DRC-2011-008636 - 0901a06880afdc0b

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WORK FLAN AND SCHENUTH FOR
SU PPLEM ENTAT CONTAIIil I NANT
INVE$TIGATION REPORT FQR UIfHITE ifrESA
MILL NITRATE INVESTIGATION
Blanding, Utah
Prepared for:
DENrsoo//
fi,llNEs
Denison Mines (USA) Corp.
1050 lTth Street, Suite 950
Denver, Colorado 80265
Prepared by:remtEt&
6000 Uptown Boulevard NE, Suite 220
Albuquerque, New Mexico 87110
February 14,2011
4.0
5.0
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1.1 Historical Land Use and Geomorphologic Study ............... 31.2 Investigation of Potential Natural Nitrate Reservoir .......... 31.3 Investigation of Potential Nitrate Source Locations ...........41.4 Stable Isotope Study .......................41.5 Mass Balance Calculations .......... ..................... 6
GEOLOGY AND HYDROGEOLOGY ....................7
PROJECT MANAGEMENT.....,..8
3.1 Field Documentation. ...................... 83.2 Health and Safety .......... 8
HISTORICAL LAND USE AND GEOMORPHOLOGIC STUDY.... ......9
4.1 Initial Procedure. ...........94.2 Initial Conclusions and Recommendations.............. ......... l0
INVESTIGATION OF NATURALLY OCCURRING NITRATE RESERVOIR INso[........ .............12
5.1 Geoprobe Nitrate and Chloride Investigation......... .......... 135.2 Coring Study to Explore for Mtural Nitrate Reservoir.. .................... l5
INVESTIGATION OF POTENTIAL NITRATE SOURCE LOCATIONS............. 17
6.1 Geoprobe Investigation of Potential Nitrate Source Locations ..........176.2 Coring Study in Potential Nitrate Source Locations.. ....... 19
STABLE ISOTOPES STUDY ...............20
MASS BALANCE CALCULATIONS ,....24
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Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure l4
Figure 15
Figure 16
Figure l7
Figure 18
Figure 19
Figure 20
Figure 2l
Pigne 22
LIST OF FIGURES
Flow Chart Depicting the Logical Progression of Additional Studies
6lsN results from Sampling of Various Sources of Nitrate Contamination
6lsN Results Normalized to N2 in the Atmosphere from Sampling a Wider Range
of Sources
A Plot of 6180 versus 6l5N
Location Map
Historical Aerial Imagery, 1937 Aerial Photo
Historical Aerial Imagery, 1955 Aerial Photo
Historical Aerial Imagery, June 30, 1985 Landsat
Historical Aerial Imagery, 1997 DOQQ
Historical Aerial Imagery, 2006 DOQQ
Historical Aerial Imagery, 2009 DOQQ
Pasture Coincident with Drainages
Outline of 1955 Pasture Overlain over the USGS Topographic Map
2006 Aerial Photograph Showing the Stock Pond
Pasture Areas Interpreted from 1955 Imagery
Location of Black Mesa Relative to White Mesa
Radar Site at White Mesa near Blanding, Utah, J:urire 2I,1967
Bivouac Site at White Mesa near Blanding, Utah, June 21,1967
Site Map with DUSA Property Boundary
Natural Nitrate Reservoir: Geoprobe Boring Locations
Nitrate Source Areas: Geoprobe Boring and Core Drilling Locations
Stable Isotope Sampling Wells
LIST OF TABLES
Project Schedule
Laboratory Analytical Parameters by Task and Media
Table 1
Table2
LIST OF APPENDICES
Appendix A Nitrate Extraction and Field Test Procedure
Appendix B Analytical Methods List
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bgs
CCD
CFC
CIR
cm/sed
6
DEQ
DRC
DUSA
fl/yr
GPS
HASP
i
IAEA
k
m
n
NIST
Site
SMOW
SPLP
USCS
USGS
ACRONYMS AND ABBREVIATIONS
below ground surface
counter current decant circuit
chlorofluorocarbons
Contaminant Investigation Report
centimeters per second
delta
Department of Environmental Quality
Utah Division of Radiation Control
Denison USA
feet per year
global positioning system
health and safety plan
average gradient
Intemational Atomic Energy Agency
hydraulic conductivity
meter
porosity
National Institute of Standards and Technology
White Mesa Mill property
Standard Mean Ocean Water
synthetic precipitation leaching procedure
Unified Soil Classification System
United States Geological Survey
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1.0 INTRODUCTION
Denison Mines (USA) Corp. (DUSA) and the Co-Executive Secretary of the Utah Water auanty
Board (Co.Executive Secretary) entered into a Stipulated Consent Agreement Docket No.
UGW09-03 dated January 27, 2009 (Consent Agreement) related to nitrate contamination at
DUSA's White Mesa Uranium Mill Site, Blanding Utah (Mill). Pursuant to Item 6.,4' of the
Consent Agreement, DUSA submitted a Nitrate Contamination lnvestigation Report, White
Mesa Uranium Mill Site, Blanding Utah, dated December 30,2009 (CIR) to the Utah Division of
Radiation Control (DRC). By a letter dated October 5, 2010 and hand delivered to DUSA on the
same date, the Co-Executive Secretary notified DUSA of his determination that the CIR is
incomplete (October 5, 2010 DRC Notice). As a result of this determination under Item 7.C of
the Consent Agreement, DUSA is to remedy such omissions in the CIR on or before November
4,2010.
By an email transmitted to the Co-Executive Secretary on October 20, 2010, and pursuant to
Item 11 of the Consent Agreement, DUSA requested an amendment to the deadline stipulated in
item 7.C of the Consent Agreement, which required that Denison must remedy any omissions in,
content requirements of or failure to meet any performance standards or objectives relating to
the CIR mandated by Item 6.,4. of the Consent Agreement, within 30 calendar days of receipt of
the October 5, 2010 DRC Notice (i.e., November 4,2010).Instead, DUSA requested item 7.C be
amended as follows: a. DUSA representatives would meet with the Co-Executive Secretary and
his legal counsel within two weeks from the date of the email to discuss the legal responsibilities
of DUSA with respect to the nitrate contamination; b. Once the legal responsibilities of DUSA
with respect to the nitrate contamination have been determined, DUSA would, within 30 days
after such a determination was made, submit to the Co-Executive Secretary for approval a plan
and schedule to perform any further investigations that may be required in order to remedy any
such omissions, content requirements or failures of performance standards, and to submit a
revised CIR; and c. DUSA would perform such investigations and submit a revised CIR in
accordance with the agreed upon plan and schedule.
On October 26, 2010, DUSA met with the Co-Executive Secretary, DRC staff and legal counsel
(October 26, 2010 Meeting) to discuss DUSA's legal obligations with respect to the nitrate
contamination. At the meeting, DUSA reported that it was premature to submit a schedule for
submittal of performance standards and a Corrective Action Plan for the nitrate contamination. [n
tum, DUSA presented a new theory for a possible source of the nitrate and chloride
contamination beneath the Mill, based on DUSA's review of the scientific literature (New
Theory). Based on this New Theory, DUSA suggested that the nitrate contamination source is or
could be caused by naturally occurring nitrate and chloride salt deposits located in the vadose
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zone near or beneath the Mill site area, which have been mobilized by natural and/or artificial
recharge. The parties agreed that this New Theory warranted additional investigation, along with
certain of the other additional studies suggested in the October 5, 2010 DRC Notice. As agreed at
the October 26,2010 meeting, DUSA submitted via email on November 15, 2010, a letter setting
out the additional studies to be considered that have been identified to date, including the
additional studies suggested in the October 5, 2010 DRC Notice, proposed additional studies
relating to the New Theory, and any other additional studies that DUSA believes may bc
relevant. tn the November 15, 2010 letter, DUSA proposed that a meeting be held on November
30, 2010 betrreen DRC Staffand DUSA technical and regulatory staffto discuss the foregoing
studies and any associated matte6, to agree on the studies to be performed and the manner of
perfomring those studies, and to develop a plan and schcdule for performing such studies and for
zubmittal of a revised CIR
The meeting contemplated in DUSA's November 15, 2010 letter was held on November 3Q
2010, among DRC Staff and DUSA technical and regulatory staff. At that meeting, DUSA
presented a number of additional studies (herein "Additional Sfirdies) to be perfomred by
DUSA in order to complete the CIR. The Additional Studies were in addition to the New Theory.
The Co-Executive Secretary and DUSA further agreed that DUSA would pr€,pare a detailed plan
and schedule (the "Plan and Schedule") for performing zuch studies and for submittal of a
revised CIR that meets the requirements of all applicable regulations on or before February 15,
2011. The February 15, 201I date for submittal of the Plan and Schedule is somewhat ldsr rhan
the original 30 days proposed by DUSA in its October 20,2OlO €mail to the Co-Executive
Secretar5r, due to the complexity of certain of the Additional Studies to be pcrformed- During the
November 30, 2010 meeting it was a.geed Orat both the Plan and Schedule and the revised CrR
will be subject to Co.Executive Sccretary approval. DUSA's commitment to preparc and submit
the Plan and Schedule is set out in a Tolling Agreement (the 'Tolling Agreement') dated
December 15, 2010 between DUSA and the Co-Executive Secrctary.
This document is the Plan and Schedule, which is being submitted in accordance with the Tolling
Agreement. The purpose of this Plan and Schedule is to define the Additional Studies and to
propose a plan and schedule to complete those studies and submit a revised CIR. DUSA
proposes the Additional Studies described below. A flow chart depicting the logical progression
of additional studies is presented as Figure 1 and a schedule chart showing the expected duration
of each task and subtask is presented as Tablel and is organized by number of months after this
document is approved. The plan and schedule presented here should be considered to be for
Phase 1 of the investigation. Phase 2 would be initiated if Phase 1 encounters items or new
information that requires additional study, such as any additional studies that may be needed to
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gain statistical power or to investigate any new findings. The schedule set out in Table 1
assumes that field work will commence in April 2011 and end in October 2011. This may allow
for some iterations and additional field work if warranted from a review of initial results.
Laboratory results for some of the isotopic analysis may take up to three months to receive, after
the end of the field season. The final mass balance analysis will not commence until all
laboratory data has been obtained. The final report will be prepared after the final mass balance
analysis has been completed.
1.1 Historical Land Use and Geomorphologic Study
A further evaluation of historical land use in the vicinity of the White Mesa Mill property (site)
will be performed in order to supplement the source evaluation (the "Source Review Report")
that was included in the CIR. This further evaluation is currently under way and will (a) identify
areas that have been subject to agricultural activities and (b) evaluate land-use practices that may
have led to elevated levels of nitrate and other contaminants in groundwater. Objective (a) is
also required to identify areas for sampling of buildup of atmospheric nitrogen, since we seek to
sample areas that have not been subject to anthropomorphic activities. This analysis includes
evaluation of historical aerial photography, historical Landsat satellite imagery, and an Internet-
based search of historic military activities in the region. This study is expected to take up to four
months to complete (Table l), due to the time required to research and obtain imagery. It is
described in more detail in Section 4.0 of this document.
1.2 lnvestigation of Poteitial Natural Nitrato Reservcrir
Using the results of the historical land use study, undisturbed alluvial soils on DUSA property at
locations that are close to site operations will be explored with a geoprobe for any potential
natural subsurface reservoir of nitrogen and chloride, as has been described by Wolvaard et al.,
2003) and to provide a background/baseline to the geoprobe study of potential sources identified
in the Source Review Report. The geoprobe portion of this study would start approximately one
month after this document is approved, and is expected to take approximately four months before
laboratory analysis is complete (Table 1). The coring portion of this study will follow the
geoprobing, starting approximately three months after approval of this document and taking four
months until laboratory analysis is complete. The study is described in more detail in Section 5.0
of this document.
If alluvial soils do not yield positive results for nitrate and chloride, coring of the bedrock units
would be performed in order to test the possibility that a reservoir of nitrate and chloride exists at
some level in the bedrock geologic column above groundwater, due to lack of distributed
recharge to groundwater over an extended period of time. [f so, keeping a hydraulic head on the
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wildlife pond may have mobilized constituents within this reservoir. Note that irrigation of fields
north of the site or any action that caused new infiltration to groundwater could have had the
same effect. It would be necessary to take core from an area that has not been affected by
focused recharge such as the wildlife ponds or intermittent streams and drainage channels.
Samples of core would be taken at regular intervals, moisfure content measured, and leached
with specific amounts of double distilled water to determine the concentrations of nitrate and
chloride present in soil moisture. Mass balance calculations could then integrate the mass of
nitrate and chloride in soil moisture to determine if the total mass is sufficient to account for the
observed concentrations in groundwater. The mass balance may or may not show that the nitrate
in the spiked horizon is enough to account for the nitrate plume.
1.3 lnvestigation of Potential Nitrate Source Locatons
Geoprobe samples will be collected from alluvial soils in or around specific potential sources
identified in the Source Review Report andanalyzed by SPLP for nitrate and chloride. This work
will only be useful in the unconsolidated soils at the site and would not be able to address the
bedrock units. If results of the geoprobe work indicate the presence of elevated nitrate or
chloride in alluvial soils a drill hole will be advanced through the alluvial material and a rock
core of the geologic formation beneath the alluvium will be drilled, in any of the 15 potential
nitrate source locations that are shown to contain elevated nitrate or chloride in the soil column
within the geoprobe soil samples and that are not active leach fields as identified by DUSA. The
geoprobe portion of this study would' start approximately one month after this document is
approved, and is expected to take approximately four months before laboratory analysis is
complete (Table 1). The coring portion of this study will follow the geoprobing, starting
approximately three months after approval of this document and taking four months until
laboratory analysis is complete. This study is described in more detail in Section 6.0 of this
document.
1.4 Stable lsotope Study
The stable isotope study is described in detail in Section 7.0 of this document, which contains
specifics on analytes to be sampled and sampling locations. The groundwater sampling portion
of this study would start approximately one month after this document is approved study and is
expected to take approximately seven months before laboratory analysis is complete (Table 1)
due to the non-standard laboratories that are required.
Stable (non-radioactive) isotopes of the same element differ by the number of neutrons in the
atomic nucleus. A variety of physical and biological processes can affect the relative
concentrations of light and heavy isotopes of the same element. This relative enrichment or
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depletion of one stable isotope over another is called isotopic fractionation. During evaporation,
for example, the heavier '8O becomes enriched in the residual water as more of the lighter 160
enters the vapor phase. Thus, meteoric water, derived largely from the evaporation of ocean
water, is enriched with 160 relative to ocean water.
For another example, nitrate in groundwater that has been denitrified by microbes, or originates
from human or animal waste is enriched with 15N. Measuring the relative proportions of stable
isotopes in water or other media can lead to interpretation of the source or sources for those
isotopes. Figure 2 shows 6l5N results from sampling of various sources of nitrate contamination,
including a uranium mill, from McQuillan et al (1989), showing the potential to exclude mill
tailings as a source of nitrate in groundwater, depending on the 61sN signature in the
groundwater. However, Figure 3 shows 6lsN results normalized to N2 in the atmosphere from
sampling a different set of sources indicating the complexity that could potentially be
encountered, raising the possibility that, while some sources can be readily distinguishable,
results of any isotopic study could be inconclusive for distinguishing other sources. Finally,
Figure 4 is a plot of 6180 versus 6r5N from Roadcap et al (2001), also showing the overlapping
nature of various sources but displaying the additional power of adding 618O.
A Tritium study to sample groundwater with high nitrate concentrations to confirm whether
groundwater with high nitrate is older or younger than the Mill was considered but rejected as a
duplication of previously collected information. Hurst and Solomon (2008) found that MW-27
and MW-19 showed the influence of young water and commented that the outer margin of the
groundwater mound must be between MW-27 and MW-30 and MW-31 which contain water that
has no tritium and is therefore older than mid-sixties atomic testing (see Figure 22 for the
locations of existing monitoring wells at the site). They state:
"Several samples have tritiogenic helium-3, indicative of young woter, however
these are only found in areas influenced by the wildlife ponds (MW-19, and MW-
27). Tritiated water is introduced into the system by recharge from the wildlife
ponds and appears in wells around the wildlift ponds. As recharge water from the
wildlife ponds propagates through the system, evidence of tritiated water will
appear in successive monitoring wells further from the ponds. "
And:
"Furthermore, stoble isotopefingerprints of 6D and 6t8O suggest mixing between
wildlife pond recharge and older groundwater in MW-19 and MW-27. 6345-SO4
and 618O-SO4 fingerprints closely relate MW-27 to wildlife pond water, while the
exceptionally low concentration of sulfate in MW-27, the only groundwater site to
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exhibit sulfate levels below 100 mg/L, suggest no leachatefrom the tailings cells
has reached the well."
Thus, according to Hurst and Solomon (2008), tritium data from wells in the area of highest
nitrate would contain younger water (the CFC dates for groundwater in MW-27 range from 1963
to 2001). However, they have already proven that groundwater in this area could not have come
from the tailings impoundments.
1.5 Mass Balance Calculations
It is possible to estimate the mass of nitrate and chloride in the groundwater beneath the mill site
by assuming a saturated thickness of groundwater in the aquifer matrix, a porosity of the aquifer
matrix, an average concentration of constituents in groundwater, and an area to which the
average concentration applies. Any potential source of nitrate and chloride will be evaluated to
determine if it has the potential to have caused the mass of nitrate and chloride observed in the
groundwater plume beneath the mill site. First, the potential source must have a means to reach
groundwater such as sufficient water or other fluid to travel through the vadose zone. Second
there must have been suffrcient nitrate and chloride in the source to account for the nitrate and
chloride mass observed in the groundwater. Both conditions can be evaluated by mass balance
calculations. This work will support a synthesis of all data collected in previous studies and will
be instituted when all previous work is complete, approximately eight months after approval of
this document (Table 1). This study is described in more detail in Section 8.0 of this document.
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2.4 GEOLOGY AND HYDROGEOLOGY
The Site is located on White Mesa about 6 miles south of Blanding, Utah (Figure 5). Figwe 22
shows the locations of existing monitoring wells at the site. The geologic layers beneath the Site
consist of four main units. The surface and shallow alluvium consists of unconsolidated silt and
sand to a depth of approximately 20 feet (22 ft in monitoring well MW-27). The alluvium is
underlain by Cretaceous and Jurassic bedrock as follows, from youngest to oldest: the Upper
Cretaceous Dakota Formation sandstone, siltstone, mudstone and shale, the Lower Cretaceous
Burro Canyon sandstone, mudstone, and claystone, and the Upper Jurassic Brushy Basin
Member of the Morrison Formation mudstone, claystone, shale, and sandstone. The top of the
unconfined water table is located at a depth of 50 to 60 feet below ground surface (bgs) and the
base of the aquifer is at the contact between the base of the Burro Canyon Formation and the top
of the Brushy Basin Member, about 90 feet bgs. Thus the aquifer thickness is about 30 feet, with
an average gradient (i) of about 0.011 from north to south across the Site (14,400 ft from wells
TWN-12 to MW-20, water level elevations from May, 2008). The gradient increases to nearly
0.02 near the wildlife ponds where groundwater mounding occurs. According to Kirby (2008),
the porosity (n) for undifferentiated Dakota and Burro Canyon Formation ranges from 2 to 22
percent, with a mean value of 10 percent. Hydraulic conductivity (K) of the aquifer based on
laboratory measurement had a mean of 0.32 ftlday (1.14 x 10-4 cm/sec). Using the mean K,
mean n, and site groundwater gradient i, the average groundwater velocity across the site is
calculated as follows: V-average = il(/n = 0.035 ff/d x 360 = 13 ftlyr. Thus, based on the
published. regional aquifer parameters and local gradient, it would take approximately 1,100
years for water to travel 14,400 ft from wells TWN-12 to MW-20. On-site aquifer testing
indicates a range of groundwater velocities from 0.55 ff/yr to 7 ftlyr in the northeast part of the
site, to 23 ftlyr in the mill area (Hydro Geo Chem, frc., 2009). Using the higher value of 23
ftlyear, it would take approximately 626 years for groundwater to travel from well TWN-12 to
well MW-20.
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3.0 PROJEGT MANAGEMENT
This project is managed by Dr. Dan Erskine of INTERA, Inc, Albuquerque, New Mexico. The
field program will be conducted under the direction of Robert Sengebush of INTERA, utilizing
INTERA field staff in cooperation with the DUSA White Mesa mill management and field
personnel. Subcontractors, such as geoprobe operators and drillers, will be under contract to and
under the supervision of NTERA.
3.1 FieldDocumentation
Field documentation will consist of a detailed field note book and digital photographs. tn
addition, the locations of geoprobe borings and other field activities will be recorded using a
hand held global positioning system (GPS) instrument.
3.2 Health and Safety
An INTERA health and safety plan (HASP) will be prepared to address the health and safety
requirements of all tasks outlined in this work plan. In addition, White Mesa mill health and
safety and radiation protection procedures will be followed. Health and safety tail gate meetings
will be held before starting field work and will address the specific requirements of the tasks
scheduled to be conducted that day. All health and safety protocols and meetings will be under
the supervision of and coordinated with the DUSA White Mesa mill Radiation Safety Officer
and health and safety manager.
The following sections of this work plan describe the specific tasks to be conducted by INTERA
on behalf of DUSA in an effort to identify the source of nitrate in groundwater beneath the site.
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4.0 HISTORICAL LAND USE AND GEOTORPHOLOGIC STUDY
Historic land uses at and in the vicinity of the site were evaluated in the Source Review Report,
which was submitted with the CIR. INTERA Performed a preliminary evaluation of additional
historical land uses in the vicinity of the White Mesa Mill property (site) to (1) identify areas that
have been subject to agricultural activities and (2) evaluate land-use practices that may have led
to elevated levels of nitrate and other contaminants in groundwater. Objective (1) is also
required to identify areas for sampling of buildup of atmospheric nitrogen, since we seek to
sample areas that have not been subject to anthropomorphic activities. For this analysis, we
evaluated historical aerial photography, historical Landsat satellite imagery, and performed a
brief lnternet-based search of historic military activities in the region.
Further evaluation using additional imagery and further investigation of military uses of the site
will be ongoing due to discovery during the preliminary evaluation that the mill site had been
previously used as a part of the Pershing Missile Project, Blanding Launch Complex.
1.1 lnifial Procedurc
INTERA acquired historical aerial photography for the site from 1937,1955, 1997,2006, and
2009. We acquired Landsat imagery from 1985. These images are presented in Figures 6
through 1 1. Outlines of the primary White Mesa Mill features are provided on each image for
reference. Note that the 1985 Landsat image is somewhat bluny due to the fact that Landsat
images pixels are approximately 100 feet (30m) on a side. While the Landsat.image does not
provide significant detail, it does provide a useful tool for identifying areas of irrigated
agriculture and riparian vegetation, which show quite clearly as areas that are much greener than
the surrounding landscape.
These specific images were acquired because they were the most readily available and were
available quickly for our analysis. More imagery is available and is being acquired, but will
require some weeks to receive from various archives. However, the imagery that has been
acquired to date allows us to make some preliminary conclusions with respect to historical land
use, and may be supplemented with some additional analyses in the future.
The imagery was analyzed visually primarily for color and texture. Areas of pasture are clearly
visible in the 1937 and 1955 photos as areas of relatively constant color and texture that stand
out from surrounding areas not influenced by anthropomorphic activities. In the 1937 photo, the
pasture areas generally appear as bright white patches. This is a corlmon appearance for
agricultural lands in early photography from the 1930s, because of the high contrast of the
photography. The 1955 photo shows the pasture areas even more clearly, and the quality of the
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photo allows for more detailed analysis. For example, close inspection reveals that the three-
pronged pasture area present in the southwestem corner of Figure 7 is shaped the way that it is
because the linear stretches of pasture are each coincident with a drainage that would be
expected to provide slightly more water to the pasture grass (Figure l2). Figure 12 clearly shows
a set of three drainages, each of which is coincident with a "finger" of pasture. Figure I 3 shows
the pasture outline overlain onto the United States Geological Survey (USGS) 7.5-minute
quadrangle topographic map for the area, and the drainages are clearly visible on the map, as is
the stock pond that they empty into in the central portion of the pasture. Figure 14, from 2006,
indicates that the stock pond has been in use continually into recent times.
Using this same logic, and interpreting land use visually based on texture and color primarily
from the 1955 photo (which provides the clearest view, based on present data, of historical
agricultural activity in the vicinity of the site), we identified and digitized obvious pasture areas
(Figure 15).
As discussed above, we also performed a brief Internet-based search of historic military activity
in the vicinity of the site. The Blanding, Utah area was used by the United States Army from
1963 to 1970 as a launch site for Pershing missiles, which were flown to White Sands Missile
Range in New Mexico (Encyclopedia Astronautica, 20lla). Black Mesa (ust west of White
Mesa, Figure 16) was one of numerous suborbital launch sites used to test the Pershing and other
missile systems (Encyclopedia Astronautica, 201lb). While some of the historical information
that we have discovered thus far indicates that primary launch operations were on Black Mesa,
other information that we have'discovered indicates that support operations such as radar
tracking (Figure 17) and other substantial support activities, even perhaps launches themselves,
occurred at and near the mill site on White Mesa (Figure 18). While these historical photographs
provide only preliminary information, they certainly indicate the strong potential for military
operations on White Mesa that may have led to some or all of the observed present-day
groundwater contamination problems.
4.2 lnitial Conclusions and Recomrnendatlons
INTERA evaluated historical aerial photography to identify areas that have been used in the past
for grazing or other agricultural activities. These areas were identified for two reasons: (1) to
evaluate areas that may have contributed to nitrate or other contaminants in groundwater due to
agricultural operations and (2) to identify areas that have not been influenced by
anthropomorphic activities during recent historical times, to allow identification of potential
sampling areas for evaluation of natural atmospheric accumulation of nitrates.
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The results from a preliminary analysis of readily-available aerial photography allowed us to
clearly delineate areas in the vicinity of the White Mesa Mill that have been used as pasture in
the past. These areas were digitized and the resulting polygons can be overlain over present-day
aerial photography and mapping data to evaluate them as potential sources of groundwater
contamination as well as identify sampling locations for the atmospheric nitrogen study.
Additional historical aerial imagery is being acquired, and review of this additional information
is being conducted.
With respect to researching historical military operations in the vicinity of the White Mesa Mill,
we have completed a very preliminary search which indicates that the US Army had operations
on White Mesa associated with launch testing of the Pershing missile dating from the early
1960s through about 1970. These activities certainly deserve additional analysis as they have
significant potential to have had soil and groundwater contamination associated with them.
Additional research is underway to more fully evaluate these activities.
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5.0 INVESTIGATION OF NATURALLY OGCURRING NITRATE
RESERVOIR IN SOIL
The purpose of this investigation is to test for the presence or absence of a nitrate and chloride
concentration in the alluvial soil column in selected locations at the Site. The Site and the DUSA
property boundary are shown on Figure 19. Such concentrations or "reservoirs" have been
identified in the scientific literature (Walvoord, et al., 2003, Scanlon, et al., 2005 and others).
"Unsaturated-zone chloride and nitrate profiles archive changes in recharge related to recent
conversion of rangeland to agricultural ecosystems. Increased recharge associated with dryland
as well as irrigated agriculture can lead to degradation of groundwater quality because of
leaching of salts that have been accumulating in the unsaturated zone for thousands of years prior
to cultivation, because of application of fertilizers, and, in irrigated areas, because of evapo-
concentration of applied groundwater. In the SHP (southem high plains), median groundwater
nitrate-N concentrations increased by 221% beneath irrigated areas and 163% beneath dryland
areas, reflecting LUllC-induced (land use/land cover) contamination of groundwater." (Scanlon,
et al., 2005).
This investigation will involve geoprobe borings to test nitrate and chloride concentrations in the
alluvial soil, and drilling rock core in several locations.
Based on the results of the historical land use and geomorphologic study, the boring locations
have been chosen to represent areas which have not undergone irrigation or other forms of
culturally-induced surface water recharge. These'locations are based on interpretation of aerial
photographic imagery. Actual locations will be selected in the field by the field team leader in
consultation with DUSA management and field personnel. This selection process is designed to
maximize the opportunity of finding soil chemistry that reflects only natural cycles of wetting
and drying from precipitation and evapotranspiration. The presence of such a nitrate and chloride
reservoir would suggest that these concentrations could be present throughout the White Mesa
alluvial soil column and could be mobilized to groundwater as the result of increased surface
water recharge due to irrigation, surface water impoundment, canal leakage, or other recharge
processes.
Scanlon (2005) shows nitrate concentrations in soil on Texas high plains rangeland on the order
of 200 mdL at depths between approximately 9 and 19 ft bgs, and up to over 300 mg/L in
irrigated high plains soil at approximately 3 ft and a nitrate spike of about 190 mg/L in high
plains dry land farming soil. The thickness of the elevated nitrate mound or spike is on the order
of 6 ft. The non-elevated nitrate and chloride concentrations are on the order of l0 mg/L or less.
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5.1 Geoprobe Nitrate and Chloride lnvestigation
The purpose of the geoprobe investigation is to determine the presence or absence of a soil
nitrate and/or chloride reservoir in the alluvial soil. The following procedure is written to apply
to both nitrate and chloride, although only nitrate procedures are described from this point
forward. The investigation will consist of 20 selected locations spread across the entire DUSA
mill property. At each location, an initial boring (with no sampling) may be conducted to test
subsurface conditions and one probe boring will be conducted for sample collection. Based on a
log of monitoring well MW-27 , the thickness of the alluvial cover near the center of the mill site
is approximately 22 feet. The field team will be prepared to test the entire interval from ground
surface to the top of bedrock or geoprobe refusal (whichever is first) in one foot increments. The
location latitude and longitude of these geoprobe borings will have been recorded prior to
conducting the field work.
The geoprobe boring locations are shown on Figure 20. These locations are approximate and
may be changed based on judgment of the field team leader in consultation with DUSA
personnel. The actual "as built" location of each boring will be recorded in the freld with a hand
held GPS instrument.
The geoprobe boring naming protocol is as follows:
GP-XX, where GP stands for geoprobe and XX is the number of the location, as 01, 02,12, etc.
The geoprobe boring locations will be recorded in the field note book as follows:
Boring ID Longitude
The geoprobe boring samples will be collected using the following methods:
1.Set up the geoprobe in the pre-selected location using a map and GPS. Create a labeled
GPS waypoint for the "as built" location.
Collect a soil sample from 0.5 ft bgs and test for nitrate and chloride according to the
field test procedures described below. The total sample volume should fill a one quart
sealable plastic bag. This is the "background" or "baseline" sample for this location. This
sample will be designated as GP-XX-BKG.
Probe to refusal to determine subsurface soil conditions and the depth to the top of
bedrock (Dakota Formation or Burro Canyon Formation). This is a non-sampling
geoprobe boring and is optional, at the discretion of the field team leader.
4. Probe and obtain a continuous soil core from surface to total depth in one geoprobe
boring.
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Measure and mark depth in I foot increments on the boring core sleeve. This is adequate
sampling interval resolution to identify elevated nitrate or chloride concentrations on the
order of 6 ft thick (Scanlon, 2005).
Open the sleeve to observe and describe the alluvial texture and/or lithology. Describe or
log the soil texture based on the Unified Soil Classification System (USCS).
Place the soil from each one-foot increment into a sealable plastic bag. Mix the soil
thoroughly in the plastic bag by gently inverting the bag multiple times. The purpose of
this procedure is to thoroughly blend the soil so that a sample aliquot from the bag will be
representative of the entire one-foot interval. Seal the plastic bag, label and store for
additional analysis in the event the interval contains elevated nitrate and/or chloride.
Select a sample aliquot from the bag and test for nitrate using the nitrate field test kit test
strips. This entails mixing a volume of soil with a volume of double distilled water
(prepared by the laboratory) to create a liquid extract. Test the liquid extract with the
nitrate test strip. Follow the test strip manufacturer's and USDA Natural Resource
Conservation Service instructions, attached to this work plan, Appendix A. Note that the
test strip maximum concentration is 50 mg/L.If the test strip reads 50 mg/L, perform a
dilution to determine the actual concentration, according to instructions in Appendix A.
Record the test results in the field notebook.
10. If any of the soil column analyses indicate the presence of elevated nitrate, select the
balalrce of that interval sample and place in a second, labelpd sealable plastic bag (double
bag) for delivery to the analytical laboratory for analysis of nitrate and chloride by
synthetic precipitation leaching procedure (SPLP) method. "Elevated" concentrations are
defined as those I foot intervals with nitrate concentrations at least twice the average
background concentration, based on field analysis of a sample 0.5 ft below ground
surface. Analytical methods for soil analysis are listed for Hall Environmental Analytical
Laboratory (HEAL) (Appendix B). Handle, package,label, fill out chain-or-custody, and
deliver the samples according to the soil sampling and handling procedures.
I l. Collect a sample from the bottom of the boring, regardless of whether it tests positive for
nitrate, and package in a double bag for delivery to the laboratory and analysis for nitrate
and chloride by the SPLP. Also collect one sample for SPLP from an interval which lacks
evidence of elevated nitrate, as a baseline analysis.
12. Discard the remaining bagged soil on the location and dispose of the plastic bags.
13. Fill the boring with dry bentonite material to seal the boring and restore surface location.
14. Move to the next location.
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15. For the purpose of cost estimation, assume 15 test kit analyses per boring and four (4)
SPLP analyses for nitrate and chloride per sampling location.
16. The core hole borings will be back filled with cement/bentonite grout after drilling. The
location of actual boring location will be recorded with a hand-held GPS instrument for
plotting on the map and for future reference.
17. Assess results with management.
5.2 Goring Study to Explore for Natural Nitrate Reservoir
This task consists of advancing a drill hole through the alluvial material and then drilling a rock
core of the formation beneath the alluvium, in up to four potential nitrate reservoir locations that
are shown to contain elevated nitrate in the soil column within the geoprobe soil samples. The
definition of "elevated" is a nitrate concentration at least twice background, based on the
concentration of nitrate in near-surface soil samples, as described in Section 5.1. The purpose of
this work is to trace the nitrate from the base of the alluvium and into the bedrock column
(Dakota Formation and upper Burro Canyon Formation) to the water table.
The coring will be conducted with a conventional truck-mounted drill rig using a combination of
hollow stem auger and air rotary methods, without introducing water or other drilling fluids into
the borehole.
Using monitoring well MW-31 as an example, the subsurface layers are expected as follows:
Alluvium: 0-22ftbgs (op of bedrock -22 ftbgs)
Depth to Groundwater (2009, approximate):77 ft bgs
Length from top of bedrock to groundwater: J7 - 22 = 55 ft
Therefore, the length of core drilling in this example is 55 ft.
The entire core interval will be boxed and logged (described) according to standard geologic
methods.
Three one foot core intervals will be collected from the interval between the base of the alluvium
and the groundwater table, including the core located at the top of the water table. The three
cores will be evenly spaced within the distance between the alluvium and the water table. For
example, if the top of bedrock is22 ft bgs, the water table is at77 ft bgs, and the interval from
the top of bedrock to the water table is 55 ft, the three cores will be as follows: the top core (from
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22 - 23 ft), the middle core (22 + 27 ft = 49 -50 ft) and the bottom core (49 + 27 = 76-77 ft,
approximately).
No field testing will be conducted on these rock cores. The one-foot core intervals will be
packaged and shipped to a State of Utah certified analytical laboratory for analysis of the
presence of nitrate and chloride in the rock cores by the SPLP analysis method. The laboratory
will need to crush, pulverize, and blend the rock core material, and measure the pore moisture,
before conducting the analysis. Each analysis will be considered representative of the entire one
foot interval.
The core hole borings will be backfilled with bentonite grout after drilling. The as-built boring
locations will be recorded with a hand-held GPS instrument for plotting on the site map and for
future reference in the field.
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6.0 INVESTIGATION OF POTENTIAL NITRATE SOURCE LOGATIONS
This investigation combines an initial geoprobe investigation of potential nitrate and chloride
sources, followed by bedrock coring if positive results for nitrate and chloride are encountered
during geoprobing.
6.1 Geoprobe lnvestigation of Potential Nitrate Source Locations
The purpose of this investigation of potential nitrate and chloride source locations is to assess the
presence or absence of elevated nitrate and chloride concentrations in the alluvial layer (above
bedrock) in locations where past or ongoing activities may have contributed nitrate and/or
chloride to the soil and/or groundwater. Specifically, the purpose is to test whether nitrate and
chloride residues can be found in alluvial soils or at the alluvial bedrock interface. The alluvial
bedrock interface marks a change in porosity and permeability and is judged to be the most likely
location to find nitrate and chloride residues from potential sources that found a pathway to
groundwater.
The potential nitrate source locations include up to seven (7) leach fields, as well as other
installations such as ammonia tanks, a sewage vault, andLawzy Lake, a former pond that may
have held contaminated water. The investigation of these potential sources is contingent on
access with the geoprobe rig and subject to approval by DUSA management, based primarily on
field team health and safety considerations. The subsurface configuration or design of the leach
fields, including the potential for underground piping, is not known. Any excavation or borings
in these leach fields will require prior identification of underground structures, such as piping,
septic tanks, or vaults, using techniques such as air knife or equivalent "daylighting" methods.
Design drawings and records will be reviewed prior to work and the borings will only be
attempted with the full approval of DUSA management.
The leach field locations and dates of operation listed below are provided by DUSA management
and are shown on Figure 2l:
Potential Nitrate Source Locations
Main leach field (also known as Leach Field east of Scalehouse, 1985 to present)
Sewage vault/lift station
Scale house leach field, (also known as Leach Field south of Scalehouse,l9TT-1979)
Former office leach field
Ammonia tanks
1.
2.
J.
4.
5.
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6. SAG leach field (Leach Field north of mill building, 1998 to 2009)
7. Cell 1 leach field (Leach Field east of Cell #1, up to 1985)
8. Fly ash pond
9. Chlorate tanks
10. Ammonium sulfate crystal tanks
ll.Lawzy sump
12.LawzyLake
13. Former vault/lift station (to Former Office Leach Field) (1992 to 2009)
14. Truck shop leach field(1979-1985)
15. Counter Current Decant/Sovent Extraction (CCD/SX) leach field
Note that locations 1 and 15 are known to be in use at present. For these locations, optional
source influent sampling and analysis may be conducted instead of subsurface soil sampling and
field testing. Conducting borings in the active leach fields is not recommended due to the
potential to create a pathway for the waste water fluids from the leach field down to the
groundwater table. As an alternative, water samples will be collected from influent piping (if
possible) near the operating leach field, downstream of the septic tank (if present) that is
designed to collect solids. It is not known at this time if such influent piping will be accessible. .
These waste water influent samples, if any, will be analyzed for nitrate and chloride by the
methods shown in Table 2 of this work plan. Sampling and analysis of raw wastewater influent is
described in detail in the publication, "Influent Constituent Characteristics of the Modern Waste
Stream from Single Sources." (Lowe, et al., 2009). As a point of reference, the average
concentration of nitrate in raw waste water from single sources is 2.1 mglL (Lowe, et a1.,2009).
If waste water is sampled, it will be analyzed for nitrate and chloride and a mass balance
calculation will be performed to determine if the influent source could create the level of nitrate
concentrations found currently in groundwater beneath the site.
The following tasks will be conducted on the locations listed above (except for the two leach
fields known to be currently in use):
1. If approved by DUSA management, conduct test geoprobe boring (without core sleeve)
to refusal to determine alluvial thickness and evaluate subsurface conditions. If
subsurface conditions are deemed safe for boring and sampling, proceed as described
below.
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2. Conduct geoprobe boring with core sleeve to collect soil core through alluvial interval.
3. Collect 6-inch core sample from two intervals within the alluvial interval and one 6-inch
core sample from the base of the alluvial interval, at the contact with the bedrock
formation.
4. Place the soil material in double, sealable plastic bags and label.
5. Collect an aliquot of the material and test with the nitrate field test kit according to the
procedures described in Appendix A.
6. For samples with positive results from the field test kit analysis, handle, pack, and ship to
the laboratory, with chain-of-custody, per standard operating procedures.
7. Backfill the geoprobe boring with bentonite to seal the hole.
8. Thoroughly clean the geoprobe drill pipe and other equipment between locations.
9. Analyze for the following, in soil:
a. Nitrate
b. Chloride
O 6.2 Goring Study in Potential Nitrate Source Locations
This task consists of advancing a drill hole through the alluvial material and then drilling a rock
core of the geologic formation beneath the alluvium, in up to 13 potential nitrate source locations
' that are shown to contain elevated nitrate in the soil column within the geoprobe soil samples.
These 13 locations are the locations which have been identified as possible nitrate source areas
but are not the locations of the two active leach fields at locations I and 6. The procedures for
conducting this core drilling and sampling are identical to those described in Section 5.2.
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7.0 STABLE ISOTOPES STUDY
The purpose of the stable isotope study is to identify the source of the nitrate in the groundwater
beneath the site.
Stable (non-radioactive) isotopes are elements that have the same name (i.e. oxygen, nitrogen,
carbon, etc.) but differ by the number of neutrons in the atomic nucleus. Physical and biological
processes can affect the relative concentrations of light and heavy isotopes of the same element.
This relative enrichment or depletion of one stable isotope over another is called isotopic
fractionation. During evaporation of water, for example, the heavier '8O becomes enriched in the
residual water as more of the lighter 160 enters the vapor phase. Thus, meteoric water, derived
largely from the evaporation of ocean water, is enriched in 160 relative to ocean water.
Biological organisms preferentially use laN, rather than lsN, for respiration and assimilation
because the chemical bonds of lighter isotopes are generally broken more easily than those of
heavier isotopes. 'oN b.comes concentrated in cell mass while ttN becomes concentrated in the
residual nitrogen source and in human and animal wastes. In addition, a disproportionate amount
of laN as compared to lsN is released to the atmosphere during ammonia volatilization from
human and animal waste, fostering enrichment of lsN. Thus, nitrate in groundwater that has been
denitrified by microbes, or originates from human and animal waste, is enriched with l5N. These
isotope fractionations have long been studied to trace flow paths and mixing of water sources,
and to identify sources of nitrate and ammonia in groundwater. Isotopic compositions are usually
presbnted as delta values (e.g., 6lsN), which express the ratio of the heavy to light isotopes (i.e.,
2HllH, 'sN/'aN, and 180/160), relative to a universal standard.
Figure 2 shows 5l5N results from sampling of various sources of nitrate contamination, including
a uranium mill, from McQuillan et al (1989), showing the potential to exclude mill tailings as a
source of nitrate in groundwater, depending on the 6l5N signature in the groundwater.
However, Figure 3 shows 6lsN results normalized to N2 in the atmosphere from sampling a
different set of sources indicating the complexity that could potentially be encountered, raising
the possibility that, while some sources can be readily distinguishable, results of any isotopic
study could be inconclusive for distinguishing other sources.
Finally, Figure 4 is a plot of 6180 versus 6r5N from Roadcap et al (2001), also showing the
overlapping nature of various sources but displaying the additional power of adding 6180. Hurst
and Solomon (2008) used Deuterium and 6180 values to fingerprint groundwater sources during
their study at White Mesa and it was part of their evidence that young water in MW-27 and MW-
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19 was coming from the wildlife ponds (see Figure 22 for the locations of existing monitoring
wells at the site).
The possible nitrate sources at the site include nitrate in waste water (in leach fields), nitrate-
fertllizer, ammonium nitrate and other nitrate-producing compounds from historical missile
launch activity, and/or a naturally occurring nitrate reservoir in soil. The only potential pathway
on the site from the surface to groundwater that is known at this time is the surface water in the
wildlife ponds and some other nearby stockponds. Other sources could include historic stock
ponds, possible deep disposal wells operated by historic users of the site, leach fields or other
installations where continuous head and soil moisture is created from the surface to groundwater
and a demonstrated connection between surface water and groundwater on the site could point to
a possible connection between a nitrate/chloride source in that surface water and the current
elevated nitrate and chloride concentrations in groundwater.
Previous sampling and analysis for stable isotopes in groundwater was conducted by the
Department of Geology and Geophysics, University of Utah, and documented in the report
"summary of work completed, data results, interpretations and recommendations for the July,
2007 Sampling Event at Denison Mines, USA, White Mesa Uranium Mill Near Blanding, Utah
(Hurst, G.T., and Solomon, D.K., 2008) prepared on behalf of the Utah Division of Radiation
Control (DRC). The stable isotopes measured for the DRC study were tritium, tritogenic helium-
3, deuterium, 'tO, "N, and 3aS.
The DRC report concludes the following: "6345 and 618O isotopic signatures on dissolved sulfate
provide distinction between surface water sites and monitoring wells. The tailings cells and
wildlife ponds exhibit significantly enriched 6180-50+ values relative to monitoring wells, and
depleted 63as-So+values relative to monitoring wells. MW-27 (see Figure 22) is the only
monitoring well to bear an isotopic fingerprint closely related to that of the surface water sites,
suggesting recharge from the wildlife ponds has reached MW-27 and funher evidence that the
wildlife ponds are providing recharge to the aquifer. Sites with high concentrations of metals
(MW-3, MW-14 shallow and deep, MW-15, MW-18, and MW-22) bear very different isotopic
fingerprints than those of the surface water sites. In general, the data collected in this study do
not provide evidence that tailings cell leakage is leading to contamination of groundwater in the
area around the White Mesa mill. Evidence of old water in the majority of wells, and
significantly different isotopic fingerprints between wells with the highest concentrations of trace
metals and surface water sites, supports this conclusion. The only evidence linking surface
waters to recharging groundwater is seen in MW-27 and MW-19. Measurable tritium and CFC
concentrations indicate relative young water, with low concentrations of selenium, manganese,
and uranium. Furthermore, stable isotope fingerprints of 6D and 6180 suggest mixing between
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wildlife pond recharge and older groundwater in MW-19 (north of northern wildlife pond) and
M.W-27 (west of southem wildlife pond, at NE corner of tailings cell no. 1). 534S-SOa and 6180-
SOa fingerprints closely relate MW-27 to wildlife pond water, while the exceptionally low
concentration of sulfate in MW-27, the only groundwater site to exhibit sulfate levels below 100
rnglL, suggest no leachate from the tailings cells has reached the well." (Hurst and Solomon,
2008, p. 59). "The southern margin of artificial recharge is likely to be between MW-27 and
MW-31 while the northern margin appears to be between MW-18 and MW-19." (Hurst and
Solomon, 2008, p. 27).The Hurst and Solomon study documents that the tailings cells are not
discharging to groundwater and thus, the tailings cell fluids are not the nitrate source.
By established convention, isotopic ratios are defined as delta (6) values, which are obtained by
the equation:
6 (isotope) = {[R(sample) - R(standard)]iR(standard)] -l (1,000).
Where: 6 (isotope) = values in per thousand (%o) or per mil and R(sample) = 11r. ratio of the first
and second isotope such as '80/'60, and R(standard) = the ratio of 180/160 used in international
or other standards. For example, the standard for 180/160 is Standard Mean Ocean Water
(SMOW). A positive (+) 6 value indicates that the heavier isotope 1i.e., 18O; in the sample is
enriched when compared to the standard. A negative (-) value indicates that the sample has more
of the lighter 1160) isotope. The International Atomic Energy Agency (IAEA) and the National
Institute of Standards and Technology (NIST) have established and published these standards.
The wells to sample for stable isotopes in groundwater are as follows urd ur. shown on Figure
22:
o MW-20
o MW-31
o TWN-I9
o TWN-2
o TWN-9
o TWN-I7
The proposed stable isotope and other analyses for these groundwater samples are as follows:
o nitrate + nitrite
o total Kjeldal nitrogen
o chloride
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. 6l8O*ut", &od 6D*"t", (D = 2H, Deuterium)
The groundwater sampling and analysis procedures are described in the DUSA Quality
Assurance Project Plan (QAPP) and on Table 2 of this Work Plan. The stable isotope
groundwater samples will be collected during the regularly scheduled quarterly groundwater
sampling event conducted by the Site water sampling team.
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SlProiects\luc-oo1-01-oo1 Denison Mines\2olowirab Besposeuwod( Pla\wolt Plil and Schedule ror suppptementa CIR RgV 3.dOCX
February 14,2011
::=ra=MiFil*-E
8.0 MASS BALANCE CALCUI.ATIONS
It is possible to estimate the mass of nitrate and chloride in the groundwater beneath the mill site
by assuming a saturated thickness, of groundwater in the aquifer matrix, a porosity of the aquifer
matrix, an average concentration of constituents in groundwater, and an area to which the
average concentration applies. Any potential source of nitrate and chloride will be evaluated to
determine if it has the potential to have caused the mass of nitrate and chloride observed in the
groundwater plume beneath the mill site. First, the potential source must have a means to reach
groundwater such as sufficient water or other fluid to travel through the vadose zone. Second
there must have been sufficient nitrate and chloride in the source to account for the nitrate and
chloride mass observed in the groundwater. Both conditions can be evaluated by mass balance
calculations.
An example of these mass balance calculations was presented in the December 30, 2009 CIR
where one of the suggested possibilities was a groundwater mound from the tailings cells that
might cause elevated nitrate and chloride concentrations upgradient in the area of the nitrate and
chloride plume. A calculation for nitrate to evaluate this possibility (a calculation for chloride
would be similar) suggests that on the order of eleven percent tailings solution (assuming the
highest recently observed nitrate concentration in the tailings of 290 mglL) would have to mix
with unimpacted groundwater (assuming I mg/L) in order to account for the observed mass of
nitrate in groundwater, assuming an average nitrate concentration in the plume above the 20
mg/L isopleth of 30 mg/L
The size of the nitrate plume above 20 mglL is approximately 40 acres, or 1,800,000 square feet
in map area. Assuming 45 feet of saturation (Chloroform Investigation Report) and a porosity of
0.2, there are 16,200,000 cubic feet or 121,176,000 gallons of groundwater in that area. Eleven
percent of that is 13,329,360 gallons (approximately 4l acre feet) which is a conservative
estimate of the volume of tailings solution that would have to be mixed with groundwater to
account for the mass of nitrate in the portion of the plume above 20 mglL nitrate.
Assume:
o Nitrate Concentration in Tailings Solution 290 mglL
o Nitrate Concentration in un-impacted Groundwater I mg/L
o Average Plume Concentration
Mixing Equation: C,*V, t Ce*Ve = C-*V.
Where: Ct = Concentration of nitrate in tailings solutions
Vt = Volume of tailings solutions
30 mg/L
(eq l)
Work Plan for Supplemental Contaminant lnvestigation Report
forWhite Mesa MillNitrate lnvestigation 24
SlpOects\lUC-OO1-O1 -OOl Oenison MinesUOl O\t,litrate Besponse\lwork Plan\Wort Plil md Schedule to( Suppplernental CIR RgV 3.dOCX
February 14,2011
ffiw
lnEE:IA:-r=
C, = Concentration of nitrate in unimpacted groundwater
V, = Volume of unimpacted groundwater
C,n = Concentration of nitrate in mixture of groundwater and tailings solutions
V, = Volume of mixture of groundwater and tailings solutions
Another Equation:
Substituting eq2 in eq1:
VttVe=V,n (eq 2)
C,*V, t Ce*Ve = C',* (Vt + VJ (eq 3)
Substitute Nitrate Concentrations in eq3
290*Vt + 1*Ve = 30x(Vt * Vr)
290*Vt + 1*Ve = 30*Vt + 30*Ve
260*Yr= 29*Ye
Yt=291260*Vs = 0.11*Vs
The volume of tailings solution would have to be eleven percent of the volume of un-impacted
groundwater in the mixture.
That amount of seepage from the tailings cells would certainly generate a groundwater mound.
Such a mound would have to be on the order of 5 feet on average over the entire 40 acres, but
would likely be much higher than that at the centroid of the plume and would taper off toward
the edges of the plume. However, no such mounding exists under the tailings cells. While
groundwater mounding can be observed towards the eastern portion of the site, away from the
tailings cells, it is clearly related to the wildlife ponds and not the tailings cells. As a final point,
if the concentration of nitrate in tailings documented in the Statement of Basis (24 mglL) were
used in the calculation, no amount of tailings solution would bring the plume concentration to 30
mglL.
Work Plan for Supplemental Contaminant lnvestigation Report
forWhite Mesa MillNitrate lnvestigation 25
StPOects\lUC-OO1-01-001 Denison Mines\2ol ov{itrate Response\lwort Plan\wort Plan and Schedule fo{ $ppplemordal CIR RgV 3.dOCX
February 14,2011
9.0 REFERENCES
Encyclopedia Astronautica,20l l, . http://www.astronautix.com/sites/blakmesa.htm.
Hurst, G.T., and Solomon, D.K., 2008, Hurst and Solomon,2008, Summary of work completed,
data results, interpretations and recommendations for the lluJy,2007 Sampling Event at
Denison Mines, USA, White Mesa Uranium Mill Near Blanding, Utah.
Hydro Geo Chem, Inc., 2009, Site Hydrogeology and Estimation of Groundwater Pore Velocities
in the Perched Zone White Mesa Uranium Mill Site Near Blanding, Utah
INTERA, Inc., 2009, Nitrate Concentration Investigation Report, White Mesa Mill Site,
Blanding, Utah.
Kirby, Stephen, 2008, Geologic and Hydrologic Characterization of the Dakota-Burro Canyon
Aquifer Near Blanding, San Juan County, Utah, Special Study I23,Utah Geological
Survey.
Lowe, Kathryn S., Maria B. Tucholke, Jill M. B. Tomaras, Kathleen Conn, Christiane Hoppe,
Jorg E. Drewes, John E. McCray, and Junko MunaKata-Marr. 2009.Influent Constituent
Characteristics of the Modern Waste Stream from Single Sources. Colorado School of
Mines, Environmental Science and Engineering Division, Golden, CO.
McQuillan, D.M., M.J. Jasper, and B.H. Swanson. 1989. Ground-water contamination by septic-
tank use: A field study in the Albuquerque South Valley-West Mesa region, Bernalillo
County, N.M. NMED Open-File Report EID/GWB-8912,37 p.
Roadcap, George S., Keith C. Hackley, Hue-Hwa Hwang, Thomas M. Johnson. 2001.
"Application of Nitrogen and Oxygen Isotopes to Identify Sources of Nitrates." [inois
Groundwater Consortium Conference, web publication,
www. siu. edu/worda/igclproceedings/0 1 /roadcap.pdf.
Scanlon, B.R., R.C. Reedy, D.A. Stonestrom, D.E. Prudic, and K.F. Dennehy. 2005, "Impact of
land use and land cover change on groundwater recharge and quality in the southwestem
LJS," in Global Change Biology, v. 11, 1577-1593.
U.S. Department of Agriculture (USDA), 2001, Soil Quality Test Kit Guide, Natural Resources
Conservation Service, Soil Quality Institute, July.
Walvoord, M.A., F.M. Phillips, D.A. Stonestrom, R.D. Evans, P.C. Hartsough, B.D. Newman,
and R.G. Striegl, 2003, 'oA Reservoir of Nitrate Beneath Desert Soils," in Science, v.302,
t02t-1024.
Work Plan for Supplemental Contaminant lnvestigation Report
forWhite Mesa MillNitrate lnvestigation 26 February 14,2011
siProjectsUUC-OO1-O'l -001 oenison Minesuolo[,,litrate Response\lwo* Plan\work Plan and Schedule for Suppplemenlal CIR ReV 3.dOCX
o
Figures
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Figure 4. A plot of 6180 vercus 6r5N
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synthetic
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Atmo*pherel
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Figure 3. 615N results normalized to N2 in the atmosphere from sampling a wider range of sources
S Prolects\lUC-CO l-01-001 Denison ltlines\GlSlnapdocs'2011 -\liP Nitrale Respcnsei2o1l012lRegina N,lap mxd
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Figure 6
Historical Aerial lmagery
1937 Aerial Photo
INEE?A
Figure 8
Historical Aerial lmagery
June 30, 1985 Landsat
S:\ProJecls\lUC-001-0'l-001 Derrison Mines\GlS\mapdocs\2010_AenallmageryResearch\Figure3_1985Aerial.mxd 1?.t28t201O
SoLrrce(s): 1997 7.5-Minute DOQQ County Mosarc,
U.S. Geological Survey
1.500 750 0 1,500
Legend
Site Feature
f""t
Figure 10
Historical Aerial lmagery
2006 DOQQ
-==MEE?A
=%SlProiects\lUC-001-01-001 DenisonN4ines\GlS\mapdocsu01o_AeriallmageryResearch\Figure5_2m6Aerial.mxd 122A12010
Figure 11
Historical Aerial lmagery
2009 DOQQ
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Figure 12. From the 1955 Photo Showing Pasture is Coincident with Drainages, which are Wetter
than the Surrounding Area
(A stock pond is visible near the center of the pasture area [yellow arrow]).
?l
Figure 13. Outline of 1955 Pasture Overlain over the USGS Topographic Map Showing Drainages
and a Stock Pond (Yellow Arrow) in the Central Portion of the Pasture
=HJ?dH*ffi
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Figure 14. 2006 Aerial Photograph Showing the Stock Pond
Figure 16. Location of Black Mesa relative to White Mesa
Figure 17. Radar Site at White Mesa near Blanding, Utah, June 21, 1967 (J.Willard Marriott
Library, University of Utah,2011)
=#ESrS
Figure 18. Bivouac Site at White Mesa near Blanding, Utah, June 21, 1967 (J. Willard Marriott
Library, University of Utah, 20ll)
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S:\Projects\lUC-001-01-001 Denrson Mrnes\GlS\n.rapdocs\2011_WP_Nitrate_Response\20110124SiteMap.mxd
Figure 20
Natural Nitrate Reservoir:
Geoprobe Boring Locations
Nitrate and Chloride
Source lnvestigation
S:\Projects\lUC-001{1-001 Denison Mines\GlS\mapdocs\2O11_WP_Nitrate_Response\j20110121ceoprobes.mxd
& Frog Pond approx. 1 mile NE
Wastewater Treatment Plant approx. 2 miles NE
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Ammonium Sulfate
Crystal Tanks [10]
V205 Mini Lab & V205 Precip
Truck Shop
1 979-1 985
Leach Field ['14]
Source(s) Aerlal - Utah GIS Portal website, dated 2009,
Wells - HGC, lnc., May 2008 report.
300 150 0 300
Feel
Leqend
Pipeline Piezometer
Potential Nitrate and Chloride Sources ,1', Spring/Seep
Leach Field (currently in operation) Surface Water
Leach Field - Geoprobe Boring *i, Chloroform Monitoring Well
and Core Drllling Location 0 Nitrate Monitoring Wella Monitorlng Well
Figure 21
Nitrate Source Areas:
Geoprobe Boring and
Core Drilling Locations
Nitrate and Chloride
Source lnvestigation
Former Vault [13]
1992-2009
Cell I Leach Field [7]
V205 Oxidation Tanks
Fly Ash Pond [8]
Ammonia Tanks [5]
Sewage Vault [2]
l, ri
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Nitrate data from September, October, or November of2009.A singie data point was used for each well. irXlt:(il.3ifr"l , ,rrfir3.i Portarwebsire, dared 2ooei
1,200 600 0 1,200
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Legend
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Groundwater Elevation Contour Piezometer' (interval 1o ft) a spring/Seep
Groundwater Elevation Contour
(interval 5 ft) ' Surface Water
Nitrate concentration (mg/L) + chloroform Monitoring well
Stable lsotope sampling well 0 Nitrate Monitoring well
Figure 22
Stable lsotope Sampling Wells
Nitrate and Chloride
Source lnvestigation
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Appendix A
Nitrate Extraction and Field Test Procedure
5. Electrical Conductivity Test
O ,oil samples for the electrical conductivity (EC) test are taken from the 0- to 3-inch depth. Bulked
soil samples from across the field can be collected, and two subsamples can be taken for analysis
(See Chapter 1, Sampling Guidelines). Electrical conductivity, pH, and soil nitrate are all
measured from the same soil subsample.
Materials needed to measure electrical conductivity (EC):
Did You l(now?
Excess salts in soil can be a
detriment to plant health. Salts
can also hamper water move-
ment into the soil and increase
the occurrence of surface com-
paction.
. 1/8-cup (30 mL) measuring scoop. 120-mL plastic containers with lid. EC pocket meter (blue with black cap). squirt bottle. calibration solution (0.01 M KCI). distilled water
O O Add water to Subsample and Mix
. Add 1/8-cup (30 mL) of distilled water to
the container with the subsample. The
resulting soiVwater mixture equates to a
1:1 soil to water ratio on a volume basis.. Put the lid on the container and shake
vigorously about 25 times.
@ Measure and Record EC (See Calibration Tip)
. Open the container and insert the EC pocket meter into the soil-water mixture. Take the
reading while the soil particles are still suspended in solution. To keep the soil particles
from settling, stir gently with the EC pocket meter. Do not immerse the meter above
the immersion level (See Appendix C, Figure 1c). Allow the reading to stabilize (stays
the same for about 10 seconds).. Enter the EC reading on the Soil Data worksheet in decisiemens per meter (dS/m). The
DiST WP 4 meter gives readings directly in dS/m. For the Microsensor 4 meter, divide
the reading by 10, and for the Microsensor 3 meter, divide the reading by 100 to get
readings in dS/m.. Save the soil-water mixture for the pH measurement (Chapter 6).
Ttrrn the meter off. Thoroughly rinse meter with distilled water and replace cap.
l4
Calibration Tip: Make sure the EC
meter is calibrated before
making a measurement.
See Appendix C for cali-
bration instructions.
C Extract Subsample
The soil sample should be thoroughly mixed before taking a subsample. Measure a 1/8-cup
level scoop subsample of soil and place it in the plastic container. If soil nitrates will be
measured on this subsample (Chapter 7), weigh the subsample for a more accurate estimate
of soil nitrates. Enter the subsample weight on the Soil Data worksheet.
O6
6. Soit pH Test
Use the same soil-water mixture prepared in the EC test to conduct the pH Test. If you are start-
ing with a fresh soil sample, read the introduction and follow Steps 1-3 in the EC Test Chapter
on preparing the sample.
Materials needed to measure pH:
1/8-cup (30 mL) measuring scoop
plastic specimen bottle
calibration buffer solutions
squirt bottle
pH pocket meter (red with black cap)
distilled water
Did You Know?
Soil acidification can also be an
indication of excessive N fertilizer
applications and N leaching loss.
Considerations: If the soil sample is saturated or very wet, a 1:1 ratio, on a volume basis, of soil
to water will not be obtained in the soil-water mixture (See Step 2, Chapter 5). Let the soil dry
before proceeding with Step 1 in Chapter 5. Also, a small amount of salts diffrrse out of the pocket
pH meter; therefore, EC measurements should always be taken first when measuring both EC
and pH on the same sample.
Measure and Record pH
. Make sure to periodically calibrate your pH meter (See Appendix C for instructions). If
the meter has not been used in a while, place the meter in tap water for about 5 minutes
before calibrating or taking a reading.
. Wait about 10 to 15 minutes after the EC measurement before measuring the pH. This
gives the soil particles time to settle. Insert the pH pocket meter into the topmost
portion of the solution and turn the meter on. Wait until the reading stabilizes (0-30
seconds), and record the digital reading on the Soil Data worksheet.
Rinse Pocket Meter
. Thoroughly rinse the electrode with distilled water.
. Store the electrode with a few drops of the pH 7 buffer solution and replace the cap.
(See Appendix C on storage of pH meter)
Maintenance Tips: Check the batteries
and calibrate the EC and
pH meters periodically.
Be sure to clean the
meters thoroughly to keep
them working properly.
15
7. Soil Nitrate Test (NO3-)
O ,r. the same sample prepared for the EC and pH tests to measure soil nitrates. If you are starting
with a fresh soil sample, read the introduction and follow Steps 1-3 in the EC Test Chapter on
preparing the sample.
Materials needed to measure soil nitrate:
Did You Know?
Soil nitrates are good measures of
plant-available nitrogen, but they
can be readily lost from the soil by
leaching and volatil ization.
Fold Filter
Fold the filter paper in half (into a semicircle).
Fold it again, but not quite into a quarter-circle.
Leave the edges a little uneven as in Figure 7.1
(A black line is drawn for demonstration purposes.)
Insert Filter Paper into Subsample
Open the filter paper into the shape of a cone and push
it (pointed part first) quickly into the jar with the
soiVwater mixture until it touches the bottom of the
jar @igure 7.2). Wait until about an eye dropper-
full of the solution has seeped through to the inside
of the filter paper. (Note: Inserting the filter
paper quickly prevents it from wetting up and
tearing as it is inserted.)
[For Steps 3 & 4, it would be helpful to lirst
familiarize yourself with the directions on the
side of the bottle of nitrate strips.l
Place Drops on Nitrate Strips
filter paper
120-mL plastic container with lid
eye dropper
nitrate/nitrite test strips
stopwatch or timer
distilled water
Oo
Figure 7.1
Figure 7.2
Using the eye dropper and one nitrate/nitrite test strip, place I or 2 &ops of the filtered
solution on each of the strip's two pads. Note the time.
NOTE: One pad measures the amount of nitrite, and the other measures the amount of
nitrite and nitrate combined. Nitrite rarely occurs in measurable amounts in soils, so nitrite
readings from the test strips are not recorded.
16
o @
Tr,;. #^,,:::,,P,h the bottom orthe bottre with your thumb corre-
sponding to the diagram on the bottle.
After 60 seconds, compare the first pad (fur-
thest from your thumb) along the nitr4lge scale
as shown in Figure 7.3. Estimate the nitrate
amount according to the degree of color change.
Enter the value from the nitrate scale on the Soil
Data worksheet in ppm. This value is an esti-
mate of nitrate-N concentration in the extract.
NOTE: The nitrate test strips have a shelf-life.
Check the expiration date on the bottle.
CALCULATIONS:
Figure 7.3
Estimated (lb NO3-N/acre) :
(ppm extract NOr-N) x (depth of soil sampled in cm) x bulk density x 0.89
10
Exact (lb NO3-N/acre):
(ppm NOr-N) x (volume water used) x (depth of soil sampled, cm) x bulk density x 0.89
(dry weight of soil) x 10
Volume water used: 30.0 mL + [dry weight of soil x soil water content (dg)]
Note: The maximum nitrate-N reading on the nitrate/nitrite test strip container is 50 ppm. If the
sample reading falls into the 50 ppm category the sample can be diluted to get a better estimate of
the actual amount over 50 ppm. To dilute the sample, fill the eye dropper with filtered solution and
place five drops in a plastic container. Add five drops of distilled water; mix gently by swirling the
container. Take a reading with a new test strip as stated in Step 4. Multiply the estimated nitrate-N
in ppm by 2 before using the calculations. If the nitrate reading falls into the category of 50 ppm
again, repeat the dilution steps, and multiply the estimated nitrate-N in ppm by 4.
Did You I(now?
Water samples may be taken from drinking water, well water, tile drainage, drainage
ditches, and ponds. Dip a nitrate/nitrite test strip into the water and estimate the nitrate or
nitrite concentration from the color chart on the test strip bottle. This test can give you an
idea of how much N fertilizer is lost from the soil. (See Chapter 12).
l7
Appendix B
Analytical Methods List
HALL
EI\TVIFIcIIUMEI\ITALAI\IAl.ysiIS
L/ABOHAItrIFlY
505.345.3975
Toll Free 888.546.0509
4gO1 Hawkins NE
Albuquenque, NM 87109
Receipt and Handling of Samples
Procedures
HEAL does not provide field sampling for any projects. Sample kits are prepared and provided
for clients upon request. The sample kits contain the appropriate sampling containers (with a
preservative when necessary), labels, blue ice, a cooler, chain-of-custody forms, plastic bags,
bubble wrap, and any special sampling instructions. The sample control manager reviews the kits
prior to shipment.
Containers
Containers which are sent out for sampling are purchased by HEAL from a commercial source.
Glass containers are certified "EPA Cleaned" QA level 1. Those containers are received with a
Certificate of Analysis verifying that the containers have been cleaned according to the EPA
wash procedure.
Preservation
If sampling for an analyte(s) requires preservation, the sample custodians fortify the containers
prior to shipment to the field. The required preservative is introduced into the vials in uniform
amounts and done so rapidly to minimize the risk of contamination. Vials that contain a
preservative are labeled appropriately.
The following contains tables specifuing additional preservation requirements for samples:
(Next Page)
Tables of Standard Holding Times, Preservation, and Containers
Organic Compounds
Purgeable halocarbons
:and aromatics
Purgeable halocarbons
and aromatics
iSemi-volatiles days to extract, 40
after extraction to
Semi-volatiles il4 days to extract, 40
ldays after exfiaction to
PCBs, pesticides,
2, or
pH<2;
14 days to analysis
4 days to analysis
ueous ll L amber lcool.4 o C
*Use of field methanol kits are available and recommended for the PSTB.
Inorganic Compounds
O Compound Matrix Container Preservative Holding Time
Acidity aqueous 250-mL HDP cool,4 o C 14 days
Alkalinity aqueous 250-mL HDP cool,4 o C 14 days
Ammonia aqueous l-L HDP cool,4 o C, H 28 days
2SO 4 pH<2
Biochemical Oxygen aqueous 2-L HDP cool,4 o C 48 hours
Demand
Bromide aqueous 250-mL HDP none required 28 days
Chemical Oxygen aqueous 125-mL HDP cool,4 o C, H 28 days
Demand 2SO 4 pH<2
Chloride aqueous 125-mL HDP none required 28 days
Chloride solid 4-oz jar none required 28 days
Chlorine, total residual aqueous 500-mL HDP none required analyze immediately
Chromium VI aqueous 250-mL HDP cool,4 o C 24 hours
Chromium VI solid 8-oz jar cool, 4 o C as soon as possible
Color aqueous 125-mL HDP cool,4 o C 48 hours
Cyanide aqueous l-L HDP cool,4 o C 14 days
NaOH pH>12
Cyanide solid 4-oz jar cool,4 o C 14 days
Fluoride aqueous 500-mL HDP none required 28 days
Hardness aqueous 250-mL HDP HNO 3 or H 6 months
2SO 4 pH<z
Hydrogen ion (pH) aqueous 60-mL HDP none required analyze immediately
Hydrogen ion (pH) solid 4-oz jar none required analyze immediately
Kjeldahl and organic aqueous l-L HDP cool,4 o C, H 28 days
nitrogen 2SO 4pH<2
Mercury aqueous 250-mL HDP HNO 3 pH<2 28 days
Mercury solid 8-oz jar none required 28 days
Metals (except Cr VI aqueous 500-mL HDP HNO 3 6 months
and Hg)
pH<2
Metals (except Cr VI solid 8-oz jar 6 months
and Hg)
Nitrate aqueous 250-mL HDP cool,4 o C 48 hours
Nitrate solid 8-oz jar cool,4 o C analyze immediately
Nitrate-Nitrite aqueous 250-mL HDP cool,4 o C, H 28 days
2SO 4 pH<z
Nitrate-Nitrite solid 8-oz jar cool, 4 o C 28 days
Nitrite aqueous 125-mL HDP cool,4 o C 48 hours
Oil and Grease aqueous 2-L wide-mouth cool,4 o C, H 28 daysglass 2SO 4 pH<z
Oil and Grease solid 2-L wide-mouth cool,4 o C 28 days
glass
Compound
Organic Carbon
Organic Carbon
Orthophosphate
Phenolics
Phenolics
Phosphorous
(elemental)
Phosphorous (total)
Residue,
filterable(TDS)
Residue, non- filterable
(rss)
Residue, settleable
Residue, volatile
Silica
Specific conductance
Specific conductance
Sulfate
Sulfate
Sulfide
Sulfide
Surfactants
Turbidity
Contain-er
125-mL HDP
4-ozpr
f ZS-mf HOf
1-L Boston
Round
s-oi jui(Eius.
ontv_)
1-L Boston
Round
125-mL HDP
250-mL HDP
250-mL HDP
250-mL HDP
Imhoff Cone
250-mL HDP
125-mL HDP
250-mL HDP
8-oz jar
125-mL HDP
4-oz jar
l-L HDP
8-oz jar
500-mL HDP
250-mL HDP
Preservative
.ooi,+;c,rrct
orH2SO4
PH'2
c9ol,4 " C
Cool,4 " C
cool,4 o C, H
2So 4 pH:2
cool,4 o C
cool,4 " C
cool,4 o C, H
2SO 4 pH<z
cool,4 o C
cool,4 " C
cool,4 o C
cool,4 o C
cool,4 o C
cool,4 o C
cool,4 o C
cool,4 o C
cool,4 o C
cool, 4 o C
cool,4 o C,
ZnAc + NaOH
pH>9
cool,4 o C
cool,4 o C
cool,4 o C
Holding Time
28 days
28 days
48 hours
28 days
28 days
48 hours
28 days
7 days
7 days
7 days
48 hours
7 days
28 days
28 days
28 days
28 days
28 days
7 days
7 days
48 hours
48 hours
Matrix
aqueous
solid
aqueous
aqueous
solid
aqueous
aqueous
aqueous
aqueous
aqueous
aqueous
aqueous
aqueous
aqueous
solid
aqueous
solid
aqueous
solid
aqueous
aqueous
MEMORANDUM
To: Tom Rushing (DRC), L-oren Morton (DRC), Phil Goble (DRC)
From: Paul Bitter (URS), Jeremy Cox (URS), Michael J. Singleton (SC)
cc: Robert Baird (URS)
Date: 20 March 2011
Re: Comments on Work Plan and Schedule for Supplemental Contaminant Investigation
Report for White Mesa Mill Nitrate Investigation dated Feb. 18, 2011
This memorandum contains the URS and DRC comments on the Work Plan and
Schedule for Supplemental Contaminant Investigation Report for White Mesa
Mill Nitrate Investigation (Work Plan) dated Feb. 18, 201 l, which was prepared
for Denison Mines USA (DUSA) by Intera Corporation. This review has been
performed as a deliverabLe for Contract No. I 16259 issued througlt the Utah
Department of Ent'ironntental QuaLity, Division of Radiation Control (DRC).
This review also is in accordance with the Memorandum of Understanding
(MOU) between the DRC aml DUSA clated February 17, 201 1.lFor purposes of
expediency, the URS and state comments are editedfor conciseness and
combined into one memo for the DRC to copy and submit to DUSA.I-
The review of the Work Plan has been informed by the following documents:
- Summary of work completed, data results, interpretations and recontmendations for the
Juty 2007 Sampling Event at the Denison Mines, USA, White Mesa Uranium Mill Near
'Blanrling, ()tah, preparecl by T. Grant Hurst and D. Kip Solomon of the Department of
Geology and Geophysics at the University of Utah, submitted May 2008.
- Nitrate Contamination lnvestigation Report, White Mesa Uranium Mill Site, Blanding,
Utah,prepared by Intera Corporation, dated December 30, 2009.
- The "Notice of Additional Required Action ktter" (NOTICE) dated October 5, 2010
from DRC to DUSA regarding DRC review of the 2009 report.
- The letter dated November 15, 2010 from DUSA to DRC responding to the NOTICE
listed above.
- A spreadsheet of monitoring well construction data (DUSA WELLCOMP.xIs) and as-
built reports for monitoring wells provided to URS by DRC on February 28,2011.
DRC and URS have reviewed the Work Plan with the support of Michael Singleton, Ph.D., of
Singleton Consulting. Dr. Singleton has approximately 14 years of experience in stable isotope
and geochemical data analysis, including the application of this experience to the assessment of
Page I ofll I'RS
recharge and impacts to groundwater from human and animal waste. Dr. Singleton is the author
or co-author of l7 published papers. His qualifications are available upon request.
The comments regarding the Work Plan are presented below.
In summary, our reviews suggest the following: l) a dynamic conceptual site model should be
produced in the work plan based on current information; 2) the model should be updated during
the investigation to include results of samples analyzed in accordance with the work plan, 3) more
potential sources should be analyzed to test the hypotheses regarding nitrate sources, 4) isotopic
analyses for sulfur and oxygen in sulfate should supplement the proposed isotopic analyses of
nitrate and water to better distinguish potential sources, and 5) the samplin-e be conducted in more
than one phase so the results can be discussed during a conference call with DRC, LIRS, and
Michael Sin-eleton for the purpose of conducting further phase(s) ol investigation with focus and
efficiency.
L General Comment: The 2009 Nihate Contamination Investigation Report (CIR) attempted to
present a conceptual site model (CSM) to explain the presence of elevated levels of nitrate
and chloride in the groundwater beneath the mill. Although it was not refemed to as a "CSM"
in that report, the CSM displays the possible formation of the nitrate/chloride plume in the
center of the propertyl due to one potential source. Since submittal of the ClR, DUSA has
brought forward two other explanations and potential sources of the nitrate and chloride
contamination in meetin-qs with the DRC. Other potential sources (see comment #2 below)
were not fully evaluated in the CSM in the 2009 Nitrate CIR. Ideally, a CSM that comprises
plan and cross section depictions of potential sources should provide the following evaluation
structure, documentation and conclusions regarding potential sources of the plume:
a. Each potential source, described in text and shown on one or more fi-qures; the fi-eure(s)
should be supplemented with site-specific chemical, lithological, hydrogeolo,eical, and
physical data that affect the fate and transport of source material.
b. The physical and chemical means and pathways by which the potential source could be
conveyed to the present location of contamination, described in text and displayed in the
conceptual drawings.
c. Discussion of the analytical and geological data that are available and displayed on one or
more of the figures to support the potential source of the nitrate and chloride
contaminants in groundwater; data that do not support the potential source of the
contaminants also can be displayed to eliminate a potential source.
d. Discussion of the analytical and geological data that are lackin-g (i.e., data gaps) in the
evaluation of the potential source's fate and transport.
e. Description of the data that will be generated during the investigation that will be used to
update the CSM.
The Work Plan should present the CSM with the attributes discussed above, near the
beginning of the document, with all of the successive sections discussed in terms of how the
.-- 'l
i Comment [TRl]: Per the discussion ij during the conference call this issue of II developing a comprehensive plan based
Ii onaconceptualmodelneedstobe iL$T:gr""*U,-*-]
r-"" -""^---'j Comment [TRz]: A definilion of what j
, is considered to be r well developed
It :Sry:g*lj," .qt'h *.!:q !:ry, i
Page2ofll I'R,s
sections contribute to the structure of the CSM. The details of the CSM are discussed in the
followin-s comments.
General Comment; All potential sources for the nitrate and chloride contamination in the
groundwater beneath the mill site must be addressed by the CSM. It is noted and accepted
that one potential source of the nitrate and chloride, the Frog Pond, was dismissed by DRC in
the October 2010 NOTICE and that Denison did not produce any additional evidence for that
potential source in the November 2010 letter responding to the NOTICE. An additional
source, upgradient of the DUSA property, was also dismissed in the 2009 Nitrate
Contamination Investigation Report as being too far from the plume at the center of the
property to possibly be the source of the plume due to the time required for groundwater to
travel from the northern boundary ol the site to the center of the property. The DRC requires
that the CSM identify three (or more if practical) potential sources for the elevated
concentrations of nitrate ancl chloride that were outlined in the 2009 Nitrate CIR and the
November 2010 DUSA memo: namely, (l) naturally-occurring deposits of nitrate and
chloride in the vadose zone mobilized byrecharge from the wildlife ponds or other locations,
such as Lawzy Lake (the "New Theory"), (2) possible soil / groundwater contamination
caused by the US Army missile activities on or near White Mesa. and (3) activities in or
around the mill site, including the leach fields, historical stock watering ponds, and other
potential source areas. The latter would be sub-divided into multiple potential source areas,
as listed in the source review report in the 2009 Nitrate CIR. The three potential sources
could be contributing individually or in cornbination to the current nitrate and chloride
plumes.
Throughout the work plan, figures, maps and cross sections discussed in comment #1, should
be cited as appropriate. The figures must provide the cunent hydrogeologic understanding of
contaminant sources and their fate and transport at the site. ispecifically, DUSA needs to
provide the following regarding the development of maps and cross sections:
a. All potential sources.
b. For cross-sections, the soil types at each depth interval in the subsurface along the path of
the cross-section, based on the available boring logs for at least five wells or sampling
locations.
c. For cross-sections, the depth to groundwater and the direction of groundwater flow; for
maps, the direction of groundwater flow.
d. All relevant analytical data for soil at the locations shown on the maps and cross-sections.
e. All relevant analytical data for groundwater at the locations shown on the maps, with the
current plume boundaries depicted on the cross-section.
f. All relevant site features at the surface along the path of the cross-sections or in the view
of the map.
g. A minimum of two cross-sections should be generated: one rou-ehly north to south, and
one roughly east to west.
4. General Comment: The Work Plan should be structured in such a way that each component
of the Work Plan presents a hypothesis relative to proving or disproving each potential source
Pngelofll
i Comment [TR3]: Per the 3/17ll I
i telephone conferercecall a disussion of
I the needed hlpothesis statement and
i eyidence that the work plan sill conhrm
2.or reject sources/source areas need to be
i included here.I ..
Comment [TR4]: I feel.like this pan
of the section should be deleted since the
CIR has already been eviewed and DRC
requested that the additional sources be
investigrted as was reptrted in Tischlers
Source ReviewReport..
Tom - I don't *e how it hurts to leave it.
Keeping the lilork Plan broad and
comprehensive at this stage of the study
works ro the protection of the
environrneDt. ILMl
Comment [TRs]r This section should
focus on the development of the cross
sections.
Maps tm. lLMl
I'RTi
5.
6.
7.
of nitrate contamination, methods and measurements to test each hypothesis, including the
purpose of sample collections and analysis, and specific criteria to determine whether each
hypothesis has been verified. A "weight of evidence" approach using multiple data to test or
support a hypothesis should be employed whenever possible when evaluatin_q hypotheses.
Section 4.1, third paragraph: Fi-uures 12 through 14, which are referenced in this paragraph,
identify a historical stock watering pond that, upon comparison to Figure 15, is locatecl on the
south end ol the investigation area. approximately half a mile southeast of MW-20 (near
MW-22). The Work Plan should explain the purpose of identifying this pond. Ilthis pond is
illustrated in these figures as part of a response to DRC's discussion of nitrate concentrations
in groundwater downgradient of the site in the October 2010 NOTICE, then such a response
should be presented in the framework of the CSM and in the context of a hypothesis (e.g., a
historical stock watering pond is the source of the elevated nitrate concentrations in MW-20).
Then data that support or refute the hypothesis, and DUSA's conclusion, based on the weight
of evidence, should be identified in the work plan.
Section 4.1, last paragraph and Section 4.2, last paragraph: The assertion of a "strong
potential for military operations on White Mesa that may have led to some or all of the
observed present-day groundwater contamination problems" is a statement that should be
presented as a hypothesis in the work plan and analytical methods should be identified to test
the hypothesis, as discussed above. A calculation of the mass of nitrate in the groundwater
beneath the mill, as discussed in the 2009 Nitrate CIR, demonstrates that a significant mass of
nitrate is present in the saturated zone beneath the mill. It is not clear that launching rockets
from the property is likely to have contributed a significant mass of ammonium or nitrate to
the subsurface. Unlike static rocket motor testing with quenching through water jets, there
would be no mechanism to transport the contaminants to the saturated zone during rocket
launches. Further, the presumed location of the launches is reported to be downgradient of
the current location of the plume. Thele currently is no historical evidence that would
identify the location or nature of support activities associated with the rocket launches. If
DUSA wishes to test the hypothesis that missile operations may have served as source of
nitrate contamination, then the DRC requests that the groundwater at the site be analyzed for
perchlorate. The Pershing rocket motors likely would have contained some amount of
perchlorate that would have been transported to the saturated zone with the other components
of the rocket fuel. The determination as to whether this potential source will be examined
needs to be included in the Work Plan now. If it is to be included, full details regarding the
examination must be provided. If DUSA elects to eliminate past military activities as a
source of nitrate ancl chloricle, this clecision will be considered final by the DRC.
Section 5.0, last paragraph: The 2005 study that is referenced supposedly cites
concentrations with units of milligrams per liter. The text characterizes the concentrations as
concentrations in soil, which should be in units of mass only. The units and results more
likely reflect the leachable concentrations of nitrogen measured during the leachate tests
conducted on the soil samples. Please resolve the discrepancy, and clarify what the
concentrations of nitrate represent in this and other leachate-test discussions in the work plan.
Comment [LM7]: Move this senterce
to lmation << I >>. above-DON E/URS
Prge4ofll I'RS
8.Section 5.1, first paragraph: DRC agrees that some Geoprobe sampling of a naturally-
occurring source of nitrate in the vadose zone is warranted for undisturbed areas during the
investigation, providing that the number of samples is sufficient to characterize a potential
source and its fate and ffansport. The proposerJ number of samples has not been explained or
jusrified in the work plan. DRC requests that DUSA provide a statistical basis for the number
of Geoprobe sample locations in the undisturbed areas in this section of the work plan.
Section 5.2: The expected minimum number of borings must be listed in this section. Table
I indicates that up to four borings are planned. The work plan should be constructed such
that the number and depth of bedrock borings witl be based on the number and results of
Geoprobe sampling locations finally determined necessary to test the nitrogen reservoir
hypothesis, ancl subject to DRC approval prior to corunencement offurther drilling.. .
9.
10. Section 5.2, first paragraph: Background shall be determined by the 957o upper confidence ,,
limit on the mean (95Vo UCL) of all 20 "background" samples collected from soil samples,
and will be subject to DRC approval. Admittedly, some flexibility should be incorporated
into this decision based on the overall results of the Geoprobe investigation. However,
decisions to drill should be made jointly with DRC and should be reflected in the process
flow diagram included in the work plan. The decision to bore further may benefit from a
calculation of the concentration of nitrate in the soil that is expected to result in a
groundwater concentration exceeding the compliance standard for nitrate (i.e., a soil to
groundwater screeni ng level ).
I l. Section 5.2, fourth and fifth paragraphs: DUSA desires to test the hypothesis that naturally- ',
occurring deposits of nitrate and chloride in the unsaturated zone are contributing to the
elevated concentrations of these compounds in the saturated zone beneath the mitl. DRC
recommeads that an additional sample be collected in the unconsolidated interval that
contains the highest concentration of nitrate, as determined by the results of the Geoprobe
investigation, for each drilling location. f!l1e qdcl4rol4l sgqrple shog$,b-e -agqly4e-d fq1 4iq4te
isotopes (nitrogen and oxygen) in addition to the nitrate and chloride analyses via the
synthetic precipitation leachin-e procedure (SPLP) prescribed in the work plan. The
characterization of the nitrate isotopes in these deposits, if present, will assist in determining
whether the nitrate in the groundwater may have originated from the deposits.
12. Section 6. l: Geoprobe sampling around the potential source areas in the mill area is
warranted. However, two of the potential source areas listed with a high priority for
investigation in the source review report (Attachment 2 of the 2009 Nitrate CIR) were not
included in the list of source investigation areas. These two areas are the historical stock
watering pond (near the current location of the sulfuric acid tank) and the northern wildlife
pond. DRC requests that these two areas be added to the list of potential source areas in
Section 6. l, and included in the CSM discussion.
13. Section 6.1: Including the chlorate tanks as a potential source of nitrate may be incorrect.
Based on the information in the source review report, the tanks hold sodium chlorate. lf the
tanks are being investigated as a source ol chloride in groundwater, they should be
characterized as a potential source of chloride. If the tanks have historically held ammonium
Prge5of ll
Comment [PB8]: If we require a
statisticnl lrasis for sample collection,
then lhe sample budget could expand
beyond reasonable expectrtions; what we
usually do is sample in phrses and then
lssess the dila to detemine of more data
are necessary to prove a hypothesis. We
need to resolve this by phone, but I agree
for now to let DUSA detemine the
number of sufhcient samples [Paul Bitter]
Comment [JC11]: Tom, I rnade a
change to your text here. Please verify il
this language is acceptable. In our
investigations, we have typically worked
with a 957o UCL or similar assessment
for background. This value will be
higher than the average, but should help
us focus on the significant sources of
nitrate. lJererny Cox]
Comment [LM12]: True, but rhar is
DUSA's concem. no oun.
Comment [LM13]: Good idea
I'RS
Commerrt [LM9J: Re-word this. The
solution here is to have DUSA beef up
the number of geoprobe borings in the
mill arerl - to be proportionate with the
numtrer of shallow borings outside the
mill area.
Norcetlfor DRC / {JRS to offer to work
up a statistical basis for geoprobe hole
density - let them do that andjustify it in
rheir 2d dftft.
Comment [P10]: Delete - see
previous co[unent for details
chlorate, then this shoLrld be noted with the entry for the chlorate tanks as a potential source
for nitrate. Ifthe tanks have never held ammonium chlorate and are not considered a potential
source for nitrate in the -eroundwater based on operating records, then this potential source
area should be deleted lrom the list ol investigation areas.
14. Figure 2l:The red line for a potential nitrate or chloride source and the red outline for a leach
field scheduled for investigation are indistinguishable. As a result, it is not possible to
determine fromFigure 2l which areas were potential sources that have been determined not
to warant any investigation. DRC requests that the coloring for these two categories of areas
in Figure 2l be revised to make the figure legible.
15. Section 6. 1, fourth and fifth paragraphs: DRC disagrees with the assertion that no subsrtrface
soil samplin-e is necessary at the two active leach fields if the current influent to the leach
fields is sampled. The current content of the influent to the leach fields could be very
different from the influent to the leach fields twenty or thirty years ago. DRC requests that
subsurface soil sampling should occur at these locations and should be supplemented by, not
replaced by, analyses of the influent to the leach field. Performing direct push samplin_q in
several locations within the unconsolidated (shallow) interval in the active leach fields will
not create preferential pathways for waste water to reach the groundwater table, particularly if
the boreholes are sealed with bentonite as stated in the work plan. DRC agrees with the
sampling of the waste water and the use of a mass balance as outlined in this paragraph.
16. Section 6.1, fourth paragraph and Section 6.2 first paragraph: The text in these sections
appears to differ regardin-e which leach fields (SAG leach field or CCD/SX leach field) are
active. Please clarify.
17. Section 6. 1: The minimum number of proposed mill site Geoprobe borings should be listed
in this section. Table I indicates that as many as 13 borings are planned. As discussed
above, the number of mill site borings must be statistically proportionate with the number of
shallow borings drilled in undisturbed areas to determine background nitrate / chloride soil
content. [h{ cgrrent maximqry gf !3 appears to correspond to qqe boring per !44ctive
potential source area. One boring per potential inactive source area is inadequate
characterization of these areas. In addition, the active areas should be sampled (see comment
#15). DRC requests two Geoprobe sample locations for each potential source area that was
rated as a low priority in the source review report (Attachment 2 ol the 2009 Nitrate CIR) and
four Geoprobe sample locations for each of the sources rated as a high priority or those
regarded as likely contributors to the nitrate contamination in the source review report.
However, DRC acknowledges that some of these potential source areas, such as the vaults,
ale relatively small. For the two low-priority vaults, one sampling location will likely be
adequate. This corresponds to one Geoprobe sampling location in each of two sites (sewage
vault/lift station and former vault/lift station), two Geoprobe sampling locations in each of
seven areas (ammonia tanks, Cell I leach field, fly ash pond, chlorate tanks [assuming this
area is retainedl, ammonium sulfate tanks, truck shop leach field, and CCD/SX leach field),
and four Geoprobe sampling locations in each of eight areas (scale house leach field, former
office leach field, northern wildlife pond, Lawzy Lake, Lawzy sump, the historic pond in the
Comment [TR14]: This comment
pere{nail fiom Phil G. My Rationale
for deletion: Intera lisE the Chlorate
Tanks as a Potential Nitrate Source
Location. If DUSA wants to
investigate the tanks as a potential
source, let them. It's not our place
as regulators to limit a
Permitee/Licensee on what they want
to investigate. More information is
never a bad thing"
i fHt anO tom - yes, bur let's leave ir as
I is. lt would be helpful to have DUSA
i disclose the hisrory of the contents for
I rhis trnl. and hr!e rhem substantiatejust
I wllj kind
-9{
soTC: i! :g}ld be. !L-i\4.1 _
j Comment [JC15]l Loren, Tom, and: Phil - The number of Geoprobe borings
I that rve have proposed is not statistically
I bard,just intended to give better
; coverage. Are you suggesting that we
rlter the nurnber of sampling locations so
that the sampling ofeach individu:rl area
is statistically-based, or is the cunent
I nurnber (1, 2, or4) acceptable rs long as
i tlre total number is similar to the number
; of borings in the undisturbed arca?
i [Jeremy CoxJ
Comment [PB16]: We need to
discuss the stat procedures to use during
an investigation. Typicalty, a phased
rpprorch is u rrtional method for testing
hypotheses in incremental steps. Often
you can detemine the outcome of a
hypothesis test well belore completing a
statistically brsed vrmpling regimen.
DUSA may decide that ufter reviewing
the results of only a few samples, that an
extemal nitrate source, not related to mill
operrtions tJoes not exist. Fuflher testing
would be required only to detemine that lrn extemal nitrrte souree did exist. [Paul ]i an extemal nitrate sowe did exist. [Paul ]Binerl i)
Page6ofll I'RS
location of the sulfuric acid tank, the SAG leach field, and the main leach field) for a total of
48 Geoprobe locations at potential source areas in and around the rnill site.
18. Section 6.2, first paragraph: It is unclear whether the procedure for determining whether
nitrate concentrations are "elevated" is the same as that stated in Section 5.2. This section
specifies that the procedures for drilling and sampling are identical to those described in
Section 5.2, but does not explicitly state that the criteria for drilling at a location are the same.
Please clarify.
19. Section 6.2, first paragraph: DRC disagrees with the categorical exclusion of coring in the
active leach fields. This exclusion seems to be based on the theory (presented in Section 6. I )
that the drilling would create preferential pathways for wastewater fluids to reach the
saturated zone. DRC agrees that the deep drilling within the vadose zone underneath active
leach fields could potentially create contaminant transport pathways to groundwater.
However, the creation of pathways may be minimized by the procedures for backfilling the
borings described in Section 5.{ pnC 19qqeq!s tb4t !be-qe9!sio1-ryhe1h91!o driU in the a9t!y9
leach fields (if elevated concenffations of nitrate are discovered in the unconsolidated
material) should be deferred pending further discussion with DRC after analytical data are
available from the Geoprobe sampling and are assessed, rather than pre-emptively ruling out
drilling in these -eas iTh. Work Plan must present the process for evaluatin-e the analytical . -
data from the Geoprobe sampling and determining whether deep coring is required.
Consultation with, and approval of, the DRC regarding the decision to drill and the drilling
locations must be part of the process presented in the work plan. The general planned
locations for coring, if required, must be included in the work plan.
20. $ection 6.2, first p*ugruptJ' In order to test the hypothesls t!r4t elevated concentrations of
nitrate and chloride in the unsaturated zone clue to milling activities are contributing to the
elevated concentrations of these compounds in the saturated zone beneath the mill, DRC
requests that an additional sample be collected in the unconsolidated interval with the highest
concentration of nitrate, as determined by the results of the Geoprobe investigation, for each
drilling location, and that a nitrate isotope analysis (nitrogen and oxygen) be performed on
these samples in addition to the nitrate and chloride analyses via the SPLP. The
characterization of the nitrate isotopes in these locations, if elevated concentrations are
present, will assist in determining whether the nitrate in the groundwater may have originated
from these activities.
21. Section 6.2, first paragraph: DRC agrees that drilling [-f-t-: U-e4ryc4 dlll1ng lqcaliqqs thoql!
be sufficient to characterize the concentrations of nitrate and chloride in the deeper vadose
zone. Although many potential source areas have been identified, DRC anticipates that many
of the potential source areas will not contain elevated concentrations of nitrate and chloride.
Accordingly, the decision of how many bedrock drilling sites selected at the mill site must be
determined after consultation and approval of the DRC.[
22. General comrnent: The work plan must state that all Geoprobe and drilling locations will be
logged by a qualified, Utah Licensed Professional Geologist. Photographs of soil cores are
recommended. The boring logs should be recorded on a form similar to that used for borehole
Gomrrent tfn17l: The work phn I
, needs to definitively accept or refect I
i sources, also, per the Octoben 5,2010 IDRC NOTICE, the plume may be the
result of multiple sources. Therefore let's
go ahead and require them to investigate
flll of the Tischler detemined somes
Comment [TR20]: The work plan
needs to determiae: L The process for
evaluating the shallow cores and making
the determimtioil if deep coring is
required and 2. If deep coring is required
then general planned locations rrced to be
scoped and included in the work plan.
I c;;;;trriiiii i 0",:i,,0*'i,,Jl
. who LIRS is agreeing with. seclion 6.2 I
I does not discuss potenrial creations of
ILpdryg{?:l _ )
comniilt [LM22]r Asain, DUSA
wasts to couch the number of borings as
"up to", w€ need to encomgq them to
say " a minimum of "
Cornrnent [LM23]: Yes - but that is
their wony, not ours. No need to say it.
Comment [LM19]: Tom - in genem],
I am OK with the URS wording, as it
stads. No need to delete it.
Comment ILM21]r Redundant with
the URS request above for Section 5.2 *
bul you can leave it as is.
PageTolll T'RIi
WMMW- l6 that was included in the as-built reports for the wells around the tailings ponds.
The lithological (boring) logs for the installation of the nitrate wells in October 2009 did not
provide all of the necessary information or may not have a location to provide necessary
information, such as sampling intervals, survey data, and other details, and appear to
inconsistently show whether the alluvial materials are consolidated or unconsolidated. This
problem in record keeping is unacceptable. Please revise the field forms to provide a
complete and comprehensive record of field activities and the information required.
23. Section 7: DRC and URS recommend identifying additional locations for isotope analysis in
order to better characterize the source(s) of the nitrate contamination in groundwater. Only
six wells are scheduled to be sampled for stable isotopes of nitrate and water. Only two of
these are within the Mill Site -- too few to assess the nitrate sources in this area. Please revise
the location and number of groundwater isotope samples to be collected on the mill site to
provide statistical power, and be representative of the groundwater quality. There may be
multiple sources and locations contributing to the nitrate plume below the Mill Site. In
addition, only one of the wells (MW-31) scheduled to be sampled for stable isotopes was also
sampled in the Hurst and Solomon (2008) study. Additional wells should be sampled for
stable isotopes that were part of the Solomon study in order to leverage the valuable
groundwater age data from that study in identifying nitrate sources. Well MW-27 is
especially important to include since it is presumed to represent recharge from the Wildlife
Ponds. Well MW-30 should also be included to increase the coverage of high nitrate
groundwater below the Mill Site where groundwater age is known. Well TW4-24 should be
included because it has contained the highest recorded concentrations of nitrate and chloride
in groundwater at the site and is located adjacent to the mill site. Additionally, stable isotope
analysis should be performed atTW4-4, which is located in a separate "lobe" of the nitrate
plume and is also located within the chloroflorm plume. Finally, the influent to the two active
leach fields, like the slimes drain of tailings cell 2, should be sampled to characterize the
isotope signature of any nitrogen compounds used in mill processing activities and released
into wastewater streams. Therefore, DRC and IIRS recommend that MW-27, N/tW-30, TW4-
4,TW4-24, the influent to the main leach field, and the influent to the CCD/SX leach field be
added to the list of locations in Section 7 for stable isotope analyses of nitrate and water.
24. Section 7: In addition to the stable isotope analyses for groundwater, nitrate from samples of
vadose zone soils, from both undisturbed areas and potential source areas within the mill site,
should be analyzed for stable isotope composition as discussed in comments #l I and #20
above: i.e. nitrogen and oxygen isotopes of nitrate found in the soil / rock matrix and/or pore
fluids / groundwater. Such samples are critical for establishing the isotopic signature of
nitrate sources in the vadose zone at this site. Isotope analyses should also be conducted on
l: I distilled water leaches of core samples.
25. Section 7 and Table 2: (a) Two methods that are cunently used to determine oxygen and
nitrogen isotope compositions in dissolved nitrate. The first method (Ion Exchange Method)
uses ion exchange columns to separate nitrate from cations present in the sample, and then
uses chemical treatments to remove sulfate and organic compounds before producing a silver
Comment pC25ll l-oren, Tom,and
Phil - please verify whether URS has
identified the conect active leach field
here. The Work Plan was irronsistent
regarding which leach field, other than
: the main leach field. is active. Ueremy i
; 90*l ,*, )
Comment [JC26]l tcen, we made i
minor modifications to the text you iinsefted here based onMike Singleton's I
i:P,lr-!tfrl-c9*] -- - )
Comment [P824]: For DRC
considemtion. I Paul Bitterl
Page8ofll I'RS
nitrate salt that is then analyzed by combustion/pyrolysis of the salt to produce N2 and CO
gas which is analyzed by isotope ratio mass spectrometry (Silva et al., 2000). The lab
identified in the work plan (lsotech) uses this Ion Exchange Method. A more recent method
(Denitrifier Method) uses a particular strain oi denitrifying bacteria to produce N2O gas
from nitrate in the water sample, which is then analyzed by isotope ratio mass spectrometry
(Sigman et a1.,2001; Caciotti et a1.,2002). The study proposed for DUSA would benefit
from using a lab capable of canying out the Denitrifier Method for two reasons. l) The
Denitrifier Method requires much less sample volumes and lorver concentrations than the Ion
Exchange Method. This will make it possible to analyze the small samples collected frorn
distilled water leached from sediment core samples. 2) The Ion Exchange method can give
erroneous results for oxygen isotope compositions in nitrate if the sulfate is not completely
removed from the sample before producing the silver nitrate salt. If this occurs, both nitrate
and sulfate oxygen contribute to the oxygen isotope composition of the salt produced, thus
incorrectly identifying the nitrate sorrce. Interference from sulfate is a particular concern at
this study site, since sulfate concentrations are much higher than typical groundwaters.
Please resolve this problem in the work plan.
References Cited:
Silva, S.R., Kendall, C., Wilkison, D.H., Ziegler, A.C., Chang, C.C., and Avanzino, R'J,
2000. A new method for collection of nitrate from fresh water and the analysis of
nitrogen and oxygen isotope ratios, J. of Hydrology, 228: 22-36.
Sigman, D.M., Casciotti, K.L., Andreani, M., Barford, C., et al. (2001) A bacterial
method for the nitrogen isotopic analyses of nitrate in seawater and freshwater.Anal.
Chem., 73,4145-4153.
Casciotti, K.L., Sigman, D.M., Hastings, M.G., Bohlke, J.K. et al. (2002) Measurement
of the oxygen isotopic composition of nitrate in seawater and freshwater using the
denitrifi er method, Anal. Chem., 7 4, 4905 - 1226.
(b) Some laboratories that may perform isotopic analyses for nitrate may not be able to
perform isotopic analyses for ammonium. Wastewater samples (see comment #23) may
contain primarily ammonium rather than nitrate. Please deternrine lvhether the majority of
the nitro_een in the wastewater streams is in the form of ammonium or nitrate. If the majority
is present as ammonium, confirm that the laboratory has the ability to perform isotopic
analyses for ammonium, and adjust the work plan to indicate that the wastewater samples will
have isotopic analyses for ammonium rather than nitrate.
26. Section 7: lt is not clear which sources will be differentiated using the isotope compositions
of nitrate. There is a possibility that isotopic signatures of nitrate from ammonium
compounds used in processin_e at the Mill Site may be similar to those of nitrate derived from
septic effluent and treated waste water effluent. Typically, these ammonium sources have
higher delta-l5N values than natural pools of nitrate in the soil zone, but as noted, the ran-ees
for these sources can also overlap in both nitrogen and oxygen isotope composition. It is
likely that stable isotope analyses of nitrate may be useful for testing the hypothesis that
nitrate below the Mill Site is due to mobilization of a natural pool of nitrate in the unsaturated
Proe9ofll uns
soil zone vs. contamination by an ammonium source. trIowever, there are numerous potential
ammonium sources (wastewater effluent, septic effluent, ammonium processing chemicals),
which lead to nitrate with similar isotopic signatures.! It is unlikely that stable isotope
analyses of nitrate will allow for differentiation of the various ammonium sources.
Denitrification can further complicate the use of nitrate isotope compositions for identifying
source compositions by enriching residual nitrate in the isotopically heavier nitro-een and
oxygen. The recharge from the Wildlife Ponds identified by Hurst and Solomon (2008) may
carry organic carbon into the groundwater system where it acts as an electron donor to
support denitrification. Per the study conducted by Hurst and Solomon, it was noted that
sulfate isotopic study is useful to differentiate sulfur sources from the tailings ponds (tailin-es
sulfate) and natural deposits (gypsum). This is because of fiactionation processes occurrin_e
in the ore refining process, and the use of sulfuric acid from an outside source in ore
reflnement. DRC requests that stable isotope analysis of sulfur and oxygen in sulfate be
included with the analysis of every groundwater and wastewater sample analyzed for nitrate
isotopic ratio in Section 7 and Table 2 of the work plan to assist in interpretation and
diffelentiation of the nitrogen ,ou.."s.l !l9qs9 c94!iry4 that tlre cgltlacr laborarory can
perform this analysis. It is unlikely that a sufficient volume of leachate could be produced
from the soil cores (see comment #24) to analyze the isotopic si-snatures of both nitrate and
sulfate in the soil samples. For this reason, DRC is not requestin-q isotopic analysis of sulfur
and oxygen in sulfate in the soil cores. Analysis for sulfate by Method 300.0 should
accompany the sullate isotopic analysis on every -qroundwater and wastewater sample to
provide an additional level of comparison, similar to the 2008 study.
27. Table 2: Usually one sample container can be used fbr oxygen and hydrogen isotopes in
water. One liter is probably more than the analytical lab will need for O and H in water.
Table2 may need to be revised based on input from the analytical lab(s).
28. Section 7.1: lstandard reference materials used by the analytical lab to calculate isotopic
values should be reported. Segtlon 7.1 addresses the need to assess the precision of isotope
measurements, but does not address accuracy. fUse of a second laboratory for analyzing
isotope compositions of a subset of samples would provicle some additional support for the
accuracy of isotope analyses. .] l&"_yS*plqrr_r1e,e!s,1,o,i1cluCe more_narr4tjol qnd a!{it1o14_l
tabled (flow charts) outlining the process for collecting Denison (in-house) QA/QC samples
to self assess laboratory performance (in addition to the laboratory QA/QC protocols). Such
planning needs to include specific sample types [e.g. blind duplicates, field collected spiked
blanks. and field collected spiked matrix (spiked duplicates)l to allow full evaluation of
precision and accuracy. The tables need to include speci{ic wells where the Denison field
QA/QC will be collected as well as specific reference to the matrix used for spike analysis.
The justifications for QA/QC protocols should be included in the nanative (with reflerences
where applicable) and all sample collection (water and soil) should be summarized on
appended tables (see comment 33 below).i
i Comment [TR27]: Need clarification j
i lhat the DLISA contmct hb {lsotech; crn ;
i c9_ldyct the ummo3:* i:g,op: 1nllfi: I
Comment [JC28]: Clrrificrrion :
insened rbove. lJererny Corl
Comment [P29]: Adcl requirernent for
6vS.SOr nnd 6''OSO1 rnrlysis - lsorech.
the lab DUSA will use, according ro their
website can perfom this analysis
I Comment [JC3O]: l-men, URS
accidentally deleted your comnenr here
i regarding the possibility of additional
I aurlyses for ritium, helium, and CFCs.
: URS confered with Mike Singleton over
: the weekend, and he did not recommend
I any additional analyses beyond the
: isotopic analyses for sullate, nitmte, irnd
i water. lJeremy Cox.l
;i Comment [JC31]: lnsened
clarification of contract hb's abiliry to do
:"lli15. i::::r.. P,,9I.: li:'" nlr cot l .
Comment [TR32]: Per discussion
during the 3/17 lelephone convemarion,
there reds to be confirmation that the
contract laboratory can conduct
additional recommended isotopic study,
Sulfate and Oxygen isoropes.
Comment [P33]: Add other QA-QC
samples such as MS/MSD
Comment [1M34]: This is rhe idea
that Phil ws mentiored in yesterday's
confererce cal}. However, if *e can'r get
this kind of QA to work, or if DUSA
refuses to do it for sore reason - ar
altemative would be to have URS collect
split sflmples, and have our own isotopic
analysis done. The expenses for this be
bome by DUSA via another MOA. YoD
will recall. that is similar ro what DUSA
required of us when we had Kip do his
smdy a tew years back. This may be
simpler in the long run. bt's discuss.
Page l0 of I I T'RTi
lS'Urt"L^ (, ^ [r "'t
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* t l'r,r",
{o"nY3."
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29. Section 8: DRC agrees with the conceptual approach of using mass balances as a line of
evidence for potential source areas. However, the comparison of the estimated mass of
nitrate in the groundwater beneath the mill site to the required amount of leachate from the
tailings pond is drawn directly from the 2009 Nitrate CIR. $ince leakage from the tailings
poncls has been ruled out, it would be preferable to compare the mass of nitrate in the
groundwater beneath the mill site to the mass of nitrate that could have been delivered from
naturally-occurring nitrate deposits. ,ln addltiqry a! eltl4qtioJr of the mass of chlorofbrm in
the groundwater beneath the mill site would be helpful for comparing the mass of nitrate or
waste water that could have been delivered to the groundwater tkough leach fields.
30. Figure l: DRC requests that the figure number be inserted into the title. The use of a
decision logic dia-eram is helpful, and could be included in the framework of a CSM. The
current logic diagram (Fi-eure I flow chart) included in the work plan is not sufficient as
clarified in comments above. The work plan is required to contain a comprehensive logic
diagram. Also as stated above, the logic diagram could be included as part of a larger
conceptual model structure, but at minimum this element needs to include specific hypothesis
statements for each activity undertaken for the study in order to definitively accept or reject
identified potential sources. Refer to comments #1,2, and 4 for additional details.
3 l. Figure 3: the legibility of the values and label on the x-axis could be improved.
32. Figure 20: The word "Missile" is misspelled on the legend.
33. Table 2: DRC recommends that the planned sampling be summarized in a table showin-q the
sample locations; number, and types of samples for each location; the types of analyses and
the associated container type, holding time, and preservative; and the planned QA/QC
samples at pre-determined locations. Some of these details are present in Table 2, but
insufficient detail is currently presented in the table. sampling and analysis should conform
to the existing Quality Assurance Plan ior the mill, but the work plan will need to specify the
QA/QC measures for isotopic analysis. Specifically, DUSA needs to clarify the QA/QC
protocols ]whiq! 1v!l! !q qs_e{ lor e4q[ salnple typq 4qd !s_t llqellgposq{ sample logqtiolq 1v!t!r
an identifier. The work plan needs to clarify which samples will conform with the facility
QAP plan, as identified in the section 7. I narrative, and which samples will require additional
QA/QC validation based on inadequacy or inapplicability of the QAP requirements.
Thank you.
URS Corporation
Paul R. Bitter, P.E.
Senior Remediation Engineer
Comment [tM35I: Should we rule ir
out? Remind lre why DUSA ruled it out
Shouldn't samples be uollected frm tie
tuilings wastewalers and N-isotope ratios
detemired? Doesn't this go brck to
working out a comprehensive CSM?
I Comment [JC36]: The 2008 study by
Hurst and Solomon seemed to present
several Iines of evidence supporting a
i lack of leakage from the tailings ponds.j If URS has misundemtood the results
I ftorn that study, additional sarnples could
I be collected fiom the tailings ponds for
I isotopic analysis. Cunently, only the
I "slimes drain" from Cell I is scheduled, for isotopic analysis.
Comment [P37]: Delete - Any
contamination t'om the "fiog pond" has
not been substantiated, see comment #3
above for details
Tom - I agree, we need to re-thinl( this
whole pamgraph, The mass of nitmte that
could have been delivered from the Frog
Pond - will never be known, since no
historic WQ sampling was done there, or
in the groundwater nearby. I LMI
Comment ffR38l: Note that some of
the samples collected for the study will be
required to confom to the existing
Qurlity Assumnce Plar for the mill,
while the isotopic umples will red to
comply with QfuQC measues il
prescribed in the work plm. I think that
these samples need to be clarified up
front and that we probably need 2 Hbles.
Comnrcnt [LM39I: Agai& if we e:rn'r
core l.o agreernent. on how lo go abut
QA/QC, let's rcgotiate collecting our
own sarnples. doing our om isotopic
analysis, and.havi4g DUSA pay for it.
Page ll ofll I'RT;
r==ffi
MEE?A#i*ffifr$
The proposed stable isotope and other analyses for the groundwater, leachate, and tailings
solution samples are as follows:
o nitrate + nitrite
o total Kjeldal nitrogen
o chloride
. 61sNniour" and 618Oriou,"
o 6l8Owater and 6D*r1., (D :2H, Deuterium)
The stable isotope groundwater samples will be collected during the regularly scheduled
quarterly groundwater sampling event conducted by the Site water sampling team.
7.1 Quality Assurance and Quality Control Procedures
The groundwater sampling and analysis procedures are described in the DUSA Quality
Assurance Project Plan (QAP) and on Table 2 of this Work Plan. A commercial laboratory has
been identified that maintains an internal quality assurance program and is able to do all the
stable isotope analyses that are required. Isotech Laboratories, Inc. in Champaign Illinois states
that:
"At least 20% of all analyses at Isotech are for quality assurance and quality control
(QA)C) In addition to regularly calibrating all instruments with standard materials
traceable to the National Institute of Standards and Testing NIST), or the International
Atomic Energy Agency (IAEA), approximately 10% of the analyses are of internal check
standards that have compositions similar to those of the samples being analyzed. For
example, when analyzing methane in samples that are mostly air, we test our methods and
our equipment using standards that are diluted with air, and not with pure gases. An
additional 1A% of all analyses are duplicates of the customer's samples."
Isotech will be required to submit all quality assurance back up data with its final data package
submission. In addition to Isotech's internal quality assurance, the following field-generated QC
samples will be provided: two blind duplicate samples of groundwater, one blind duplicate of
any leachate, and one blind duplicate of slimes drain solution will be sent to Isotech for analysis.
Sufficient amounts of all samples will be collected such that a split sample can be archived
should any reanalysis be required. Any duplicate sample that returns results such that the isotope
ratios differ by more than 20o/o will require reanalysis of all samples. Results of reanalysis will
be statistically analyzed to determine error bars around each data point.
Work Plan for Supplemental Contaminant lnvestigation Report
forWhite Mesa Mill Nitrate lnvestigation 23
\\ralconuata\Pmiec$\luc-001-01-001 Denism Mines\20'1oNifate Response\ll/ork Plan\Work Plan and Sdredule lor Suppplemstd ClR Fhal.dG
February 18,2411
Page I of I
Thomas Rushing ii - Re: Work Plan Review (revised) Briefing for DRC
tt:i$Ma=:-nqr 1r5lrysi:j :::s:l::::
From: <[e-mail]>
To: "Thomas Rushing ii" <[e-mail]>
Date: 3l21l20ll B:29 AM
Subject: Re: Work Plan Review (revised) Briefing for DRC
Yes same number
From: "Thomas Rushing ii' [[e-mail]]
Sentt 0312112011 07:28 AM CST
To: Jeremy Cox
Cc: "Goble, Phillip" <[e-mail]>; [e-mail]; "Morton, Loren" <[e-mail]>; Paul Bitter; Robert Baird
Subject: Re: Work Plan Review (revised) Briefing for DRC
Jeremy,
11 A.M will not work for us. Can we re-arrange the briefing for 9:00 A.M.?
>>> Jeremy CoxiSaltLakeCity/URSCorp 3120120t1 6:33 PM >>>
C;rlerrdar Entry
Call in number: 7- 877 2901337
code: 4190235
If this time does not work for everyone at DRC, please let us know and we
will re-schedule.
fl ha i rJeremy Cox/SaltLakeCity/URSCorp
Invitees
D c.,,,,i ratt [e-mail], Paul
,;il "' " Bitter/SaltLakeCity/U RSCorp@URSCORP,\ru/ [e-mail],[e-mail]
Optlr:nal [e-mail], Robert D(cc) Baird/SaltLakeCity/URSCorp@URSCORP
Plan Review (revised) Briefing for DRC
11:00 AM - 12:00 PM (1 hour)
in number: l- 877 290 1337: code: 4190235
file://C:\Documents and Settings\Trushing\Local Settings\Temp\XPgrpwise\4D870C63EQDOMAINEQRADl00l726271l7... 3l2ll2oll
unsi
MEMORANDUM
Date:
Tom Rushin-q (UDRC)
Paul Biuer (URS),Jeremy Cox (URS), MichaelJ. Singleton (SC)
Robert Baird (URS)
lTMarch 201I
Comments on Work Plan and Schedule for Supplemental Contaminant lnvestigation
Report for White Mesa Mill Nitrate Investigation dated Feb. 18, 201 I
To:
Re:
This memorandum contains the URS comments on the Work Plan and Schedule for Supplemental
Contaminant Investigation Report for White Mesa Mill Nitrate Investigation (Work Plan) dated
Feb. 18,201l, which was prepared for Denison Mines USA (DUSA) by Intera Corporation. This
review has been performed as a deliverable for Contract No. 116259 issued through the Utah
Department of Environmental Quality, Division of Radiation Control (UDRC). This review also
is included in the Memorandum of Understanding (MOU) between the UDRC and DUSA dated
February 17,2011.
The review of the Work Plan by IIRS has been informed by the fbllowing documents:
Summary of work completecl, data resuLts, interpretations and recommendations for the
July 2007 Sampling Event at the Detison Mines, USA, White Mesa Uranium MilL Near
Blanding, Utah, prepared by T. Crant Hurst and D. Kip Solomon of the Department of
Geology and Geophysics at the University of Utah, submitted May 2008.
Nitrate Contamination lnvestigation Report, White Mesa Uranium Mill Site, Blanding,
Utah, prepared by Intera Corporation, dated December 30, 2009.
The dated October 5, 2010
from UDRC to DUSA regarding DRtl li:r,icrv ol'the 2009 report.
TheJgter,dated November 15, 2010 from DUSA to IIDRC responding to the.\QllQ$
listed above.
A spreadsheet of monitoring well construction data (DUSA WELLCOMP.xIs) and as-
built reports for monitoring wells provided to URS by UDRC on February 28,2011.
URS has reviewed the Work Plan with the support of Michael Singleton, Ph.D.. of Singleton
Consulting.-pr. Singleton has approximately 14 years of experience in stable isotope and
geochemical data analysis, including the application of this experience to the assessment of
recharge and impacts to groundwater from human and animal waste. Dr. Singleton is the author
or co-author of 17 published papers. His qualifications are available upon request.
The dralt comments from URS and Dr. Singleton regarding the Work Plan are presented below.
F;"t a **";r"d"* -l
i Deleted:t
i Formatted: Font: 8 ot!l
Page I of l0 ^IInl
In summary, our reviews suggest the following: l) a dynamic conceptual site model should be
produced in the work plan based on current information; 2) the model should be updated during
the investigation to include results of samples analyzed in accordance with the work plan, 3) more
potential sources should be analyzed to test the hypotheses regarding nitrate sources and 4) the
sampling be conducted in more than one phase so the results can be discussed during a
conference call with IIDRC, URS, and Michael Singleton for the purpose of conducting further
phase(s) oI investisation with focus and efficiency.
1. General Comment: The 2009 Nitrate Contamination Investigation {ClR) Report attempted to"
preSen|areaSon4blyye!-deYelqpe4qo1rqeptua!sitemodel(CSM)tgexp!ajn1hq]1es-e4c'eof
elevated levels of nitrate and chloride in the groundwater beneath the mill. Although it was
not referred to as a "CSM" in that report, the CSM displays the formation of the
nitrateichloride plume in the center o[ the property. Since suhrniual ol the CIR. DL SA.has
brouglrt tbr.ward two other expianations and potential soulces of the nitrate and chloride
contamination in rneetines with DRC. ldeally. a*qQryl=il!rgLs!Lil-!t':tl_Ii.ll-dgyg!9!q{:E!1ry ,',
jL=prgyidtllt]rg lillltllliIg gIr!rli4to8=s!!c=t!u.c. !klc=ulr!;?!r!igrl !ul4 ulrnclusiuns ri:gaxling tlt ,'
silurces ol thc Dlunre:
!r,--xx\\
b. XX-.\X,"-cll,
2. Pcr DUSA r:onclLrsions in thc 1009 r'cl;urt il is spcculaterl that $e plume is rlrq;esult of the'
introduction of make-up water, reportedly effluent from the Blanding municipal sewage ,..
treatment plant, into Lawzy Lake and the northemmost wildlife pond throu-eh a pipeline from
"Frog Pond" northeast of the property. althttugtr t
dUebaUe-q_tpetQlc _Lrt1g1,Lre\r rvith tlte (lit.t,assunluiul/&d"-iJr-1hc-Ogebgljl0lg DRC
IlQl,KIl This transfer was reported to have occurred during the time period spanning the
mid-1980s to 1992. As such. the current,Q!\a iq baqed qqgqqgdgtg!gyi{qrycg f1o_r4_rry!_._,
employees, rather than evidence from city oll'icials or treatment plant employees. Further.J:o _ -
historical documentation is available to confirm or deny the presence of elevated
concentrations of nitrate and chloride in the water extracted lrom Frog Pond in that time
period.jowever, the presence of elevatecl concentrations of nitrate and chloride in
groundwater at the northeastern corner of the property indicates that the hypothesis that prog
Pond is a source of nitrare contam.ination in groundwater cannot be rejected based on
available aatal_ttre_CS!1_po1t1qy_e{ jq !lfe_109?Je1lg4_yqs-reinforcecl by the conc_lusiqqs-o_f '
the 2008 report by Hurst and Solomon, which confirmed that recharge from the wildlife
ponds was reaching groundwater, and that the groundwater elevation data across the site
supports the movement of potential contaminants away from ponds to the mill site. .
No discussion ol the CSM cited previously was presented in the Work Plan. The Work Plan
would significantly benefit from reference to and discussion of the CSM at the beginning of
the Work Plan, with all of the following sections discussed in terms of how they inform the
CSM.
i' i;;;;t rrRl r;P;;-dt..,*;
i during the confererce call this issue of
i developing a comprehensive plan based
I on a corceptual model neds to be
i dirussed more fully.
Formatted: Indent: Left: 0",
Numbered + Level: 1 + Numbering
Style: 1, 2, 3, ... r Start at: 1 +
Alignment: Left + Aligned at: 0.25"
; + Tab after: 0" + Indent at: 0.5"
Deleted:
Comment [TR4]: These statements
are ircorect. Pleare refer to the October
5, 2011 DRC Notice of Additional
Required Action and align these
statement specificnlly see the section of
the letter slarting on page 2 and labeled
"lInsubstantiated Nirate Source
Comment [TR7]: Per the 3/17ll I i
i.1e]gqhory.confereme call.a d_iscusfl. Rl-]('" -"----': Formatted: Font:8 Dt
Deleted: ed
Deleted: hat may
Comment [TR2]l A dehnition of what
is considered to be a well developed
conceptual site model is needed here.
Deleted: The CIR site model
Deleted: since
Deleted: d
Comment [LM3]l I agree with Tom.
The DUSA argument is weak. lt is better
lo say the Dt'SA Frog Pond cllim thtt it
is the NO3 source, is unsubstantiated - in
light of tlre comparable N03 levels found
downgradienrwells MW-3, 22, etc.
Comment [P5]: This sratement is
completely untrue, therefore I deleted it
Comment [LM6]: I appeas IIRS may
be right, and this paragraph
Page 2 of l0 ^IIRS
.1. General Comment: URS recommends that the CSM identify four potential sources for the'
elevated concentrations of nitrate and chloride that were outlined in the 2009 Nitrate
Contamination Investigation Report and the November 2010 DUSA memo: namely, (1)
treated sewage effluent introduced at Lavtzy Lake and the northernmost wildlife pond, (2) an
upgradient source originating near Frog Pond, as evidenced by the concentrations of nitrate
and chloride at the northeastern corner of the property. J(3) naturally-occurring deposits of ,'
nitrate and chloride in the vadose zone (the "New Theory"), (4) nossible soil / qroundwater
contamination caused by the US Army missile activities on or near White Mesa. and ($- .'
activities at the mill site, including the leach fields and other potential source areas. The i
latter would be sub-divided into multiple potential source areas. Some of these could include: ,i. 1... L The_ {oq1 &igpglenlial sources qould be contrlbuting individqa.f ly o1!q qqmbila_t!.on ,'
to the current nitrate and chloride plumes.l Maps arlclcross sections must-be presented during
,
the CSM discussion and cited during the discussion of the potential sources aud routes of ',
nitrate transport presented in Section 5 of the Wo.k Plan.-Jllgse figules ,ltustl!r](l,9fg!rql1t_ ',,
_
'Speciiicuillli. L)L ',',,',,,
cross sectlons:
.t. XX,.S[X
b. xxxxx
4. Ceneral Comment: The Work Plan would benefit from a structure in which each componert',' ',',',',
of the Work Plan presents a hypothesis relative to proving or disproving eachDotential ,or... ', ',
,',
of nitrate contamination, measurements to test each ,hypothesis, and specitlc criteria to
determine whether each-hypothesis has been verified.
-5. Section 4.1, third paragraph: Figures 12 through 14, which are referenced in this paragraph, i
identify-a historical stock watering pond that, upon comparison to Figure 15, is located on the i
south end of the investigation area, approximately half a mile southeast of MW-20-lineg ,
MW-22). The Work Plan should explain the purpose of identifying this pond., l, ,(r. Section 4.1, last paragraph and Section 4.2, last paragraph: The assertion of a "strong :'
potential for military operations on white Mesa that may have led to some or all of the il { Numbering stvle: a' b' c' + start
,,, i at: 1 + Alignment: Left + Aligned at:
Formatted: Indent: Left: 0",
Numbered + Level: 1 + Numbering
Style: 1, 2, 3, ... + Start at: 1 +
Alignment: Left + Aligned at: 0.25"
+ r-9! glt€tj 0l: +_ Ildgnl 9!; 0::::
Comment IP8]l Any contamination
from the "ftog pond" has not been
substantiated. See the conections for
Comment #l and do likewise here
Deleted:4
Comment [LMg]: Seemed like there
were a few minor / suldry N03 sources
listed in the CIR. Should we list them
here, or just reference the appmpriate
prges in the CIR? Could also list them in
,r ioohmte.
Comment ffRl0]: I feel like this part
of the section should be deleted since the
CtR hrs alrerdy been reviewed rnd DRC
requested that the additional souces be
inyestigated as was reported in Tischlen
Source Review Report..
Tom - I don't see how it huns to leave it.
Keeping the Work PIan broad and
comprehensive at this stage of the study
works to the protection of the
environrnent. [LMl
Deleted: c
Deleted: should
Deleted: cross sections will
Deleted: needed
Deleted: rhe
Comment [TR11]: This secrion
should focus on the development of the
cross sections.
Maps too. [LM]
Formatted: Numbered + Level: 2 +
Numbering Style: a, b, c. ... + Start
+ Tab after: 0" + Indent at: 0.5"
Deleted: a
Deleted: the
Deleted: the
Deleted:
Comment fTRl2l: This is clarified by
review of the "slug flow behavior'r-141
2:ldd1,,,,,,,..,,,.,-
Formatted: Font: 8 pt
i i I oL. r -ArgrIrrsrrL. Lrrtf Ar9rr< i
observed present-day groundwater contamination problems" is a statement that should be i, I ?/r" + Tab after: 0" + Indent at:
:
. .,. I formatted: Indent: feft: 0", Ihypothesis, see discussion above. A calculation of the mass of nitrate in the groundwater '',',1 | ltumbered + Level: 1 + Numbering i
beneath the mill, as discussed in the 2009 Nitrate Contamination Investigation Report. ',ll ?Y]]:^l^?: l:; ,*^tfljt:l I .. i
observed present-clay groundwater contamination problems" is a statement that should be .,, l?ii*iul i[.ri o;*r"oJ.frti- i
beneath the mill, as discussed in the 2009 Nitrate Contamination Investieation Report, '',' I stvle: t' 2'' 3' "' + start at: 1 +".-D-'-.-" ,,, i Alignment: Left + Aligned at: 0.25,,
demonstrates that a significant mass of nitrate is present in the saturated zone beneath the ', [+1gu9fte! o'+Indentat: 0.5'
mill. It is not clear that launching rockets from the property is likely to have contributed a
significant mass of ammonium or nitrate to the subsurface.pnlike static rocket motor testing
with quenching through water jets, there would be no mechanism to transport the
contaminants to the saturated zone during rocket launches. Further, the presumed location of
the launches is downgradient of the current location of the plume. There currently is no
historical evidence that would identify the location or nature of support activities associated
with the rocket Iaunches. If DUSA wishes to test the hypothesis that missile operations may
P{ge 3 of I0 I]BS
have served as source of nitrate contamination, then URSlggueglLitlrg -eryu4dwate1 qt the site
be analyzed for perchlorate. << I >> '['he*dS&:il-uu{li!"} !H lt \-l],e,qbc,111y:potential lQLrrce
ri'ill hc exarnined lr:qd,s:tg =lr=c=ilqlUdeAiJt.tbe= Yfr}k l]4t !qU" .l{" r=t. i! lil tltl trtclqdgd,J=ull
dr:tails ri:garding thc i:xanrinatiort must be provided.,lIJl!-@
lf1jlgflrE1ffl6 soulct' o['nitlarc and chlorrdc, this decision rvill be considered llnal bv
the DRC. [he Pershing rocket motors likely would have contained some amount of
perchlorate that would have been transported to the saturated zone with the other components
of the rocket fuel, if this hypothesis is correct.]
7. Section 5.0, last paragraph: The 2005 study that is referenced supposedly cites
concentrations with units of milligrams per liter. The text characterizes the concentrations as
concentrations in soil. rvhich should be in units o[ mass units r-rnl]-. The units and results
more likely reflect the leachable concentrations of nitro-een measnred during the leachate tests
conducted on the soil samples. Please lesolve the discrepanc-v. and clarify what the
concentrations of nitrate represent in this and other leachate-test discussions in the work plan.
8. Section 5.1, first para_rraph: URS agrees that some Geoprobe sampling of a naturally-
occurring source of nitrate in the vadose zone is warranted, but the number of borings
proposed for that investigation appears to be disproportionatelv lowl compared to the number
of borings planned lor potential source areas within the mill area. :lt is the opinion of URS
that the hypothesis ol naturally-occurring deposits oi nitrate and chloride in the vadose zone
can be tested with substantially fewer borings in undisturbed areas. ,t URS w-ilf aqqjst
DUSA in determining a statistically-based density of borings necessary to test the hypothesis
that a natural nitrogen reservoir exists at the site, if DUSA desires.
9. Section 5.2: URS agrees that some bedrock drilling locations are wananted. The expected" .
rninimunrlumber of-borings rnust,be listed in this section. Table I indicates that up,o four ...
borings are planned. The work plan should he constructed such that the nurnber and depth ol '
beclrock borines rvill be,hqsgc! oq tle lqryber {n4=Le:{ts=qf Q.oprybg sqlnplilg !oc4t1on .
finally determined necessary to test the nitrogen reservoir hypothesis, and subiect to DRCI
approval. n.
10. Section 5.2, first paragraph: URS agrees with the criterion of nitrate concentrations of "atn
least twice background;, _lrqrrc-$l1;--backgfgUUcl i,fllLl,*"be --clst$!tcd-_1,\jls-_lrgage
c.oncentration ot' all .10--ha-c_kgLo1ud-_iaqdff_ff]"1gS19iU_lqg:.Xll_:_4U&s, 4rt:d:rtill !:e.suLigc:t_
to prior DRC approval., @egbL:SpA9-!q4b_ili1y qhould be incorporqtq4 jqtq tb!_-
decision based on the overall results of the Geoprobe investigation. lkrwever, dec_islgrll_tg_ \
drill should be made jointly with TIDRC and should be reflected in the process flow diagram ',
included in the Work Plan. The decision to bore further may benefit from a calculation of the
concentration of nitrate in the soil that is expected to result in a -eroundwater concentration
exceeding the compliance standard for nitrate (i.e., a soil to groundwater screening level). ,
ll._Section 5.2, fourth and fifth paragraphs: URS understands that DUSA desires to test the '
hypothesis that naturally-occurring deposits of nitrate and chloride in the unsaturated zone are
contributin_g to the elevated concentrations of these compounds in the saturated zone beneatl-r
the mill.--.jURS recommends that an additional sample be collectecl in the unconsolidated
Comment [LM13I: Take allobal
look at this pfuasing. We need to be
blunt and direct with this Licemee.
Instead 0f saying suggests or
recorrmends, we need to say requests,
requires, must, shall. etc. lf URS is
uncomfortable then lets phase it as a
DRC mantlate.
Deleted: suggests
Deleted: rested
Deleted: detemlned up front
Deleted: as a new source then thc work
plan study rrust include
Deleted: this source is not included in
the work plan, then
Deleted: needs to
Comment I-M141: Move this
sentence to lma(ion << I >>, rtrove
Comment [P15]: I disagree. DUSA
is proposing to collect 20 samples. ln
order to achieve nonnality it is
recomended that 30 samples ue
cotlected. The DRC doesn't want DUSA
drawing enoneous conclusions from a
limited number of samples collected.
Remove comment #7
Comment [LM16]3 Re-word tlris.
The solution here is to have DUSA beef
up the nnmber of Beoprobe borings in the
nrill mea - to be proportionate with the
number of shallow borings outside the
mill arex.
tst
Formatted f re-r
Deleted: maxirnum
Deleted: should
Deleted: B
Comment [P17]: Delete - see
previous comme[t for details
Deleted: as recommended by URS,
drilling leuer thrn four borings m( t71
Deleted: the non-geoprobe
Deleted: at each geoprobe lGation, not
I iust from Lhe single non-geoprobe]_ [91
i Deleted: sed on the concentration of
dtrirle in nerrr-surfircc soil srmplf-- J 161
Deleted: S
Deleted: The
Comment [LM18]: True, but rhat is
DUSA's concem. no ours.
Deleted: Unless there is a drilling
objective thal LJRS des not und(tr: 11
! Formatted: Font: 8 Dt\:
Page 4 of l0 I,Rs
interval that contains the highest concentration of nitrate, as determined by the results of the
Geoprobe investigation, for each drilling location. [he a!{!1ion4l sample should be 44alyze!
for nitrate isotopes in addition to the nitrate and chloride analyses via the synthetic
precipitation leaching procedure (SPLP) prescribed in the Work Plan. The characterization of
the nitrate isotopes in these deposits, if present, will assist in determinin-q whether the nitrate
in the groundwater may have originated front the deposits.
ll. Section 6.l: URS agrees that Geoprobe sampling around the potential source areas in the
mill area is warranted. However, two of the potential source areas listed with a high priority
for investi-gation in the source review report (Attachment 2 of the 2009 Nitrate Contamination
Investigation Report) were not included in the list of source investigation areas. These two
areas are the historic stock watering pond (near the current location of the sulfuric acid tank)
and the northern wildlife pond. URS recommends that these two areas be added to the list of
Dotential source areas in Section 6. l. ancl included in the CSM discussion.
13. Section 6.1: Including the chlorate tanks as a potential source ofnitrate may be incorrect.
Based on the information in the source review report, the tanks hold sodium chlorate. If the
tanks are being investigated as a source of chloride in groundwater, they should be
characterized as a potential source of chloride. lf the tanks have historically held ammonium
chlorate, then this should be noted with the entry for the chlorate tanks as a potential source
for nitrate. If the tanks have never held ammonium chlorate and are not considered a potential
source for nitrate in the groundwater based on operating records, then this potential source
area should be deleted lrom the list ol investigation areas.
1.1. Figure2l:Theredlineforapotential nitrateorchloridesourceandtheredoutlineforaleach
field scheduled for investigation are indistinguishable. As a result, it is not possible to
determine from Figure 2l which areas were potential sources that have been determined not
to warrant any investigation. URS recluest\the coloring for these two categories of areas in
Figure 2I be revised to make the tisure lesible.
1"5. Section 6. l, fourth and fifth paragraphs: URS disagrees with the assertion that no subsurface
soil sampling is necessary at the two active leach fields if the current influent to the leach
fields is sampled. The curent content of the influent to the leach fields could be very
different from the influent to the leach fields twenty or thirty years ago. URS requestEthat
subsurface soil sampling should occur at these locations and should be supplemented by, not
replaced by, analyses of the influent to the leach field. Performing direct push sampling in
several locations within the unconsolidated (shallow) interval in the active leach fields will
not create preferential pathways for waste water to reach the groundwater table, particularly if
the boreholes are sealed with bentonite as stated in the Work Plan. IIRS agrees with the
sampling of the waste water and the use of a mass balance as outlined in this paragraph.
!6-Section 6.1, fourth paragraph and Section 6.2 first paragraph: The text in these sections
appears to differ regarding which leach fields (SAG leach field or CCD/SX leach field) are
active. Please clarify.
!_._Section 6. l: The minimum number ol'proposed nrill site Geoprobe borings should be listed
in this section. Table I indicates that as nlany as l3 borings are planned. As discussed
Comment [LM19]: Good idea.
i.formattea; Fonti 8 pt I_)
Phil and Tom - yes, but let's leave it as
is. It would be helpful to have DUSA
disclose the history of the contents for
this tlnk. rnd have thern substantiate just
what kind of source it could be. [LMl
Page 5 of l0 I|eE
above. the nunrber ol nrill site borines must be statisticallv Drt)Dortionate rvith the number of
shallorv borinqs drilled in undisturbed areas to determine backqround nitlate / chloride soil
content. This value appears to correspond to one boring per inactive potential source area.
One boring per potential inactive source area is inadequate characterization of these areas.
URS requests,two Ceoprobe sample locations for each potential source area that was rated as
a low priority in the source review report (Attachrnent 2 of the 2009 Nitrate Contamination
Investigation Report) and four Geoprobe sample locations for each of the sources rated as a
high priority in the source review report. However, IIRS acknowledges that some of these
potential source areas, such as the vaults, are relatively small. For the two low-priority
vaults, one sampling location will likely be adequate._This corresponds to one Geoprobe
sampling location in each of two sites (sewage vault/lift station and former vault/lift station),
two Geoprobe sampling locations in each of nine areas (scale house leach field, former office
leach field, ammonia tanks, Cell I leach field, fly ash pond, chlorate tanks [assuming this area
is retainedl, ammonium sulfate tanks, truck shop leach field, and CCD/SX leach field), and
four Geoprobe samplin-e locations in each of six areas (northem wildlife pond, Lawzy Lake,
Lawzy sump, the historic pond in the location of the sulfuric acid tank, the SAG leach field,
and the main leach field) for a total of 44 Geoprobe locations at potential source areas in and
around the mill site. , !
lli. _Section 6.2, first paragraph: lt is unclear whether the procedure for determining whether
nitrate concentrations are "elevated" is the same as that stated in Section 5.2. This section
specifies that the procedures for drilling and sampling are identical to those described in
Section 5.2, but does not explicitly state that the criteria for drilling at a location are the same.
Please clarify.
l,!.,.section 6.2, first paragraph: URS agrees that the deep clrilling within the vadose zone
underneath active leach fields could potentially create contaminant transport pathways to
groundwater. However, the creation of pathways may be minimized by the procedures for
backfilling the borings described in Sect.ion 5.2. ; !
l-Q-gection 6.2, first paragrap!, _ !n_ qr.$91 tcr tgst tbe lypot[ejlg tlrqt elevaqed coqgenlrqliqns,oJ
nitrate and chloride in the unsaturated zone due to milling activities are contributing to the ,
elevated concentrations of these compounds in the saturated zone beneath the mill, URS
requestsJh4t an qddltlon4l sa4ple be collqctq{t1 tlq gqco4solid4t_ed lqtqry4l ry!1[tJre highest
,
concentration of nitrate, as determined by the results of the Geoprobe investi-qation, for each
drilling location, and that a nitrate isotope analysis be performed on these samples in addition
to the nitrate and chloride analyses via the SPLP. The characterization ol the nitrate isotopes
in these locations, if elevated concentrations are present, will assist in determining whether
the nitrate in the groundwater may have originated from these activities.
l,l.,.Section 6.2, first paragraph: URS a-qrees that tlriltinepf l3 bedrock drilling locations should
.
be sufficient to characterize the concentrations of nitrate and chloride in the deeper vadose
zone. Although many potential source areas have been identified, URS anticipates that many
of the potential source areas will not contain elevated concentrations of nitrate and chloride.
Deleted: recommends
Deleted: If this total is not achievable
with the budget cunently available. theD
priority should be given to the sources
rated as l high priority in the source
review report
Deleted:
Comment [TR22]r I don't understand
who URS is agreeing with, section 6.2
does not discuss potential creations of
pathwilys?'l??
Comment [TR24]: The work plan
needs to determine: L The process for
I evulurting rhe shallow cores and making
I the detemitration if drep coring is
result of multiple sources. Therefore let's
go ahead and require them to investigate
all of the Tischler determined sources
Tom-IageelLM]
I required und 2. lfdeep coring is required
I then generrl pl;rmed locations reed to be
I scoped rnd included in the work plun.
\,=.,,,,.,,,,..,,,.,=,,,- -.
Deleted: URS recommends
Deleted: thnt the decision whether to
driU in the active leach fields (if elevated
concentrations of nitrate are discovered in
the unconsolidated material) should be
defened pending further discussion with
UDRC after analytical data are available
from the Geoprobe sampling and are
i assessed, nther than pre€mptiyely ruling
i out drilling in these areas.
i Comment [TR21II The work plan'l needs to definitively accept or refect
, I sources, also, per the Octobem 5,2010
I DRC NOTICE, the plume mry be the
Commeht [LM23l: Tom - in general,
I am OK with the URS wording, as ir
stands. No need to delete it.
Comment [LM25]: Redundant with
the tlRS request above for Section 5.2 -
but you can leave it as is.
Deleted: recommends
Comment [LM26I: Again, DUSA
wants to couch the number of borings as
"up to", we need to encourage them to
say " a minimum of "
Deleted: the curent maximunr
Formatted: Font:
Page 6 of 10 .I'B$
Accordinqlv. tlre decision of how manv bedrock drilling sites selected at the mill site ntust be
cleterrnined atter consultation and approval of the DRCJ
12. General comment: The Work Plan should state that all Geoprobe and drilling locations will
be logged by a qualified and Litah Licensed Pr<-rl'essionalS-eglo-erst Phgloglaplq g{so1l coles
are recommended. The boring lo-es should be recorded on a form similar to that used for '.
borehole WMMW-16 that was included in the as-built reports for the wells around the
tailings ponds. The lithological (boring) logs for the installation of the nitrate wells in
October 2009, which were provided to URS with the as-built report, did not fill in all of the
necessary information or may not have a location to provide necessary information, such as
the sampling intervals, survey data, and other details, and appear to inconsistently show
whether the alluvial materials are consolidated or unconsolidated. This problern in record
keening will not be toleratecl. Please revise the field forrns to prrrvide a complete and
ctrnrpreherrsive recorcl ol lieltl aclivities arrd llte infortttation requiret.l,
?3-section 7: URS recommends identifying additional locations for jsolo1e an4lysiq in qr(g1to - -
better characterize the source(s) of the nitrate contamination in groundwater. Only six wells
are scheduled to be sampled for stable isotopes of nitrate and water. Only two of these are
within the Mill Site -- too few to assess the nitrate sources in this area. Please revise the
location and number ol groundwater isotopic sanrples to be collectecl on the mill site to
rrlovide statistical porver. and be representative. There may be multiple sources and locations
contributing to the nitrate plume below the Mill Site. In addition, only one of the wells (MW-
3l) scheduled to be sampled for stable isotopes was also sampled in the Hurst and Solomon
(2008) study. Additional wells should be sampled for stable isotopes that were part of the
Solomon study in order to leverage the valuable groundwater age data from that study in
identifying nitrate sources. Well MW-27 is especially important to include since it is
presumed to represent recharge from the Wildlife Ponds. Well MW-30 should also be
included to increase the coverage of high nitrate groundwater below the Mill Site where
groundwater age is known. Additionally, stable isotope analysis should be performed at
TW4-4, which is located in a separate "lobe" of the nitrate plume and is also located within
the chloroform plume. Finally, the influent to the two active leach fields, like the slimes
drain of tailings cell 2, should be sampled to characterize the isotope signature of any
nitrogen compounds used in mill processing activities and released into wastewater streams.
Therefore, URS recomrnends that MW-27, MW-30, TW4-4, the influent to the main leach
field, and the influent to the CCD/SX leach field be added to the list of locations in Section
Tfor stable isotope analyses.
l-{-Section 7: In addition to the stable isotope analyses for groundwater, nitrate from samples off
vadose zone soils,_from both undisturbed areas and potential source areas within the mill site,
shoulcl be analyzed for stable isotope composition as discusse<I in comments +itO anO #14
above; i.e. nitroeen isotopes found in nitrate / nitrite firund in the soil / rock matrix an(Vor
pore fluicls / groundwater)._Such samples are critical for establishing the isotopic signature of
nitrate sotrces in the vadose zone at this site._lsotope analyses should also be conducted on
I : I distilled water leaches of core samples.,
gRE
Comment [LM27]: Yes - but thxr is
thatr -""r. ,"t "r*
Deleted: As previously st:rted, given
the relatively high cost ofdrilling
multiple boreholes into the consolidated
fonnation, drilling should be avoided if
pos5iblc lo fmus efforts on identifying
source arers rather than collecting
:"ryq!g,dgjj",I
Deleted: g
Deleted:
Deleted: nitrate
Formattedi Indent: Left: 0",
Numbered + Level: 1 + Numbering
Style: 1, 2, 3, ... + Staft at: 1 +
Alignment: Left + Aligned at: 0.25"
+ Tab after: 0" + Indent at: 0.5"
Comrnent [LM28l: Update reference
numbers.
Page 7 of l0
l-5. Section 7 and Table 2: Two methods that are currently used to determine oxygen and"
nitrogen isotope compositions in dissolved nitrate. The first method (lon Exchange Method)
uses ion exchange columns to separate nitrate from cations present in the sample, and then
uses chemical treatments to remove sulfate and organic compounds before producing a silver
nitrate salt that is then analyzed by combustion/pyrolysis of the salt to produce N2 and CO
gas which is analyzed by isotope ratio mass spectrometry (Silva et al., 2000). The lab
identified in the work plan (Isotech) uses this Ion Exchange Method. A more recent method
(Denitrifier Method) uses a particular strain of denitrifying bacteria to produce N2O gas
from nitrate in the water sample, which is then analyzed by isotope ratio mass spectrometry
(Sigman et al.,2001; Caciotti eta1.,2002). The study proposed for DUSA would benefit
flom using a lab capable of carrying out the Denitrifier Method for two reasons. l) The
Denitrifier Method requires much less sample volumes and lower concentrations than the Ion
Exchange Method. This will make it possible to analyze the small samples collected from
distilled water leaches from sediment core samples. 2) The lon Exchan_ae method can -eive
erroneous results for oxygen isotope compositions in nitrate if the sulfate is not completely
removed from the sample before producing the silver nitrate salt. If this occurs, both nitrate
and sulfate oxygen contribute to the oxygen isotope composition of the salt produced, thus
incorrectly identifying the nitrate source. Interference from sulfate is a particular concern at
this study site, since sulfate concentrations are much higher than typical groundwaters. Please
resolve this problern in the workplan.
References Cited:
Silva, S.R., Kendall, C., Wilkison, D.H., Ziegler, A.C., Chang, C.C., and Avanzino, R.J,
2000. A new method for collection ol nitrate from fresh water and the analvsis of
nitrogen and oxygen isotope ratios, J. of Hydrolo-qy, 228:22-36.
Sigman, D.M., Casciotti, K.L., Andreani, M., Barford, C., et al. (2001) A bacterial
method for the nitrogen isotopic analyses of nitrate in seawater and freshwater.Anal.
Chem., 13,4145-4153.
Casciotti, K.L., Sigman, D.M., Hastings, M.G., Bohlke, J.K. et al. (2002) Measurement of the"
oxygen isotopic composition of nitrate in seawater and freshwater using the denitrifier method,
Anal. Chem., 74,4905-l)?6. Section 7: It is not clear which sources will be differentiated
using the isotope compositions of nitrate. There is a possibility that isotopic signatures of nitrate
lrom ammonium compounds used in processing at the Mill Site mav,be sjmilar tg thosq S!!i!rqte_ - -
derived from septic effluent and treated waste water effluent. Typically these ammonium sources
have higher delta-l5N values than natural pools of nitrate in the soil zone, but as noted, the
ranges for these sources can also overlap in both nitrogen and oxygen isotope composition. It is
likely that stable isotope analyses of nitrate may be useful for testing the hypothesis that nitrate
below the Mill Site is due to mobilization of a natural pool of nitrate in the unsaturated soil zone
vs. contamination by an ammonium source. However, there are numerous potential ammonium
sources (wastewater effluent, septic effluent, ammonium processing chemicals), which lead to
nitrate with similar isotopic signatures. lt is unlikely that stable isotope analyses of nitrate will .
allow for differentiation of the various ammonium sources. Denitrification can further complicate
F#;til;i";""t,t;ft, 0i; - ".i
Numbered + Level:1+ Numbering i
Style: f, 2, 3, ... + Start at: I + :
Alignment: Left + Aligned at: 0.25" j
+ Tab after: 0" + Indent at: 0:51_ _j
Deleted: will likely
ft".*.t t nnZ* N".d.t*r;i", II that the DUSA contmt lab (kotech) cm r
I conduct the amoaium isotope malysis tL-
i Fglnaltedi lont:8 p!
_
Page 8 of l0 ^uR$
the use of nitrate isotope compositions tbr identifying source compositions by enriching residual
nitrate in the isotopically heavier nitrogen and oxy,een. The recharge from the Wildlife Ponds
identified .
by Hurst and Solomon (2008) may carry organic carbon into the groundwater system where it
acts as an electron donor to support denitrilication.- I'er the-.-!U-d:,1:t).Lth!gi!d bll-[g;1anrt
tuilingq pontl_r {ltilirtqs suLla$l-3txl |}!l"!gl.i!l-tlq}eillig:tUUtllt**tltS-]l-!]9!.lull ollf4tll)11!{"1!t!l
procLrssrrs t.reuunirtg irt thc ote tclirling Itt-(fioss.ttnd th
',, ,t* Luttu,],,r*fn.. t,rr.,utt in .=utfg,r-=.orlpuu,lO, t,.
includctl in thc u,rirk plur to assist in inter?retation and differentiation of the nitrosen sources. ,
27. Table 2: Usually one sample container can be used for oxygen and hydrogen isotopes in*
water. One liter is probably more than the analytical lab will need for O and H in water.
Table 2 may need to be revised based on input from the analytical lab(s),
l$ Section 7.1: Standard reference materials used by the analyical lab to calculate isotopic*
values should be reported. Section 7.1 addresses the need to assess tlre pleciqion of isotope
measurements, but does not address accuracy. Use of a second laboratory for analyzing
isotope compositions of a subset of samples would provide some additional support_for the
accuracy of isotope analyses .l il'he r,,,,x"k *[tn neetls {o ilclurte rrrore nara{ion and additiohal
tirhled (llow clriurs) r'rutlinins the $rruelr {i:r collectint Denison (in-ltouse) OAIQC santpJe to
sclf assr-ss labolattx'-v irerl'urniarlc-q {in jrrlqlitior} to thr: laborator-r' OA/OC=protocols). Sur:lr
planning nceds to include spr:cilic sarnpl.c tyf)cs Ir:.g. blind duplicates. lielcl collecled spiked
blanks, anti l'iekl cullccted sprkcrl mttrix (spiked duplicates)l (o tllorv I'ull evaluation ol'
pacision and accur c!_,.1qinclude specillc wells where the Dcnison i'iekj
QA/OC rvill be collecLed al well as ipeqtliq telqrqnce to the nratrix Lrsed fbr spike;rnalysil.
The -iustificatiorrs rirr OAIOC pt'otocols slrpulcl.he i.ncluded jnlhe narratiys: (rvith ret'erences
u'lrcrc alrpliclrhlc) antl ull slnrlrlc clrll.'.'tiorr (rtatct' attrl stlil) shoultl be summarizcd on
anpendeil tables (see con]ment J3 bq&,llvir[gSection 8: URS agrees with the conceptual ,'
approach of using mass balances as a line of evidence lor potential source areas. However,
the comparison of the estimated mass of nitrate in the groundwater beneath the mill site to the
required amount of leachate from the tailings pond is drawn directly from the 2009 Nitrate
Contamination lnvestigation Report. Since leakage from the tailings ponds has been ruled
out, 4 ryoulc! !e prg{elqble to compa{e {e ryr4ss of 4!t!aJe rn t! e- gtogq{ryqte-r-bggeatb Lh-e llill ,'
site to the mass of nitrate that could have been delivered from Frog Pond. . i.Ur In 3qqi!iS!,
an estimation of the mass of chloroform in the groundwater beneath the mill site would be
helpful for comparing the mass of nitrate or waste water that could have been delivered to the
groundwater through leach fields.
]QFigure l: URS suggest that the figure number be inserted into the title. The use of a decision"
losic diasram is heloful. and could be included in the framework of a CSM. -fhc curre nt losit:
,lilgjLtr_t_1_[_UUS_L]h.UrjfUU-U:eLUilgiJ" ir1_llfC'-]g* plarr is-11999[,!c.ig11li1s clrtriflccl irr cotrttrcnts
abtlyg. 'l'hc Work Plan.is rctttrircd._1o*{"!.r,rtjr!l i! 9tI-lU]ICi_U!t11-\-. logic diltrl'tlM
abor.c. the kr!ic diagrarn could lre inrludr:{a.r3ri{ ol u larqcr conecptual nurtlel structure. ltttt at
Hanging: 0.25", No bullets or
numbering
Comment [TR32]: Per discussion
during lhe 3/17 telephone conversation.
there needs to be confirmation that the
contract laboratory can conduct
additional rccommended isotopic study,
Sulfate and Oxygen isotopes.
Deleted: .ll
Comment [P35]: oetete - .+ny
contamination from the "fiog pond" hJs
not been substantiated- se coment #3
above for details
Tom - I lgree, we need to re{hink this
whole paragraph. The mass of nitrate that
could have been delivered from the Fmg
Pond - will rever be known. sirrce no
historic WQ sampling was done there, or
in the groundwater nearby. [LM]
Formatted: No bullets or
numbering
I
Il
Comment [P3O]: Add requirement for
5IS-S04 and 6r8OSOa analysis - lsotech,
the lflb DUSA will use, according to their
website can perfomr this analysis
Comment [LM3,.I: whar about
rritium, and tritogenic helium? Will
CFCS be helptul? Kip included them,
why shouldn't we? We may only get I
chance to do this srudy - to try to unravel
the source(s) of the N conttrmination.
Deleted:11
Comment [P33]r Add other QA-QC
samples such as MS/LISD
Comment [LM34J: This is fie idea
that Phil was mentioned in yesterday's
confereme call. However, if we can't get
thi$ kind of QA to work, or if DUSA
rcftrses to do it for some rcason - an
ilternative would be to have URS collect
split silrnples, and lLlve our own isotopic
analysis done, The expenses for this be
bome by DUSA via anotherMOA. You
will recalll thar is similar to what DUSA
rcquired of us when we had Kip do his
study a few ysurs back. This may be
simpler in the long run. kt's discuss.
Comment [Lit3SI: Should we rule it
out? Remind me why DUSA ruled it out.
Shouldn't samples b9 collected fiom the
tailings wastewaters and N-isotope ratios
detennined? Doesn't this go back to
wofking dut 4 cofiipreheflsive CSM?
Prge 9 of l0 ^I'RS
ntinitturnt this elc't'nent nee:ds to inclricle spc:ciljc hWothesis statenrents hrr each actil itv
undortakc-n firr tlre stucl:y ingdq1tl jgn$$-clv ae'gs14or re-i-Cllglgrllfllgdglq]ltjtbources. Thq
loqi q$irgtaJt gqc4: Lttigqttr] y llU=tqUqyi! g IAB!rgte!s;_&
rt
3lFigure 3: the legibility ofthe values and label on the x-axis could be improved.
llFigure 20: The word "Missile" is misspelled on the legend.
-l3Table 2: URS recommends that the planned sampling be summarized in a table showing the
sample locations; number, and types of samples for each location; the types of analyses and the
associated container type, holding time, and preservative; and the planned QA/QC samples at pre-
determined locations. Some of these details are present in Table 2, but insufficient detail is
currently presented in the table. Snecil'icallv. Dt rSA rreeds to clarilr the bAIQC protocols ju hich
rvill l;e useri fbr each sanrple tr-pe___igg!_list$re p{qprised sanlple locations rvith an identif ier. 'Ihg
rvork plaii needs to clarif.y which samples rvill confirlm u,itli the lacilitv OAP plan. as identif ictl
in the section 7.1 narrative. and rvhich s;unples rvill ri:qqile-iLlclili12l]ill OAIQC validiatiou ha^sed
on inadettuacv or inarrplicabilitv ol'fhe QAP reqrrirenrents.
If you have any questions regarding these comments, please contact me at 801-904-4043 or at
rraul [e-mail]. Thank you.
URS Corporation
Paul R. Bitter, P'E.
Senior Remediation Engineer
Deleted: g
ComHGnt [LM37l: Anorher option,
would be. to rdfer.the r€ader to the bullet
list in the. sdotion above, on what a CSM
needs t0 have.
Coihrnent pR38l: Nore thar sorrn of
the sarples collected fm the study will be
required to coriforin to iheexisting
Quality Assuance Plan for the mill,
while the isotopic smples will need to
comply with QA/QC mesures as
prescribed in tle work plan. I think that
these sarnples reed to be clarified up
frort and that we need 2 tables.
Comment [LM39]r AgairL if we can't
come to sgreermnt on how to go about
QR"/QC, let's negoriate collecting ow
own samples. doing our own isotopic
analysis, ond having DUSA pay for it.
Prge l0 of l0 pltS
MEMORANDUM
To:
From:
cc:
Date:
Re:
Tom Rushing (UDRC)
Paul Bitter (URS), Jeremy Cox (URS), Michael J. Singleton (SC)
Robert Baird (URS)
l7 March 2011
Comments on Work Plan and Schedule for Supplemental Contaminant Investigation
Report for White Mesa Mill Nitrate Investigation dated Feb. 18,2017
This memorandum contains the URS comments on the Work Plan and Schedule for Supplemental
Contaminant Investigation Report for White Mesa Mill Nitrate Investigation (Work Plan) dated
Feb. 18, 2011, which was prepared for Denison Mines USA (DUSA) by Intera Corporation. This
review has been performed as a deliverable for Contract No. 116259 issued through the Utah
Department of Environmental Quality, Division of Radiation Control (UDRC). This review also
is included in the Memorandum of Understanding (MOU) between the UDRC and DUSA dated
February 17,2011.
The review of the Work Plan by URS has been informed by the following documents:
- Summary of work completed, data results, interpretations and recommendations for the
July 2007 Sampling Event at the Denison Mines, USA, IYhite Mesa Uranium Mill Near
Blanding, Utah, prepared by T. Grant Hurst and D. Kip Solomon of the Department of
Geology and Geophysics at the University of Utah, submitted May 2008.
- Nitrctte Contamination Investigation Report, White Mesa Urqnium Mill Site, Blanding,
Utah,prepared by Intera Corporation, dated December 30,2009.
- The memorandum dated October 5, 2010 from UDRC to DUSA regarding the 2009
report.
- The memorandum dated November 15, 2010 from DUSA to UDRC responding to the
memo listed above.
- A spreadsheet of monitoring well construction data (DUSA WELLCOMP.xIs) and as-
built reports for monitoring wells provided to URS by UDRC on February 28,2011.
URS has reviewed the Work Plan with the support of Michael Singleton, Ph.D., of Singleton
Consulting. Dr. Singleton has approximately 14 years of experience in stable isotope and
geochemical data analysis, including the application of this experience to the assessment of
recharge and impacts to groundwater from human and animal waste. Dr. Singleton is the author
or co-author of l7 published papers. His qualifications are available upon request.
The draft comments from URS and Dr. Singleton regarding the Work Plan are presented below.
Page I of9 uns
'rt
In summary, our reviews suggest the following: l) a dynamic conceptual site model should be
produced in the work plan based on current information; 2) the model should be updated during
the investigation to include results of samples analyzed in accordance with the work plan, 3) more
potential sources should be analyzed to test the hypotheses regarding nitrate sources and 4) the
sampling be conducted in more than one phase so the results can be discussed during a
conference call with UDRC, URS, and Michael Singleton for the purpose of conducting further
phase(s) of investigation with focus and efficiency.
l. General Comment: The 2009 Nitrate Contamination Investigation Report presented a
reasonably well-developed conceptual site model (CSM) that may explain the presence of
elevated levels of nitrate and chloride in the groundwater beneath the mill. Although it was
not referred to as a "CSM" in that report, the CSM displays the formation of the
nitrate/chloride plume in the center of the property. The plume is reported to be a result of
the introduction of make-up water, reportedly effluent from the Blanding municipal sewage
treatment plant, into Lawry Lake and the northemmost wildlife pond through a pipeline from
"Frog Pond" northeast of the property. This transfer was reported to have occurred during
the time period spanning the mid-1980s to 1992. The CSM is based on anecdotal evidence
from mill employees, rather than evidence from treatment plant employees, and no historical
documentation is available to confirm or deny the presence of elevated concentrations of
nitrate and chloride in the water extracted from Frog Pond in that time period. However, the
presence ofelevated concentrations ofnitrate and chloride in groundwater at the northeastem
corner of the property indicates that the hypothesis that Frog Pond is a source of nitrate
contamination in groundwater cannot be rejected based on available data. The CSM
portrayed in the 2009 report was reinforced by the conclusions of the 2008 report by Hurst
and Solomon, which confirmed that recharge from the wildlife ponds was reaching
groundwater, and that the groundwater elevation data across the site supports the movement
of potential contaminants away from ponds to the mill site.
No discussion of the CSM cited previously was presented in the Work Plan. The Work Plan
would significantly benefit from reference to and discussion of the CSM at the beginning of
the Work Plan, with all of the following sections discussed in terms of how they inform the
CSM.
s.rD-D
ltfra
(tu'tl
2. General Comment: URS recommends that the CSM identify four potential sources for the Q4lr'""
elevated concentrations of nitrate and chloride that were outlined in the 2009 Nitrate
Contamination Investigation Report and the November 2010 DUSA memo: namely, (l) -
treated sewage effluent introduced at Lawzy Lake and the northernmost wildlife pond, (2) an
upgradient source originating near Frog Pond, as evidenced by the concentrations of nitrate
and chloride at the northeastern corner of the property, (3) naturally-occurring deposits of
nitrate and chloride in the vadose zone (the "New Theory"), and (4) activities at the mill site,
including the leach fields and other potential source areas. The latter would be sub-divided
into multiple potential source areas. The four potential sources could be contributing
individually or in combination to the current nitrate and chloride plumes. Cross sections
Page 2 of 9 I'NB
J.
4.
5.
should be presented during the CSM discussion and cited during the discussion of the
potential routes of nitrate transport presented in Section 5 of the Work Plan.
General Comment: The Work Plan would benefit from a structure in which each component
of the Work Plan presents a hypothesis relative to proving or disproving a source of nitrate
contamination, measurements to test the hypothesis, and criteria to determine whether the
hypothesis has been verified.
Section 4.1, third paragraph: Figures 12 through 14, which are referenced in this paragraph,
identiff a historical stock watering pond that, upon comparison to Figure 15, is located on the
south end of the investigation area, approximately half a mile southeast of MW-20. The
Work Plan should explain the purpose of identiffing this pond.
Section 4.1, last paragraph and Section 4.2, last paragraph: The assertion of a "strong
potential for military operations on White Mesa that may have led to some or all of the
observed present-day groundwater contamination problems" is a statement that should be
presented as a hypothesis in the work plan and analytical methods prescribed to test the
hypothesis. A calculation of the mass of nitrate in the groundwater beneath the mill, as
discussed in the 2009 Nitrate Contamination Investigation Report, demonstrates that a
significant mass of nitrate is present in the saturated zone beneath the mill. It is not clear that
launching rockets from the properly is likely to have contributed a significant mass of
ammonium or nitrate to the subsurface. Unlike static rocket motor testing with quenching
through water jets, there would be no mechanism to transport the contaminants to the
saturated zone during rocket launches. Further, the presumed location of the launches is
downgradient of the current location of the plume. There currently is no historical evidence
that would identifo the location or nature of support activities associated with the rocket
launches. If DUSA wishes to test the hypothesis that missile operations may have served as
source of nitrate contamination, then URS suggests the groundwater at the site be analyzed
for perchlorate. The Pershing rocket motors likely would have contained some amount of
perchlorate that would have been transported to the saturated zone with the other components
of the rocket fuel, if this hypothesis is correct:
Section 5.0, last paragraph: The 2005 study that is referenced supposedly cites
concentrations with units of milligrams per liter. The text characterizes the concentrations as
concentrations in soil. The units and results more likely reflect the leachable concentrations
of nitrogen measured during the leachate tests conducted on the soil samples. Please clarifo
what the concentrations of nitrate represent in this and other leachate-test discussions in the
work plan.
Section 5.1, first paragraph: URS agrees that some Geoprobe sampling of a naturally-
occurring source of nitrate in the vadose zone is warranted, but the number of borings
proposed for that investigation appears to be disproportionate compared to the number of
borings planned for potential source areas within the mill area. It is the opinion of URS that
the hypothesis of naturally-occurring deposits of nitrate and chloride in the vadose zone can
be tested with substantially fewer borings in undisturbed areas. URS will assist DUSA in
determining a statistically-based density of borings necessary to test the hypothesis that a
natural nitrogen reservoir exists at the site, if DUSA desires.
6.
7.
Page 3 of9 uxs
8.Section 5.2: URS agrees that some drilling locations are warranted. The expected maximum
number of borings should be listed in this section. Table I indicates that up to four borings
are planned. Based on the number of Geoprobe sampling locations finally determined
necessary to test the nitrogen reservoir hypothesis as recommended by URS, drilling fewer
than four borings may be warranted and can be discussed with DUSA in conjunction with the
above comment.
Section 5.2, first paragraph: URS agrees with the criterion of nitrate concentrations of "at
least twice background, based on the concentration of nitrate in near-surface soil samples" to
determine whether drilling is necessary at a location. Some flexibility should be incorporated
into this decision based on the overall results of the Geoprobe investigation. The decision to
drill should be made jointly with UDRC and should be reflected in the process flow diagram
included in the Work Plan. The decision to bore further may benefit from a calculation of the
concentration of nitrate in the soil that is expected to result in a groundwater concentration
exceeding the compliance standard for nitrate (i.e., a soil to groundwater screening level).
Unless there is a drilling objective that URS does not understand, given the relatively high
cost of drilling multiple boreholes into the consolidated formation, drilling should be avoided
if possible to focus efforts on identif,ring potential source areas rather than collecting
concentration data at depth.
Section 5.2, fourth and fifth paragraphs: URS understands that DUSA desires to test the
hypothesis that naturally-occurring deposits ofnitrate and chloride in the unsaturatedzone are
contributing to the elevated concentrations of these compounds in the saturated zone beneath
the mill. URS recommends that an additional sample be collected in the unconsolidated
interval that contains the highest concentration of nitrate, as determined by the results of the
Geoprobe investigation, for each drilling location. The additional sample should be analyzed
for nitrate isotopes in addition to the nitrate and chloride analyses via the synthetic
precipitation leaching procedure (SPLP) prescribed in the Work Plan. The characterization of
the nitrate isotopes in these deposits, if present, will assist in determining whether the nitrate
in the groundwater may have originated from the deposits.
Section 6.1: URS agrees that Geoprobe sampling around the potential source areas in the
mill area is warranted. However, two of the potential source areas listed with a high priority
for investigation in the source review report (Attachment 2 of the 2009 Nitrate Contamination
lnvestigation Report) were not included in the list of source investigation areas. These two
areas are the historic stock watering pond (near the current location of the sulfuric acid tank)
and the northern wildlife pond. URS recommends that these two areas be added to the list of
potential source areas in Section 6.1.
Section 6.1 : Including the chlorate tanks as a potential source of nitrate may be incorrect.
Based on the information in the source review report, the tanks hold sodium chlorate. If the
tanks are being investigated as a source of chloride in groundwater, they should be
characteized as a potential source of chloride. If the tanks have historically held ammonium
chlorate, then this should be noted with the entry for the chlorate tanks as a potential source
for nitrate. If the tanks have never held ammonium chlorate and are not considered a potential
9.
10.
ll
12.
Page 4 of 9 f,Iffi
13.
14.
l5
16.
source for nitrate in the groundwater based on operating records, then this potential source
area should be deleted from the list ofinvestigation areas.
Figure 2l : The red line for a potential nitrate or chloride source and the red outline for a leach
field scheduled for investigation are indistinguishable. As a result, it is not possible to
determine from Figure 2l which areas were potential sources that have been determined not
to warrant any investigation. URS recommends that the coloring for these two categories of
areas in Figure 2l be revised.
Section 6.1, fourth and fifth paragraphs: URS disagrees with the assertion that no subsurface
soil sampling is necessary at the two active leach fields if the current influent to the leach
fields is sampled. The current content of the influent to the leach fields could be very
different from the influent to the leach fields twenty or thirty years ago. URS recommends
that subsurface soil sampling should occur at these locations and should be supplemented by,
not replaced by, analyses of the influent to the leach field. Performing direct push sampling
in several locations within the unconsolidated (shallow) interval in the active leach fields will
not create preferential pathways for waste water to reach the groundwater table, particularly if
the boreholes are sealed with bentonite as stated in the Work Plan. URS agrees with the
sampling of the waste water and the use of a mass balance as outlined in this paragraph.
Section 6.1, fourth paragraph and Section 6.2 ftst paragraph: The text in these sections
appears to differ regarding which leach fields (SAG leach field or CCD/SX leach field) are
active. Please clarify.
Section 6.1: The number of proposed Geoprobe borings should be listed in this section.
Table I indicates that l3 borings are planned. This value appears to correspond to one boring
per inactive potential source area. One boring per potential inactive source area is inadequate
characterization of these areas. URS recommends two Geoprobe sample locations for each
potential source areathat was rated as a low priority in the source review report (Attachment
2 of the 2009 Nitrate Contamination Investigation Report) and four Geoprobe sample
locations for each of the sources rated as a high priority in the source review report.
However, URS acknowledges that some of these potential source areas, such as the vaults,
are relatively small. For the two low-priority vaults, one sampling location will likely be
adequate. This corresponds to one Geoprobe sampling location in each of two sites (sewage
vault/lift station and former vaulVlift station), two Geoprobe sampling locations in each of
nine areas (scale house leach field, former office leach field, ammonia tanks, Cell I leach
field, fly ash pond, chlorate tanks [assuming this area is retained], ammonium sulfate tanks,
truck shop leach field, and CCD/SX leach field), and four Geoprobe sampling locations in
each of six areas (northern wildlife pond, Lawzy Lake, Lawzy sump, the historic pond in the
location of the sulfuric acid tank, the SAG leach field, and the main leach field) for a total of
44 Geoprobe locations at potential source areas in and around the mill site. lf this total is not
achievable with the budget currently available, then priority should be given to the sources
rated as a high priority in the source review report.
Section 6.2, first paragraph: It is unclear whether the procedure for determining whether
nitrate concentrations are "elevated" is the same as that stated in Section 5.2. This section
specifies that the procedures for drilling and sampling are identical to those described in
17.
Page 5 of9 I'Rg
18.
Section 5.2, but does not explicitly state that the criteria for drilling at a location are the same.
Please clariff.
Section 6.2, first paragraph: URS agrees that the deep drilling within the vadose zone
underneath active leach fields could potentially create contaminant transport pathways to
groundwater. However, the creation of pathways may be minimized by the procedures for
backfilling the borings described in Section 5.2. URS recommends that the decision whether
to drill in the active leach fields (if elevated concentrations of nitrate are discovered in the
unconsolidated material) should be deferred pending further discussion with UDRC after
analytical data are available from the Geoprobe sampling and are assessed, rather than pre-
emptively ruling out drilling in these areas.
Section 6.2, ftst paragraph: In order to test the hypothesis that elevated concentrations of
nitrate and chloride in the unsaturaled zone due to milling activities are contributing to the
elevated concentrations of these compounds in the saturated zone beneath the mill, URS
recommends that an additional sample be collected in the unconsolidated interval with the
highest concentration of nitrate, as determined by the results of the Geoprobe investigation,
for each drilling location, and that a nitrate isotope analysis be performed on these samples in
addition to the nitrate and chloride analyses via the SPLP. The characterization of the nitrate
isotopes in these locations, if elevated concentrations are present, will assist in determining
whether the nitrate in the groundwater may have originated from these activities.
Section 6.2,frst paragraph: URS agrees that the current maximum of 13 drilling locations
should be sufficient to characterize the concentrations of nitrate and chloride in the deeper
vadose zone. Although many potential source areas have been identified, URS anticipates
that many of the potential source areas will not contain elevated concentrations of nitrate and
chloride. As previously stated, given the relatively high cost of drilling multiple boreholes
into the consolidated formation, drilling should be avoided if possible to focus efforts on
identifying source areas rather than collecting concentration data at depth.
General comment: The Work Plan should state that all Geoprobe and drilling locations will
be logged by a qualified geologist. Photographs of soil cores are recommended. The boring
logs should be recorded on a form similar to that used for borehole WMMW-16 that was
included in the as-built reports for the wells around the tailings ponds. The lithological
(boring) logs for the installation of the nitrate wells in October 2009, which were provided to
URS with the as-built report, did not fill in all of the necessary information or may not have a
location to provide necessary information, such as the sampling intervals, survey data, and
other details, and appear to inconsistently show whether the alluvial materials are
consolidated or unconsolidated.
Section 7: URS recommends identiffing additional locations for nitrate isotope analysis in
order to better characterize the source(s) of the nitrate contamination in groundwater. Only
six wells are scheduled to be sampled for stable isotopes of nitrate and water. Only two of
these are within the Mill Site -- too few to assess the nitrate sources in this area. There may
be multiple sources and locations contributing to the nitrate plume below the Mill Site. In
addition, only one of the wells (MW-3 I ) scheduled to be sampled for stable isotopes was also
sampled in the Hurst and Solomon (2008) study. Additional wells should be sampled for
l9
20.
2t.
22.l$:
Y owt
at\-1"-\
\LL
wr): *\
ha'
'r
Page 6 of9 I'NE
23.
stable isotopes that were part of the Solomon study in order to leverage the valuable
groundwater age data from that study in identiffing nitrate sources. Well MW-27 is
especially important to include since it is presumed to represent recharge from the Wildlife
Ponds. Well MW-30 should also be included to increase the coverage of high nitrate
groundwater below the Mill Site where groundwater age is known. Additionally, stable
isotope analysis should be performed at TW4-4, which is located in a separate "lobe" of the
nitrate plume and is also located within the chloroform plume. Finally, the influent to the two
active leach fields, like the slimes drain of tailings cell2, should be sampled to characterize
the isotope signature of any nitrogen compounds used in mill processing activities and
released into wastewater streams. Therefore, URS recommends that MW-27, MW-30, TW4-
4, the influent to the main leach field, and the influent to the CCD/SX leach field be added to
the list of locations in Section 7 for stable isotope analyses.
Section 7: In addition to the stable isotope analyses for groundwater, nitrate from samples of
vadose zone soils, from both undisturbed areas and potential source areas within the mill site,
should be analyzed for stable isotope composition as discussed in comments #10 and #19.
Such samples are critical for establishing the isotopic signature of nitrate sources in the
vadose zone at this site. Isotope analyses should also be conducted on l:l distilled water
leaches of core samples.
Section 7 and Table 2: Two methods that are currently used to determine oxygen and
nitrogen isotope compositions in dissolved nitrate. The first method (lon Exchange Method)
uses ion exchange columns to separate nitrate from cations present in the sample, and then
uses chemical treatments to remove sulfate and organic compounds before producing a silver
nitrate salt that is then analyzed by combustior/pyrolysis of the salt to produce N2 and CO
gas which is analyzed by isotope ratio mass spectrometry (Silva et al., 2000). The lab
identified in the work plan (Isotech) uses this Ion Exchange Method. A more recent method
(Denitrifier Method) uses a particular strain of denitriffing bacteria to produce N2O gas
from nitrate in the water sample, which is then analyzed by isotope ratio mass spectrometry
(Sigman et a1.,2001; Caciotti et a1.,2002). The study proposed for DUSA would benefit
from using a lab capable of carrying out the Denitrifier Method for two reasons. 1) The
Denitrifier Method requires much less sample volumes and lower concentrations than the Ion
Exchange Method. This will make it possible to analyze the small samples collected from
distilled water leaches from sediment core samples. 2) The Ion Exchange method can give
erroneous results for oxygen isotope compositions in nitrate if the sulfate is not completely
removed from the sample before producing the silver nitrate salt. If this occurs, both nitrate
and sulfate oxygen contribute to the oxygen isotope composition of the salt produced, thus
incorrectly identiffing the nitrate source. Interference from sulfate is a particular concern at
this study site, since sulfate concentrations are much higher than typical groundwaters.
References Cited:
Silva, S.R., Kendall, C., Wilkison, D.H., Ziegler, A.C., Chang, C.C., and Avanzino, R.J,
2000. A new method for collection of nitrate from fresh water and the analysis of
nitrogen and oxygen isotope ratios, J. of Hydrology,228:22-36.
24.
PageT of9 ung
Sigman, D.M., Casciotti, K.L., Andreani, M., Barford, C., et al. (2001) A bacterial
method for the nitrogen isotopic analyses of nitrate in seawater and freshwater. Anal.
Chem., 73, 4145-4153 .
Casciotti, K.L., Sigman, D.M., Hastings, M.G., Bohlke, J.K. et al. (2002) Measurement
of the oxygen isotopic composition of nitrate in seawater and freshwater using the
denitrifier method, Anal. Chem ., 7 4, 4905-12.
25. Section 7: It is not clear which sources will be differentiated using the isotope compositions
of nitrate. The isotopic signatures of nitrate from ammonium compounds used in processing
at the Mill Site will likely be similar to those of nitrate derived from septic effluent and
treated waste water effluent. Typically these ammonium sources have higher delta-lsN
values than natural pools ofnitrate in the soil zone, but as noted, the ranges for these sources
can also overlap in both nitrogen and oxygen isotope composition. It is likely that stable
isotope analyses of nitrate may be useful for testing the hypothesis that nitrate below the Mill
Site is due to mobilization of a natural pool of nitrate in the unsaturated soil zone vs.
contamination by an ammonium source. However, there are numerous potential ammonium
sources (wastewater effluent, septic effluent, ammonium processing chemicals), which lead
to nitrate with similar isotopic signatures. It is unlikely that stable isotope analyses of nitrate
will allow for differentiation of the various ammonium sources. Denitrification can further
complicate the use of nitrate isotope compositions for identiffing source compositions by
enriching residual nitrate in the isotopically heavier nitrogen and oxygen. The recharge from
the Wildlife Ponds identified by Hurst and Solomon (2008) may carry organic carbon into the
groundwater system where it acts as an electron donor to support denitrification.
26. Table 2: Usually one sample container can be used for oxygen and hydrogen isotopes in
water. One liter is probably more than the analytical lab will need for O and H in water.
Table 2 may need to be revised based on input from the analytical lab(s).
27. Section 7.1: Standard reference materials used by the analytical lab to calculate isotopic
values should be reported. Section 7.1 addresses the need to assess the precision of isotope A
measurements, but does not address accuracy. Use of a second laboratory for analyzing 'Yl
isotope compositions of a subset of samples would provide some additional support for thq 42
accuracy of isotope analyses. \ 0*1n '
Section 8: URS agrees with the conceptual approach of using mass balances as a line of I f tl,.r).
evidence for potential source areas. However, the comparison of the estimated mass of I - ?i,t r. ,
nitrate in the groundwater beneath the mill site to the required amount of leachate from the I ' I
tailings pond is drawn directly from the 2009 Nitrate Contamination Investigation Report. I
Since leakage from the tailings ponds has been ruled out, it would be preferable to compar. \, \"H" .. \the mass of nitrate in the groundwater beneath the mill site to the mass of nitrate that could
^ldt\'^have been delivered from Frog Pond. ln addition, an estimation of the mass of chloroform in e !- \ k
the groundwater beneath the mill site would be helptul for comparing the mass of nitrate or
Ll(atwaste water that could have been delivered to the groundwater through leach fields. . t
Figure l: URS suggest that the figure number be inserted into the title. The use of a decision C\tcVl
logic diagram is helpful, and could be included in the framework of a CSM.
Figure 3: the legibility of the values and label on the x-axis could be improved.
(P'u-t)
,.tL"'ry
trtA['fi\^', ),L,
^:fi;'
28.
29.
30.
Page 8 of 9 rtffi
31. Figure 20: The word "Missile" is misspelled on the legend.
32. Table 2: URS recommends that the planned sampling be summarized in a table showing the
sample locations; number, and types of samples for each location; the types of analyses and
the associated container type, holding time, and preservative; and the planned QA/QC
samples at pre-determined locations. Some of these details are present in Table 2, but
insufficient detail is currently presented in the table.
If you have any questions regarding these comments, please contact me at 801-904-4043 or at
paul [e-mail]. Thank you.
URS Corporation
Paul R. Bitter, P.E.
Senior Remediation Engineer
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