), very fine- to fine-grained sand, poorly graded, subangular to subrounded, very loose, moist, HCl none
Total depth of boring 4.3' bgs (refusal)
US
C
S
SM
SP/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
7
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-47B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.6
0.7/0.7
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.7' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand (~80%), poorly graded, subangular to subrounded, very loose to loose, moist to wet, HCl none, roots 0-2.5' bgs
Total depth of boring 4.7' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
4
8
B
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
Log of Soil Boring GP-48B
(Page 1 of 1)
Date/Time Started : 06/08/11
Date/Time Completed : 06/08/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : E. Muller
Depth
in
Feet
0
1
2
3
4
5
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
2.3/
DESCRIPTION
Sample Interval Description
Soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-2.0' Silty SAND, yellowish red (5YR 5/6), very fine-grained sand (~70%), poorly graded, subangular to subrounded, very loose, dry, HCl none, roots 0-1.4' bgs
2.0-2.3' SAND w/ minor Silt, light gray (10YR 7/2), very fine- to fine-grained sand, poorly graded,
subangular to subrounded, very loose, dry, HCl strong
Total depth of boring 2.3' bgs (refusal)
US
C
S
SM
SP/SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
1
C
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Field test soil sample not submitted to laboratory due to no detectable results during test kit analysis.
Log of Soil Boring GP-01C
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
3.5/2.8
DESCRIPTION
Sample
Field test sample collected; not submitted to lab (1)
Field test sample submitted for laboratory analysis
Duplicate soil sample not submitted for laboratory analysis
0-3.1' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none, trace white mottled HCl strong
3.1-3.5' Sandstone, pink (5YR 7/3), very fine- to fine-grained sand, dense, dry, HCl medium to strong
Total depth of boring 3.5' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
2
C
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Field test soil sample not submitted to laboratory due to no detectable results during test kit analysis.
Log of Soil Boring GP-02C
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
2.7/2.7
DESCRIPTION
Sample Interval Description
Field test soil sample collected; not submitted to lab (1)
Field test soil sample submitted for laboratory analysis
Duplicate soil sample not submitted for laboratory analysis
0-2.3' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl strong
2.3-2.7' Sandstone, brownish yellow (10YR 6/6), very fine- to fine-grained sand, poorly graded, loose to dense, dry, subangular to subrounded, HCl none
Total depth of boring 2.7' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
3
C
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Field test soil sample not submitted to laboratory due to no detectable results during test kit analysis.
Log of Soil Boring GP-03C
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/2.8
2.6/2.7
DESCRIPTION
Sample Interval Description
Field test soil sample collected; not submitted to lab (1)
Field test soil sample submitted for laboratory analysis
Duplicate soil sample submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none
4.0-5.4' Silty SAND, pink (5YR 7/4), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, trace fine sand, HCl medium to strong, white mottling w/ HCl strong
5.4-6.6' Sandstone, light brown gray (10YR 6/2), very fine- to fine-grained sand, loose to dense, dry, HCl none to weak, subangular to subrounded
Total depth of boring 6.6' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
4
C
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Field test soil sample not submitted to laboratory due to no detectable results during test kit analysis.
Log of Soil Boring GP-04C
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.3
1.5/1.7
DESCRIPTION
Sample Interval Description
Field test soil sample collected; not submitted to lab (1)
Field test soil sample submitted for laboratory analysis
Duplicate soil sample not submitted for laboratory analysis
0-5.1' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none, trace white mottling w/ HCl strong, roots at top
Total depth of boring 5.1' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
5
C
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Field test soil sample not submitted to laboratory due to no detectable results during test kit analysis.
Log of Soil Boring GP-05C
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.6
DESCRIPTION
Sample Interval Description
Field test soil sample collected; not submitted to lab (1)
Field test soil sample submitted for laboratory analysis
Duplicate soil sample not submitted for laboratory analysis
0-4.0' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose, dry, HCl none, trace white mottling w/ HCl strong
Total depth of boring 4.0' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
r
o
j
e
c
t
s
\
B
o
r
e
L
o
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\
D
e
n
i
s
o
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\
G
P
-
0
6
C
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Field test soil sample not submitted to laboratory due to no detectable results during test kit analysis.
Log of Soil Boring GP-06C
(Page 1 of 1)
Date/Time Started : 05/19/11
Date/Time Completed : 05/19/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.4
1.6/1.7
DESCRIPTION
Sample Interval Description
Field test soil sample collected; not submitted to lab (1)
Field test soil sample submitted for laboratory analysis
Duplicate soil sample not submitted for laboratory analysis
0-4.4' Silty SAND, yellowish red (5YR 4/6), very fine-grained sand, silt, poorly graded, loose to medium dense, dry, HCl none to strong, some white mottling w/ HCl strong 3.2-4.4' bgs
4.4-4.9' Silty SAND, pink (5YR 7/4), very fine-grained sand, silt, poorly graded, loose to medium dense, HCl strong, trace fine sand
4.9-5.6' Rock fragments, white, HCl none, very fine grained
Total depth of boring 5.6' bgs (refusal)
US
C
S
SM
GR
A
P
H
I
C
07
-
2
8
-
2
0
1
1

S
:
\
P
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j
e
c
t
s
\
B
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L
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g
s
\
D
e
n
i
s
o
n
\
G
P
-
0
7
C
.
b
o
r
White Mesa Mill, Blanding, Utah
Denison Nitrate Investigation
Project Name:
Project #: DENMC.C002.000
Note(s):
1. Field test soil sample not submitted to laboratory due to no detectable results during test kit analysis.
Log of Soil Boring GP-07C
(Page 1 of 1)
Date/Time Started : 05/18/11
Date/Time Completed : 05/18/11
Drilling Method : Geoprobe
Sampling Method : Continuous Dual Tube
Drilling Co./Driller : Earth Worx
Driller : L. Trujillo
Depth to Water : NA
Logged by : J. Reed
Depth
in
Feet
0
5
10
Sa
m
p
l
e

I
n
t
e
r
v
a
l
Pe
n
.
/
R
e
c
.

(
f
e
e
t
)
4.0/3.2
2.1/2.1
DESCRIPTION
Sample Interval Description
Field test soil sample collected; not submitted to lab (1)
Field test soil sample submitted for laboratory analysis
Duplicate soil sample not submitted for laboratory analysis
0-1.5' Sandy Clayey SILT, reddish brown (5YR 4/4), very fine-grained sand, medium stiff, dry to moist, cohesive, HCl none
1.5-1.7' CLAY, dark red brown (5YR 3/4), stiff, moist, medium plastic
1.7-4.9' Sandy SILT/Silty SAND, reddish brown (5YR 4/4), very fine-grained sand, silt, medium stiff/medium dense, slightly moist to moist, trace clay (cohesive), trace fine sand, HCl none to weak, trace white mottling at 2.5' bgs, little more sand or more silt
4.9-6.1' Silty SAND/SAND, brownish yellow (10YR 6/4), very fine- to fine-grained sand, silt (varying
amounts), medium dense, slightly moist, trace medium sand, slightly cohesive, HCl none, little iron stained
Total depth of boring 6.1' bgs (refusal)
US
C
S
ML
CL
ML/SM
SM/SP
GR
A
P
H
I
C

APPENDIX D

HISTORIC WATER LEVEL MAPS
(SEEP AND SPRING ELEVATIONS NOT CONSIDERED IN CONTOURING)

D.1
D.2
D.3

APPENDIX E

TOPOGRAPHIC AND GEOLOGIC MAPS

!
!
!
!
!
!
!
CORRAL CANYON
5624
CORRAL SPRINGS
5383
COTTONWOOD
5234
ENTRANCE SPRING
5560
FROG POND
5590
RUIN SPRING
5380
WESTWATER
5468
Approved Date Author Date File Name Figure
HYDRO
GEO
CHEM, INC.
SEEPS AND SPRINGS
ON USGS TOPOGRAPHIC BASE
WHITE MESA
7180002G09/17/10SJS 707/16/10DRS
0.5 0 0.5 10.25
Mile
Cell No. 1
Cell No. 3
Cell No. 2
Cell No. 4A
NK:\718000\GIS\7180002G.mxd: Friday, September 17, 2010 1:02:59 PM
Cell No. 4B
WESTWATER
5468
Seep or Spring
Elevation (feet) above mean sea level
0.5 10
Mile
E
E
E
E
E
E
E
Cell No. 1
Cell No. 2
Cell No. 3
Cell No. 4A
Qh
Qlbb
Qlbb
Qlbb
Kdb
Kdb
Kdb
Kdb
Kdb
Kdb
Jmb
Jmb
Jmb
Jmb
Jmb
Jmb
Qea
Qea
Qea
Qea
Qa
Qa
Qa
Qa
Qa
Kdb
Kdb
Jmb
Qa
Cell No. 4B
Jmw
Jmr
Qh
Qea
Jmr
Jmw
Kdb
Jmb
Kdb
Kdb
CORRAL CANYON
CORRAL SPRINGS
COTTONWOOD
ENTRANCE SPRING
FROG POND
RUIN SPRING
WESTWATER
GEOLOGIC MAP
WHITE MESA, UTAH
SJSÒApproved Date File Figure
HYDRO
GEO
CHEM, INC.12/28/11
Geological Map of the Blanding Area, San Juan County, Utah (modified from Haynes et al., 1962; Dames & Moore, 1978 and Kirby, 2008)
Base Map Prepared from Portions of the Blanding South, Black Mesa Butte, Big Bench and No Mans Land U.S.G.S. 7.5' Quadrangles.
K:\718000\GIS\Geology E.2
Contact - dashed where uncertain
E Seep or Spring
EXPLANATION
Tailing Cell
Artificial cut and fill
Stream alluvium
Slumps and landslides, Brushy Basin
Mixed eolian and alluvial deposits
Dakota and Burro Canyon Formations (undivided)
Brushy Basin Member of the Morrison Formation
Westwater Canyon Member of the Morrison Formation
Recapture Member of the Morrison Formation
QhQhQhQh
QaQaQaQa
QlbbQlbbQlbbQlbb
QeaQeaQeaQea
KdbKdbKdbKdb
JmbJmbJmbJmb
JmwJmwJmwJmw
JmrJmrJmrJmr

APPENDIX F

HYDROGEOLOGY BENEATH PROPOSED CELLS 5A AND 5B AND
PROPOSED NEW MONITORING INSTALLATIONS

F.1
Appendix F: H:\718000\Hydrpt2022\Report\Appf\Cellsa5b_Final.Docx

HYDROGEOLOGY OF THE AREA NEAR PROPOSED CELLS 5A AND
5B AND RECOMMENDED LOCATIONS OF NEW PERCHED
MONITORING WELLS
The hydrogeology of the portion of the site beneath proposed cells 5A and 5B, the recommended
placement of new perched groundwater monitoring wells, and the rationale for the recommended
placement and spacing of wells is discussed in the following Sections.
Hydrogeology
Figure F.1 is a fourth quarter, 2022 perched groundwater level contour map showing the
locations of hydrogeologic cross-sections in the vicinity of proposed new cells 5A and 5B. Cross
section WNW-ESE (Figure F.2) extends from piezometer DR-7 (to the west of proposed cell
5A), along the upgradient (northern) dikes of proposed cells 5A and 5B, to MW-17, located on
the east dike of proposed cell 5B. Cross section W2-E2 (Figure F.3) extends from piezometer
DR-8 (to the west of proposed cell 5A), beneath the southwest corner of proposed cell 5A, to
MW-17 on the east dike of proposed cell 5B.
The hydrogeology depicted on cross-sections in Figures F.2 and F.3 is similar to the
hydrogeology beneath the existing tailings management system (TMS) at the site. Alluvium is
underlain locally by Mancos Shale. The alluvium (and Mancos where present) is (are) underlain
by Dakota Sandstone and Burro Canyon Formation. Both are sandstones that are often not
readily distinguishable in the field and are not separately defined on the cross sections. The
Burro Canyon Formation is underlain by the Brushy Basin Member of the Morrison Formation.
The Brushy Basin Member, a bentonitic shale, functions as an aquiclude supporting the perched
groundwater system.
The Dakota Sandstone and Burro Canyon Formations locally contain relatively thin, sub-
horizontal, interbedded shale and conglomerate horizons that are often discontinuous between
boreholes. Although the lithology shown for MW-17 is more general (due to the less-detailed
nature of the log for the boring), shale and ‘conglomeratic’ horizons within the Burro Canyon
and Dakota are described in the log (Appendix A [main report]). Detailed logs showing
variations in the lithology of the Dakota and Burro Canyon for MW-14 and MW-15 are
unavailable.
Figures F.2 and F.3 show that perched groundwater saturated thicknesses vary from negligible at
MW-33 (a consistently dry well located at the northwest corner of proposed cell 5A) to
approximately 33 feet at MW-17 (located on the east dike of proposed cell 5B). Figure F.1 shows
that a dry area extends from beneath cell 4B under the northwest portion of proposed cell 5A.
F.2
Appendix F: H:\718000\Hydrpt2022\Report\Appf\Cellsa5b_Final.Docx

Figure F.1 also shows that perched groundwater flow beneath the proposed cells is generally to
the south-southwest, towards perched groundwater discharge point Ruin Spring.
As discussed in Section 3.1.2 of the main text, porosity within the Dakota Sandstone and Burro
Canyon Formation is primarily intergranular, and no significant joints or fractures have been
documented in any wells or borings installed across the site (Knight-Piésold, 1998). Any
fractures observed in cores collected from site borings are typically cemented, showing no open
space. The Knight-Piésold findings are consistent with the evaluation of a 1994 drilling program
provided in HGC (2001a) and with examination of drill core samples collected during
installation of MW-3A, MW-23, MW-24, MW-28, MW-30, and TW4-22 in 2005 (HGC, 2005).
The installation of proposed cells 5A and 5B will extend the TMS farther downgradient; the
southern (downgradient) boundary will be closer to perched water discharge point Ruin Spring.
However, as noted in Section 2.1.3 of the main text, hydraulic conductivities and perched water
migration rates to the southwest of the TMS (between the TMS and Ruin Spring) are among the
lowest at the site.
Figure F.4 depicts inferred perched groundwater flow pathlines downgradient of the existing
TMS, and beneath and downgradient of proposed cells 5A and 5B. Figure F.5 depicts the
shortest pathline from the downgradient (southern) dikes of proposed cells 5A and 5B to the
nearest discharge point, Ruin Spring. The length of this pathline is approximately 8,550 feet.
Using an average hydraulic conductivity of 14.1 ft/yr (as calculated for Path 6 in Figure 27 of the
main text), the Figure F.5 path length of 8,550 feet, an average hydraulic gradient of 0.0125 ft/ft
(between DR-13 and Ruin Spring), and a porosity of 0.18, the estimated average groundwater
pore velocity is approximately 0.98 ft/yr. The estimated time for perched groundwater to travel
from the downgradient edge of proposed cells 5A and 5B to Ruin Spring is therefore
approximately 8,720 years.
Recommended Well Locations
Seven new perched groundwater monitoring wells (MW-42 through MW-48; and one new
piezometer, DR-26; as shown in Figure F.6) are proposed to monitor proposed cells 5A and 5B.
Cell 5A and associated groundwater monitoring wells are to be installed first. Therefore,
proposed groundwater monitoring wells MW-42 through MW-45; and piezometer DR-26; would
be installed as part of the construction of cell 5A. MW-46 through MW-48 would be installed
later as part of the construction of cell 5B. Proposed wells MW-42 through MW-45; and
piezometer DR-26; are considered adequate to monitor proposed cell 5A even if the construction
of cell 5B is delayed indefinitely.
F.3
Appendix F: H:\718000\Hydrpt2022\Report\Appf\Cellsa5b_Final.Docx

As discussed in HGC (2018) these proposed wells will be located far down- to cross-gradient of
the nitrate plume (shown on Figure F.6 and discussed in the main text) and will provide
additional information regarding groundwater conditions (saturated thicknesses and flow
directions) in the downgradient area.
MW-42 through MW-48 will provide an additional ‘line of defense’ of wells to augment the two
east-west lines of wells that are currently located down- to cross-gradient of the nitrate plume.
The current lines of wells include:
MW-5, MW-11, MW12, MW-23 and MW-25, along the downgradient margin of cell 3;
and
MW-14, MW-15, MW-34, MW-35, MW-36 and MW-37, along the downgradient
margin(s) of cells 4A and 4B

In addition, existing wells MW-17 and MW-38 are located cross-gradient and far cross-gradient
of the nitrate plume; and MW-3A and MW-20 are located far downgradient of the nitrate plume.
Due to the location of proposed cell 5A above and near the structural high in the Brushy Basin
Member surface, three of the proposed wells (MW-42, MW-43 and MW-44) are (unavoidably)
expected to have relatively small saturated thicknesses, although MW-43 and MW-44 are likely
to have saturated thicknesses of at least 5 feet or greater. As its proposed position is likely near
the crest of the structural high, piezometer DR-26 is expected to be dry.
Narrow-diameter pilot borings are proposed to be installed to ensure adequate saturated
thicknesses within the proposed monitoring wells (with the exception of piezometer DR-26).
Should the saturated thickness within a pilot boring be inadequate (less than 5 feet), the boring
(with the concurrence of DWMRC) will either be converted to a piezometer or abandoned. A
new pilot boring will be installed within approximately 100 feet in a direction along the cell
margin likely to have adequate saturated thickness. Pilot borings having saturated thicknesses of
5 feet or greater will be reamed and completed as monitoring wells.
The spacing of the five wells (MW-43 through MW-47) along the southern (downgradient) dikes
of the proposed cells is similar to the spacing of existing wells along the southern (downgradient)
dikes of cells 4A and 4B. Proposed well MW-42 and piezometer DR-26 along the west dike of
proposed cell 5A are generally cross-gradient with respect to groundwater flow; and existing
well MW-17 and proposed well MW-48 along the east dike of proposed cell 5B are generally up-
to cross-gradient with respect to groundwater flow.
F.4
Appendix F: H:\718000\Hydrpt2022\Report\Appf\Cellsa5b_Final.Docx

The spacing of the proposed wells (approximately 750 ft or closer) is conservative with regard to
reliable detection of potential future impacts to groundwater that may arise from any future
seepage from the proposed cells. As discussed in HGC (2001b), numerical simulations of
hypothetical ‘point’ source ‘leaks’ from the existing TMS indicate that such leaks could be
reliably detected using well spacings of between 850 and 900 ft. However, the advanced design
and leak detection systems that are to be incorporated in the construction of the proposed cells
makes it highly unlikely that any potential future seepage could bypass the leak detection
systems to an extent that could impact groundwater. The proposed well spacing is likely overly
conservative considering that the cell design includes multiple liners with a leak detection system
installed between the liners.
Simulations of hypothetical ‘leaks’ presented in HGC (2001b) assumed a relatively conservative
10:1 ratio of horizontal to vertical permeability within vadose materials (unsaturated Dakota
Sandstone and Burro Canyon Formation) underlying the TMS at the site. In reality, the effective
ratio of horizontal to vertical permeability is likely to be larger than 10:1, making the resulting
potential for lateral spreading, and the reliability of the monitoring well network, greater than
was simulated. A large ratio of horizontal to vertical permeability is likely to exist due to the sub-
horizontal layering that is present in both the Dakota Sandstone and Burro Canyon Formation.
The conclusions based on the HGC (2001b) simulations were confirmed by more recent
numerical modeling of the adequacy of well spacing provided in HGC (2019). These simulations
assumed ‘worst-case’ conditions and were based on conservative assumptions that included the
same 10:1 ratio of horizontal to vertical permeability. Simulations assumed hypothetical ‘point’
source ‘leaks’ of 0.1 and 1 gallons per minute (gpm) at locations halfway between proposed
wells MW-45 and MW-46; and halfway between proposed wells MW-46 and MW-47. Any such
‘leaks’ would be the most difficult to detect because they would occur at the downgradient edge
of the proposed cells at the maximum distance from the two nearest wells. Because of the nearest
wells’ position along the downgradient edge of the TMS, these wells would be mainly cross-
gradient of the hypothetical ‘leak’.
In all simulated cases, assuming worst-case conditions, potential impacts are predicted to spread
sufficiently cross-gradient to allow timely detection using the proposed well spacing. The
proposed well spacing was concluded to be more than adequate to detect both changes in
concentration and saturated thicknesses resulting from these hypothetical ‘leaks’. Specifically,
simulation results indicated that impacts to groundwater would be detected by wells proposed
along the southern margins of cells 5A and 5B more than 100 years before they would be
detected at the next closest downgradient well MW-3A. Under conditions assuming a
F.5
Appendix F: H:\718000\Hydrpt2022\Report\Appf\Cellsa5b_Final.Docx

hypothetical 1 gpm ‘leak’, impacts would be detected along the cell margin in less than 50 years;
and under conditions assuming a hypothetical 0.1 gpm ‘leak’, within 100 to 200 years.
In addition, interbedded sub-horizontal shale and/or coarse-grained (conglomeratic) horizons that
exist beneath proposed cells 5A and 5B (Figures F.2 and F.3) are both likely to enhance lateral
spreading of any future seepage that may potentially originate from the proposed cells. Such
lateral spreading would increase the area of perched groundwater impacted by any potential
future seepage and thus reduce the number of wells needed for reliable detection.
Sub-horizontal shale horizons are expected to have low vertical permeability (and therefore low
vertical hydraulic conductivity). Any seepage percolating vertically downward that encountered
a shale horizon would be likely to perch, then spread laterally. Lateral spreading would continue
until the perched area was large enough that seepage through the low-permeability shale became
equal to the incoming seepage rate. The footprint of seepage through the base of the shale
horizon would thus be larger than the footprint of incoming seepage above the shale horizon.
Sub-horizontal coarse-grained (conglomeratic) horizons at the site may have either relatively
high or relatively low permeability depending on the degree of cementation. HGC (2010a and
2010b) summarize the lithology and hydraulic testing of angle borings GH-94-1 and GH-94-2A
(angled beneath cell 3, as described in HGC, 2001a). The majority of the hydraulic tests within
these angle borings were conducted within the vadose zone and are considered generally
representative of vadose conditions beneath the TMS. The test results discussed in HGC (2010a
and 2010b) indicate the following:
Horizontal hydraulic conductivities of the Dakota Sandstone ranged from 5.9 x 10-6
centimeters per second (cm/s) to 8.8 x 10-5 cm/s; horizontal hydraulic conductivities of the
underlying Burro Canyon Formation ranged from 4 x 10-5 cm/s to 6.3 x 10-4 cm/s. Less
than half of the higher conductivities occurred in conglomeratic materials, with three of
the tests conducted in conglomeratic material yielding conductivity estimates less than 10-
5 cm/s. Only one test yielded a conductivity estimate greater than 10-5 cm/s.
The available (pre-2010) borehole data near cell 4B indicate poor correlation between
conglomeratic intervals and enhanced permeability. Only one (possibly two) reported
zone(s) of higher permeability within conglomeratic materials exist(s) near the saturated
portion of the Burro Canyon Formation. Cross-gradient to up-gradient (east to northeast)
of the TMS, in the vicinity of the chloroform plume, conglomeratic materials within the
deep saturated Burro Canyon Formation appear to be associated with higher permeability,
at least in the vicinity of MW-4 (within the chloroform plume). However, available data
from the vicinity of cell 4B do not indicate a consistent association between conglomeratic
materials and higher permeability in the vadose zone.
Overall, vadose conglomeratic intervals do not consistently have higher hydraulic
conductivities (or permeabilities) than the surrounding sandstones. However,
F.6
Appendix F: H:\718000\Hydrpt2022\Report\Appf\Cellsa5b_Final.Docx

conglomeratic intervals having higher conductivities than surrounding materials would
likely spread any seepage laterally so that the seepage would contact a larger area of
perched groundwater.

With regard to lateral spreading, potential seepage encountering a relatively high permeability,
sub-horizontal conglomeratic horizon is expected to spread laterally as a result of two factors: 1)
the conglomeratic material would likely behave as a capillary barrier; and 2) the relatively high
lateral permeability of the conglomeratic material would facilitate lateral spreading of any
seepage percolating into the material.
First, as a capillary barrier, a relatively high permeability conglomeratic material would prevent
infiltration of seepage from finer-grained, lower-permeability, overlying materials until near-
saturated conditions were reached in the overlying material above the contact. As saturations
build up within the overlying materials, the potential for lateral spreading increases.
Second, any seepage percolating into a relatively high permeability conglomeratic horizon would
tend to perch on the underlying lower permeability materials, causing lateral spreading within the
conglomeratic horizon, and increasing the area of the underlying materials impacted by the
continuing downward percolation of the seepage.
Overall, the vertical heterogeneity encountered beneath proposed cells 5A and 5B is expected to
enhance the likelihood for timely detection of any groundwater impacts from any potential future
seepage originating from the cells. Furthermore, as discussed above, improvements in cell design
since installation of cells 1 through 3 at the site make it highly unlikely that any potential future
seepage could bypass the leak detection systems incorporated in proposed cells 5A and 5B to an
extent that could impact groundwater.

F.7
Appendix F: H:\718000\Hydrpt2022\Report\Appf\Cellsa5b_Final.Docx

References
HGC. 2001a. Letter to Mr. Harold Roberts, International Uranium Corporation (Regarding the
Review of the 1994 Drilling Program). June 21, 2001.
HGC. 2001b. Assessment of the Effectiveness of Using Existing Monitoring Wells for GWDP
Detection Monitoring at the White Mesa Uranium Mill, Blanding, Utah. September 25,
2001.
HGC. 2005. Perched Monitoring Well Installation and Testing at the White Mesa Uranium Mill,
April through June 2005. August 3, 2005.
HGC, 2018. Revised Phase III Nitrate Corrective Action Planning Document and Recommended
Phase III Corrective Action. White Mesa Uranium Mill Near Blanding, Utah. December
13, 2018.
HGC, 2019. Letter to Ms. Kathy Weinel Re: Numerical Transport Simulations to Support
Proposed Cell 5A and 5B Well Spacing. March 7, 2019.
Knight-Piésold. 1998. Evaluation of Potential for Tailings Cell Discharge – White Mesa Mill.
Attachment 5, Groundwater Information Report, White Mesa Uranium Mill, Blanding,
Utah. Submitted to UDEQ.

APPENDIX F

FIGURES
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
H:/718000/hyrpt2022/
report/AppF/Uwl1221c5a5b.srf
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
saturated thickness estimated
to be less than 5 feet
5500
4th quarter 2021 water level
contour and label in feet amsl
SJS
PROPOSED CELLS 5A AND 5B
(showing kriged Q4 2021 perched water levels
and cross sections in proposed cell area)
WHITE MESA SITE
F.1
APPROVED DATE REFERENCE FIGURE
HYDRO
GEO
CHEM, INC.
EXPLANATION
Qal/Fill
Km
Kdbc
Jmbb
Mancos Shale
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member
of Morrison Formation
Piezometric surface
vertical exaggeration = 5:1
Shale/Shaly Sandstone within
Dakota/Burro Canyon
Conglomerate within
Dakota/Burro Canyon
INTERPRETIVE EAST-WEST
CROSS SECTION (WNW - ESE)
SOUTHWEST INVESTIGATION AREA
H:/718000/hydrpt2022/
report/AppF/wnwesexssw.srf
* = detailed log unavailable
Conglomeratic Dakota Sandstone/
Burro Canyon Formation
SJS
5450
5475
5500
5525
5550
5575
5600
5625
5650
5675
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
DR
-
7
MW
-
3
6
MW
-
3
3
MW
-
3
4
MW
-
3
7
MW
-
1
5
*
MW
-
1
4
*
MW
-
1
7
Qal/Fill Qal/FillKm
Kdbc
Kdbc
Jmbb
WNW ESE
proposed cell 5A proposed cell 5B
F.2
Alluvium/Fill/
Weathered Mancos
APPROVED DATE REFERENCE FIGURE
HYDRO
GEO
CHEM, INC.
EXPLANATION
Qal/Fill
Km
Kdbc
Jmbb
Alluvium/Fill
Mancos Shale
Dakota Sandstone/
Burro Canyon Formation
Brushy Basin Member
of Morrison Formation
Piezometric surface
vertical exaggeration = 15:1
Shale/Shaly Sandstone within
Dakota/Burro Canyon
Conglomerate within
Dakota/Burro Canyon
INTERPRETIVE EAST-WEST
CROSS SECTION (W2 - E2)
PROPOSED CELL 5A/5B AREA
Conglomeratic Dakota Sandstone/
Burro Canyon Formation
SJS
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500
distance (feet)
5450
5475
5500
5525
5550
5575
5600
5625
el
e
v
a
t
i
o
n

(
f
e
e
t

a
m
s
l
)
DR
-
8
DR
-
9
DR
-
1
0
DR
-
1
1
DR
-
1
2
DR
-
1
3
MW
-
1
7
Qal
Km Km
Kdbc Kdbc
Jmbb
Jmbb
W2 E2
proposed Cell 5A proposed Cell 5B
F.3 H:/718000/hydrpt2022/
report/AppF/e2w2xssw.srf
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
F.4
estimated area having saturated
thickness less than 5 feet
estimated perched water flow path
SJS H:/718000/hydrpt2022/
report/AppF/Uwl1221c5a5b_path.srf
PROPOSED LOCATIONS OF CELLS 5A AND 5B
(showing kriged Q4 2021 perched water levels and inferred
perched water flow paths downgradient of the tailings
management system)
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well showing
elevation in feet amsl
perched piezometer showing
elevation in feet amsl
seep or spring showing
elevation in feet amsl
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
showing elevation in feet amsl
temporary perched nitrate monitoring
well showing elevation in feet amsl
TW4-12
TWN-7
5504
5569
5569
5588
5380
5463
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021showing
elevation in feet amsl
5524
temporary perched monitoring
well installed September, 2021
showing elevation in feet amsl
TW4-43
TWN-20
F.5
estimated area having saturated
thickness less than 5 feet
SJS H:/718000/hydrpt2022/
report/AppF/Uwl1221c5a5b_path6B.srf
PROPOSED LOCATIONS OF CELLS 5A AND 5B
(showing kriged Q4 2021 perched water levels and inferred
perched water flow paths downgradient of the tailings
management system)
estimated shortest perched water flow
path to nearest discharge point
HYDRO
GEO
CHEM, INC.
EXPLANATION
perched monitoring well
perched piezometer
seep or spring
MW-5
PIEZ-1
RUIN SPRING
temporary perched monitoring well
temporary perched nitrate monitoring
well
TW4-12
TWN-7
MW-38
TW4-42
temporary perched nitrate monitoring
well installed April, 2021
temporary perched monitoring
well installed September, 2021
TW4-43
TWN-20
saturated thickness estimated
to be less than 5 feet
5500
4th quarter 2021 water level
contour and label in feet amsl
PROPOSED NEW CELL 5A AND 5B
MONITORING WELLS AND PIEZOMETER
WHITE MESA SITE
H:/718000/hydrpt2022/
report/AppF/UwlPropWellC5_r1.srf F.6SJS
MW-42
DR-26