DRC-2012-001571 - 0901a068802e231f

State of Utah
GARY R HERBERT
Governor
GREG BELL
Lieutenant Govemor
Department of
Environmental Quality
Amanda Smith
Exeaitive Director
D[\TSION OF RADL\T!0>4 CONTROL
Rusty Lundberg
Director
DRC . 2012-00 157 1
MEMORANDUM
TO: File
THROUGH: Phil Goble, Compliance Secfion Manager
FROM: Tom Rushmg, P.G.
S ^/'^7l^
May 24, 2012
DATE:
SUBJECT Denison Mines (USA) Corp. January 12, 2012 Southwest Investigation Report for
the White Mesa Uranium Mill: DRC Review Memo
Review Summary:
This memo details the DRC review of Denison Mines USA Corp. (DUSA) January 12, 2012
Letter and Report titled, Hydrogeology of the Perched Groundwater Zone in the Area Southwest
of the Tailings Cells, Wliite Mesa Uranium Mill Site, January 12, 2012, prepared by Hydro Geo
Chem, Inc. (HGC), and signed by Licensed Professional Geologist, Stewart J. Smith (hereinafter
Report); and provides DRC comments and recommended additional information requests related
to the Report.
The Report is required by Part I.H.6 {Detailed Southwest Hydrogeologic Investigation and
Report) ofthe DUSA Ground Water Discharge Pemiit, Pemiit No. UGW370004 (Pemiit), for the
White Mesa Uranium Milling and Tailings Facility. This Pemiit requirement is cited below:
Regulatory Requirements
Pemiit Part I.H.6.
"77ze puipose of this investigation is to define, demonstrate, and characterize: 1) Hydraulic
connection and local groundwater fiow directions between the area near Tailings Cell 4B, and the
western margin of Wlnte Mesa, including West^vater, Cottonwood Seeps, and Rum Spring, and, 2)
the full physical extent of unsaturated area between former well MW-16, MW-33 and the western
margin of Wliite Mesa, as defined above. In preparation of this report, the Permittee shall
a) Install multiple borings and/or monitoring wells to completely enclose and define both
DUSA Southwest Investigation Report
DRC Review Memo
Page 2
1) Diy wells or piezometers, completed down to a depth equal to or below the upper
geologic contact of the Brushy Basin Shale Member (Monison Formation),
2) Piezometers or wells that intercept the shallow aquifer and encounter a saturation
thickness of 5-feet or more. Sqid wells and piezometers shall have a minimum
inside diameter of 3 inches. Tlie Pennittee shall complete hydrauhc testing of all
such wells and piezometers in accordance with Part LF.6(c) ofthis Permit.
b) Demonstrate the full geologic and physical extent of the apparent unsaturated structural
high between Tailings Cell 4B and the western margin of IMiite Mesa, including
Westwater and Cottonwood Seeps and Ruin Spring.
c) Demonstrate the location and direction of all groundwater fiow paths betiveen Tailings
Cell 4B and nearby Westwater and Cottonwood Seeps and Ruin Spring. Determine
average linear groundwater velocit}' to said groundwater discharge locations
d) Perfonn geologic logging of all borings/wells, and submit geologic logs performed and
certified by a Utah licensed Professional Geologist
e) Submit the investigation report for Executive Secretary^ review and approval on or before
Januaiy 13, 2012. Tins report shall be certified by a Utah Licensed Professional
Engineer or Geologist and will include but is not limited to:
1) Geologic logs and well As-built diagrams that comply with the requirements of
Part I.F.6.
2) A revised equipotential map to describe both the physical extent ofthe dry zone
and all groundwater fiow directions near Tailings Cell 4B and Westwater and
Cottonwood Seeps, and Ruin Spring. Said map shall demonstrate fiowpaths
(streamtubes) to all respective groundwater discharge locations at the western
margin of Wliite Mesa.
3) A revised structural contour map for the upper Brushy Basin Shale for the facilit}-
and physical extent of Wliite Mesa
4) A revised saturation thickness map based on contemporaneous groundwater head
data for the Burro Canyon aquifer for the facility and physical extent of HTiite
Mesa.
5) Appropriate geologic and hydrogeologic maps and cross sections (to scale).
6) Results and interpretation of aquifer permeability testing as per Part 1 F.6(c) of
this Pennit
DUSA Southwest Investigation Report
DRC Review Memo
Page 3
f) Tlie Pennittee shall provide at least a 14 calendar day written notice to allow the
Executive Secretaiy to obsene all drilling ahd well installation activities.
g) In the event the Executive Secretary determines that additional information is required,
this information will be submitted withm a time frame approved by the Executive
Secretary.
Dry Well Monitoring Network Installation and Initial Water Level Monitoring
Twenty two boring locations were located and drilled by DUSA within the study area:
1. Dnlling and well construction was performed by Bayles Exploration Inc.
2. An initial 6 VA inch diameter tricone bit was used to drill to a depth of approximately five
feet below land surface.
3. A 6 inch diameter PVC surface casing was installed to a depth of approximately five feet
below land surface.
4. Boreholes were then drilled by air rotary using 5 5/8 to 6 1/8 inch diameter tricone bits
(the Report notes that water and/or foam were added when needed).
5. All boreholes penetrated the Dakota Sandstone and the Burro Canyon Formation and
terminated in the Brushy Basin member of the Morrison Formation.
6. Drill cutting samples for lithologic logging were collected at 2 Vz foot depth intervals and
placed in labeled, zip sealed plastic bags and labeled plastic cutfings storage boxes.
7. Borings were logged by Mr. Lawrence Casebolt (Report includes copies of lithologic
logs).
8. The 6 inch surface casings were capped and the open bonngs were left open. Note that the
open bormgs were sequentially numbered and included the prefix DR (Dry Ridge).
9. Water levels were "periodically" taken over approximately 1 month.
10. Decisions were made to abandon 4 of the open borings:
a) DR-2 was abandoned based on "Z)/?-5 provided similar infonnation'"'
b) DR-16 was abandoned based on several other monitoring wells and borings in
close proximity, DR-16 did not appear to add significant information
c) DR-18 was abandoned based on remaining dry
d) DR-25 (due nortii of Ruin Spring, closest proximity) was abandoned based on not i
providing significant information
J1. Borings, which were not abandoned, had piezometers completed using 3 inch diameter
PVC casing and 0.02 slot (factory slotted) PVC screens. Colorado Silica Sand was used as
a filter pack and installed approximately three to six feet above the slotted screened
interval.
12. The reniaining amiular space was sealed with eight feet of hydrated bentonite chips then
grouted to surface using Portland cement.
DUSA Southwest hivestigation Report
DRC Review Memo
Page 4
Water Level Data Summary/DRC Findings
HGC shows two dry zones within the study area on water level maps included with the Report
(Perched aquifer water levels for the 2"^^ and 3''' Quarters of 2011). Per the Report, '"The diy
areas ...occur where the kriged contact between the burro Canyon Formation and the Brushy
Basin Member is higher in ele\'ation than the kriged perched water elevation.'''' The water level
elevation maps and Figure 9 of the Report (Axes of Brushy Basin Paleondges and Paleovalleys)
also delineate areas which have a saturated thickness less than 5 feet and a saturated thickness
greater than 10 feet (areas are delineated by plotted hatch marks on the aenal photo). HGC states
that Figure 9 complies with the requirements of the Permit Part I.H.6.b. and e., items 2, 3 and 4.
Per the HGC conclusions in the Report, ''paleondges in the southwest area of the site are
associated with areas of higher saturated thicknesses. Westvi'ater Seep and Ruin Spring are
located in paleovalleys. (Cottonwood Seep is not directly connected to the perched water system,
and the likely source for Cottonwood Seep is Wesnvater Creek...).''
HGC additionally notes "an apparent perched water divide exists in the vicinity of DR-2 and DR-
5 (Figure 6). Perched water north of this divide is expected to fiow northeast toward Wesnvater
Seep and perched water south of this divide is expected to fiow south toward Rum Spring.
DRC notes that boring DR-02 was abandoned, the basis of which was that boring DR-05 supplied
similar infomiation, however DR-02 is the westem most bonng m the direct vicinity of the HGC
anticipated hydraulic divide. The saturated thickness of the perched aquifer in the area of DR-05
and DR-02 is greater than 10ft. It appears that additional borings need to be conducted farther
west from DR-02 to investigate the thickness of the saturated zone north/north-west of
Cottonwood Seep. Per Figure E.2 of the Report, the Burro Canyon Formation outcrops continue
approximately 0.8 mile west of Westwater Seep (approximately 0.5 miles west of abandoned
boring DR-02). Additionally, Figure E.2 of the report shows a significant area of slumps and
landslides which extend even farther to the west. These areas of Burro Canyon outcrops and
landslides are directly north of Cottonwood Seep.
DRC Notice of Enforcement Discretion
The abandonment of borings DR-02, DR-16, and DR-25 was in violation of the Permit Part
I.H.6(a)2. which requires hydraulic testing of all wells and piezometers with a saturation thickness
of 5-feet or more.
DRC will provide enforcement discretion for these violations, based on DUSA's agreement to
conduct additional borings and install additional piezometers in the vicinity of and west of
abandoned boring DR-2. ^
i
DUSA Southwest Investigation Report
DRC Review Memo
Page 5
Hydraulic Testing Method
1. All DR piezometers with at least 5 feet of water in the casings were hydraulically tested
using falling head slug tests, and were conducted by Hydro Geo Chem. Inc. (HGC). (DRC
notes that contrary to this, tliree abandoned borings which had more than five feet ofwater
were not hydraulically tested),
2. The slugs used for the tests consisted of sealed, pea gravel filled, PVC pipe approximately
4 feet long and a slug of the same diameter with a length of 3 feet
3. Three Troll data loggers were used for the tests:
a) One Troll was used to measure barometric pressure and was placed in a protected
environment for the duration of the testing (report did not specify where the Troll
was located)
b) The other two Trolls were deployed below the static water columns in the tested
wells and used to measure water level changes during the tests
4. Automafically logged water level data were collected at 3 second intervals and barometric
data at 5 minute intervals.
5. Static water level was measured using an electric water level meter
6. Troll was lowered to a depth of approximately one foot above the base of the well casing
and background pressure readings were collected for approximately 30 minutes to allow
corrections for any detected water level trends.
7. The slug and electric water level meter were suspended in the tested well just above the
stafic water level.
8. A series of tests occurred by lowering the slug to a depth of approximately 1-2 feet below
the static water level over a period of a few seconds and taking water level readings with
the electric meter as soon as possible afterwards.
9. The hand collected data was obtained more frequently in the first few minutes then less
frequently as the rate of water level change diminished.
10. The Troll logged data were checked and backed up after each series of tests for the well.
Hydraulic Test Results Summary/HGC Evaluation/DRC Findings
Hydraulic testing was performed at the following piezometers; DR-5, DR-8, DR-9, DR-10, DR-
11. DR-13, DR-14, DR-17, DR-19, DR-20, DR-21, DR-23, DR-24. ResuUs ofthe slug tests are
mcluded as Table 3 of the Report. Per the methodology descnbed in the section above, HGC
collected two groups of data, automatically logged using a transducer, and hand collected using a
water level meter attached directly to the slug. The data was analyzed using two methods, the
Kansas Geological Survey Model with Aqtesolve which allows calculafion of K and Ss, and the
Bouwer-Rice method which allows the calculafion of K only. DRC notes that filter pack
interferences regarding the tests should be taken account of by mathematical method, accounting
for filter pack as part of the well diameter. HGC notes in the report that when calculation required
inputs for filter pack porosity, a value of 30% was used.
Estimates of hydraulic conductivity range from 3.4 x 10"^ cm/s to 4.5 x 10~^ cm/s using the
automatically logged data, and from 1.0 x 10"^ cm/s to 4.7 x 10"^ cm/s using hand-collected data.
DUSA Southwest Investigation Report
DRC Review Memo
Page 6
HGC states in the Report, ''Agi'eement between analyses using the KGS and Bouwer-Rice
solution, and between automatically-logged and hand-collected data was generally good Except
for DR-8 all KGS and Bouwer-Rice estimates using automatically logged data were within a
factor ofhvo, and the majorit}' was within 30%j. KGS and Bouwer Rice estimates using hand-
collected data were withm a factor of three, and the majority was also within 30%. Agreement
behveen KGS solution estimates using automatically logged and hand-collected data were within
a factor ofnvo except for DR-8 and DR-10 which were within a factor of three.'''
DRC notes that the slug test results for piezometer DR-8 differ by an order of magnitude between
the automatically logged data and the hand collected data. DRC additionally notes that Table 3
lists, ''Not Interpretable" as the K value at DR-8 by the Bouwer-Rice Method using the Hand
Collected data. Slug tests at piezometer DR-8 need to be repeated in order to support K values
which are lower than average K values (2.3 x 10 ' to 4.3 x 10'^ cm/s per Section 3.11, p. 10 of the
. Report) by 3 orders of magnitude.
HGC concludes in the Report section 2.3 "Tlie results of the testing mdicate that hydraulic
conductivities in the southwest portion of the site are lower than pre\nously estimated indicating
perched water moves more slowly than previous calculations would indicate.'''' HGC additionally
finds that the higliest permeability was measured in wells "immediately northeast and east
(upgradient to cross gradient) of the ladings celF and that permeability of wells downgradient of
the tailings cells are generally low with average K values of 2.3 x 10'^ to 4.3 x 10"'^ cm/s.
HGC Southwest Hydrogeology Overview Based on Data Collected
Section 3 ofthe Report discusses the HGC findings and interpretation of the hydrogeology of the
Southwest area, including interpretations of sources of flow to Westwater Seep, Cottonwood Seep
and Ruin Spring.
Seeps and Springs
1. Cottonwood Seep is interpreted to originate from coarser-grained materials within the
lower portion ofthe Brushy Basin Member of the Morrison Fomiation and are not
connected to the perched Burro Canyon Aquifer,
2. Ruin Spring and Westwater Seep are associated with conglomeratic portions ofthe Burro
Canyon Formation, since those portions of the Burro Canyon are likely to have higher
permeability and the ability to transmit more water,
3. Ruin Spring appears to receive a predominant portion of its flow from the perched water
Burro Canyon Fm., and Westwater Seep receives a significant proportion from perched
water.
4. All seeps and springs "are reported" to have enhanced flow dunng wet penod which is
consistent with flow from alluvium (alluvium is associated with all but Ruin Spnng), in
DUSA Southwest Investigation Report
DRC Review Memo
Page 7
the case of Ruin Spnng this enhanced flow is likely due to recharge of Burro canyon
Formation and Dakota Sandstone outcropping near the vicinity of Ruin Spnng.
5. Cottonwood Seep is located at the contact between the Westwater Canyon Member and
the Brushy Basin Member of the Morrison Fonnation.
6. Tlie likely source of water to coarser grained materials in the lower Brushy Basin Member
or Westwater Canyon Member which feeds Cottonwood Seep is Westwater Creek.
Cross Sections
Figures 10 and 11 of the Report are cross sections depicting the saturated thickness of the Burro
Canyon Aquifer and contact elevations of the Brushy Basin Fm. HGC delineates "dry zones" on
Figure 9, zones where the Brushy Basin Contact is higher than ground water elevations and
proposes that thicker saturated zones wliich are apparent to the west of these dry zones must be
explained by local recharge of aquifer by precipitation.
HGC proposes that margin areas of the Mesa where Dakota Sandstone and Burro Canyon
Formation is directly exposed allows for more recharge to these zones due to the absence of
overlying low pemieability materials such as Mancos Shale.
DRC notes that HGC discounts areas southwest of Westwater Seep as a potential recharge zone
for Cottonwood Seep, however, this area encompasses a large area of exposed Burro Canyon
Formation as well as an area of landslides which are directly north of Cottonwood Seep HGC
argues that the zone is inadequate to recharge Cottonwood Seep based on water balance
calculations near piezometers DR-2 and DR-5. Calculations for groundwater flow are compared
for areas of low saturated thickness at piezometers DR-10 (using KGS K values) and the zone of
higher saturated thickness at piezometer DR-5, which show a difference between calculated
inflow and outflow of 0.016 gpm.
Perched Water Flow Directions
The Report Figure 12 is a water elevation contour map which includes inferred flow lines for the
perched water based on the plotted contours. HGC proposes that there is a hydraulic divide in the
area of DR-2 and DR-5 wherein all groundwater flow north of the divide flows to Westwater Seep
and water south of the divide flows south along the mesa margin to Ruin Spring. DRC notes that
the hydraulic divide is not supported by adequate field data. The Burro Canyon outcrop extends
westward from the last used water elevation data, DR-5, for approximately Vz mile. Therefore, in
order to substanfiate the divide, additional water elevation data needs to be obtained in these areas
to extend the water elevation contours.
DUSA Southwest Investigation Report
DRC Review Memo
Pages
Perched Water Travel Tunes
Figure 13 of the Report evaluates travel times in the perched aquifer from the margm of cell 4B to
Westwater Seep and Ruin Spring. Travel times to Cottonwood Seep were not calculated based on
the Report findings regarding perched water flow directions as discussed above. Based on this,
HGC calculates travel times based on 3 flowlines which are plotted on Figure 13; A flowline from
the northwest comer of Cell 4B to Westwater Seep (Path 1), A flowline from the southwest comer
of Cell 4B to Ruin Spring on the west side of the "dry zones" as defined in the report (Path 2), and
a flowline from the southwest comer of Cell 4B to Ruin Spring on the east side ofthe "dry zones"
(Path3).
Hydraulic gradients were calculated based on 3^*^ quarter 2011 groundwater elevation data for
monitoring wells at Cell 4B and the elevation of Westwater Seep and Ruin Spring. Hydraulic
conducfivity was based on the geometric mean of a set of data (monitoring wells and DR
piezometers) in the pathline area. Effective porosity used for all calculations was 0.18. Based on
the calculations the following travel times were calculated by HGC:
Path 1 - 2,500 years
Path 2- 17,900 years
Path 3- 10,900 years
DRC cross checked the HGC calculated travel times for each ofthe paths in the Report
(calculafions included as Attachment 1 of tliis memo). Per the DRC cross check it appears that all
calculations are correct based on the HGC inputs to formulate the calculations. DRC does note
1he following potential issues related to the calculafions:
1. Hydraulic gradient is calculated based on elevafions which are very distant from one
another (eg 11,800 feet for Path 2). There could be several distinguished gradients along
the path line which would make travel times shorter along certain segments and longer on
others. DRC did not evaluate the validity of using an average gradient along these long
flow paths.
2. The calculations do not account for potential heterogeneity of porosities within the
saturated zone, there may be zones of higlier permeability (lower K) which could decrease
transport time significantly. DRC does note that HGC used all data wliich was available in
the area.
3. HGC used the hydraulic parameters from piezometer DR-08 to calculate the average K
used in the calculations. These calculations do not seem reliable at this well based on
vanation of results and DRC is requesting that the hydraulic tests be repeated to validate
the data results.
DUSA Southwest Investigation Report
DRC Review Memo
Page 9
Summary of the Report Conclusions made by HGC:
In general the HGC conclusions in the Report are:
1. Hydrogeology in the Southwest area of the Mill is characterized by low permeability and
shallow hydraulic gradients, HGC calculated average pore velocities along three path
lines, considered representative, indicate values of 0.55 ft/yr to 0.89 ft/yr. HGC concludes
that the perched water flow is greatly influenced by the Bmshy Basin erosional surface in
the Southwest portion of the site due to low saturated thickness and dry zones in the area.
2. Westwater Seep and Ruin Spring are both located in paleovalleys within the Bnishy Basin
paleosurface and are sourced by the perched zone. Local recharge is needed to explain
areas of large saturated thickness that supply Westwater Seep and Ruin Spring, due to an
inadequate recharge calculation from low saturated thickness portions of the perched zone.
3. Cottonwood Seep is not directly connected to the perched water system and the source of
Cottonwood Seep is likely Westwater Creek to the nortli/northeast. It is hypothesized that
coarser grained layers within lower portions of the Brushy Basin Member or the upper
portion of the Westwater Canyon Member are providing a hydraulic conduit between the
Westwater Creek and Cottonwood Seep and that the coarser grained layers are being
recharged by Westwater Creek upgradient from Cottonwood Seep.
4. Based on the hypothesized hydraulic connection between Westwater Creek and
Cottonwood Seep, perched water from Westwater Seep which discharges into the
proposed recharge zones of Cottonwood Seep, could potentially flow downgradient to
Cottonwood Seep, but would be a negligible contribution to the discharge.
DRC Review for Compliance with the Permit Requirements and Data Gaps/Request for
Additional Information
Several data gaps exist to comply with the Pemiit requirements of Part I.H.6 and to support
findings in the report. These data gaps are:
1. The Report does not provide definitive evidence to support a hydraulic divide in the area
of piezometer DR-05 and the abandoned borehole DR-02, as required by the Part I.H.6.C
ofthe Permit. Flow path lines as depicted on Figure 12 of the Report west of piezometer
DR-05, which discount westerly flow toward Cottonwood Seep, are not supported with
measured groundwater elevations and plotted contours that extend into this area. The
Report data shows relatively significant saturated thickness, > 10 ft, measured at
piezometer DR-05 and bonng DR-02 (prior to abandonment), but does not provide field
data to detemiine how far west the zone of saturation extends or to provide hydraulic
evaluation of that zone which is supported by data. Additional borings and study are
needed to better characterize flow and hydrogeology of the perched aquifer in the area
west of abandoned boring DR-2 (southwest of Westwater Seep) and to substantiate the
DUSA Southwest Investigation Report
DRC Review Memo
Page 10
statement in the Report that this area is "inadequate as a potential supply to Cottonwood
Seep (p. 19)" (HGC statements are based on water balance results for DR-10 and DR-5
only). Per Figure E.2 of the Report, the Burro Canyon Formation outcrops continue
approximately 0.8 mile west of Westwater Seep (approximately 0.5 miles west of
abandoned bonng DR-02). Addifionally, Figure E.2 of the report shows a significant area
of slumps and landslides which extend even farther to the west. These areas of Burro
Canyon outcrops and landslides are directly north of Cottonwood Seep and warrant
additional physical and hydraulic investigation prior to discounting them as a source of
recharge.
2. The Report, Table 3, lists slug test results (K and Ss) for the investigation completed
piezometers. DRC notes that the slug test results for piezometer DR-8 differ by an order
of magnitude between the automatically logged data and the hand collected data. DRC
additionally notes that Table 3 lists, "Not Interpretable' as the K value at DR-8 by the
Bouwer-Rice Method using the Hand Collected data. This data appears suspect. Slug
tests at piezometer DR-8 need to be repeated in order to support K values which are lower
than average K values (2.3 x 10'^ to 4.3 x 10"^ per Section 3.11, p. 10 of the Report) by 3
orders of magnitude.
3. The Report states that Cottonwood Seep is located at the contact between the lower Brushy
Basin and Westwater Canyon Fomiation but does not provide figures on an appropriate
scale to support tliis claim as required by the Permit Part I.H.6.e.5. The Report provides:
a. Figure 3 of the Report is a photograph (no scale indicated) with dashed
approximation lines of the fomiation/member contacts. Figure 3 does not provide
measured elevations of the contacts to verify that thicknesses ofthe
formations/members are consistent with regional measurements (e.g. Brushy Basin
Member is approximately 300 ft (90 m) thick in the Study area per UGS
descriptions"), and to cross check with location geologic maps.
b. The Figure E.2. geologic map of the area does not include contact elevations. A
geologic map is required by Part I.H.6.e.5 which shows outcrop locations and
elevations throughout the Westwater Creek drainage, on an appropriate scale, and
which supports the Report claims that Cottonwood Seep originates from "coarser-
gramed materials withm the lower portion of the Brushy Basin Member'" or
"alternatively, Cottonwood Seep may originate from coarser-grained materials of
the Weshvater Canyon (sandstone) Member intertongueing with the overlying
Brushv Basin Member at the transition behveen the hvo Members" (Report section
4.2, p; 22).
4. The Report does not provide evidence to support the claims of a hydraulic connection
between Westwater Creek and Cottonwood Seep as required by the Pemiit Part I.H.6.C.
The Report Figure 16, delineates an area which HGC interprets as the likely source of
DUSA Southwest hivestigation Report
DRC Review Memo
Page 11
Cottonwood Seep based on elevation, however no additional infomiafion is provided to
support the hydraulic connection. Such evidence is required to include:
a. Evidence of a continuous zone of liigher pemieability connecting the likely source
area of Westwater Creek with Cottonwood Seep (e.g. boring logs showing the
coarser grained or sandstone layer),
b. Delineation of stream alluvium deposits within the Cottonwood Creek drainage and
especially within the proposed likely stream segment of Cottonwood Seep (to
understand the actual zones of influence),
c. Average flow in the Westwater Drainage,
d. A detailed evaluation/explanation of the hydraulic mechanism promoting flow into
the hypothesized higlier pemieability layer, instead of stream bed flow.
DRC will request that DUSA provide a revised Report which addresses all items listed above as
per agreed upon timelines. It is reconimended that DRC and DUSA discuss the issues and agree
upon timelines during a conference call.
DUSA Notification of Drilling Activities
DRC will require DUSA to provide at least 14 business day notification prior to any dnlling
activities in the field in order to provide an opportunity for DRC staff to observe such activities.
Comparison of HGC Conclusions witb a 2011 USGS Report
The conclusions of the Report were compared with a 2011 study document prepared by the U.S.
Geological Survey^ (Study) which included water collection and analysis from multiple seeps in
the area, including Westwater Seep (referred to as Mill Spring in the Study), Cottonwood Seep
(referred to as Cow Camp Spring in the Study), and Ruin Spring. DRC notes that the analysis
results for Oasis Spring and Entrance Spring were also useful for analyzing potential recharge
sources of Westwater Seep. Analysis was conducted for cation/anion chemistry as well as
isotopic ratios in order to characterize the chemical properties and age of the water collected at
each source. The study includes numerous plots and diagrams which compare the results for
water collection at each of the sources.
Per DRC review of the Study, and in relation to the Southwest hivestigation the following
observations were noted:
1. The Study p. 22 "Waterfrom Cow Camp Spring had an apparent age of 12 to 19years
Both Oasis and Entrance Springs had water with recent apparent ages. Cow Camp Spring
was the only site that yielded 'Hcuit or dissolved helium derived from tritium decay, which
allowed for calculation of apparent age by using the ratio of^Heun to '^H in the water
DUSA Southwest Investigation Report
DRC Review Memo
Page 12 '
Sites categorized as recent have detectable amounts of^H but no '^Hcmt which results m a
calculated apparent age equal to zero.
2. The Study p. 67 "Tritium/helium age-dating of water samples collected from Cow Camp
Spring, Oasis Spring, and Entrance Spring yielded apparent ages of recent to 18 years.
Tins apparent age indicates a localized and potentially induced fiow path from artificial
recharge to the surficial aquifer."
3. The age dafing of water samples at Westwater Seep and Ruin Spring showed ages greater
than 50 years.
4. Piper diagrams in the Study indicate a tight patterning of constituents for Westwater Seep
and Ruin Spnng with calcium sulfate bicarbonate water signature; Cottonwood Seep show
a differentiation in water chemistry with a sodium calcium sulfate signature. Oasis Spring
and Entrance Spring show a calcium bicarbonate sulfate water signature.
'i
DRC notes that the geologic contact points for the Springs was not considered in the s
Study. It appears that an assumption was made that Westwater Seep, Cottonwood Seep,
Ruin Spmig and Entrance Spnng all originate from the base of the Burro Canyon Contact
with the Bmshy Basin.
The Study indicates that water collected at Cottonwood Seep was younger than water collected at
either Westwater Seep or Ruin Spring, but older than water collected at Oasis Spring or Entrance
Spring, which are known to have localized recharge. Water chemistry at Cottonwood Seep shows
cation/anion chemistry which appears distinct from the other seeps/springs.
References
' Hydro Geo Chem Inc., January 12, 2012, Hydrogeology of the Perched Groundwater Zone in the
Area Southwest of the Tailings Cells WTiite Mesa Uranium Mill Site, Prepared for Denison Mines
(USA) Corp.
^ Titan Environmental, July 1994, Hydrogeologic Evaluation of Wliite Mesa Uranium Milf
Prepared for Energy Fuels Nuclear Inc.
^U.S. Geological Survey, 2011, Naftz, D.L., Ranalli, A.J., Rowland, R.C, and Marston, T.M.,
Assessment of potential migration of radionuclides and trace elements from the Wliite Mesa
uranium null to the Ute Mountain Ute Resen'ation and sun'ounding areas, Southeastem Utah:
U.S. Geological Survey Science hivestigations Report 2011-5231, 146 p.
"^Utah Geological Survey, 2008, Stefan Kirby, Geologic and Hydrologic Characterization of the
Dakota-Bwro Canyon Aquifer near Blanding, San Juan County, Utah
Attacliment 1
DRC Venfication of HGC Report Pathlines, Velocity and Travel Times
DRC Review of Transport Times for the three Transects lnclude(d in the HGC January 12, 2012 Southwest Investigation Report
Gradient:
From Well No. to Spring Path # in
Report
GrouncJwater Elevation
(feet amsl)
Hydraulic Head
Difference (ft)
Distance
Between Wells (ft)
Groundwater
Gradient (ft/ft)
MW-23 to Westwater Seep 1 5498 to 5468 30 00 2200 0.0136
MW-36 to Rum Spring 2 5493 to 5380 113 00 11800 0 0096
MW-37 to Rum Spring 3 5490 to 5380.00 11000 9685 0.0114
Groundwater Velocity*:
K (cm/sec) gra(dient
Velocity
(cm/esc)
Velocity
(ft/day)
Velocity
(ft/year)
-
Path 1 , 1.15E-05 0.0136 8.7E-07 0.0025 0.90 -
Path 2 1.22E-05 0.0096 6.5E-07 0.0018 0.67
Path 3 1.38E-05 0 0114 8.7E-07 0.0025 0.90
Assumes effective porosity of 0.18
Travel Time Along Path:
Path 1 = 2447 years
Path 2 = 17528 years
Path 3 = 10710 years