DRC-2020-012800 - 0901a06880ce33e4

Energy Fuels Resources (USA) Inc.
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228
303 974 2140
www.energyfuels.com
ENERGY FUELS
July 20, 2020 D C-2.,o7.0 -0 I 2.000 Div of Waste Management and Radiation Control
JUL 2 2 2020 Sent VIA E-MAIL AND EXPEDITED DELIVERY
Mr. Ty L. Howard
Director
Division of Waste Management and Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
P.O. Box 144850
Salt Lake City, UT 84114-4820
Re: Response to Utah Division of Waste Management and Radiation Control ("DWMRC")
Request for Additional Information (RAI) regarding the Energy Fuels Resources (USA)
Inc. ("EFRI"), May 8, 2020 White Mesa Uranium Mill Low-Flow Sampling Plan Utah
Groundwater Discharge Permit No. UGW370004
Dear Mr. Howard:
This letter responds to DWMRC's letter dated May 27, 2020 regarding the DWMRC Request
for Additional Information ("RAI") regarding the EFRI, May 8, 2020 White Mesa Uranium Mill
Low-Flow Sampling Plan.
For ease of review, the DWMRC comment or request has been repeated in italics, below,
followed by EFRI' s response.
A redline (of the text modifications only) and clean copy of the Low-Flow Sampling Plan are
attached to this letter.
DWMRC Comment
RAI — Cited Low Flow Guidance in the EFR Plan needs to be Updated and Discussed
The EFR Plan cites three references regarding low flow sampling including: 1) Low Flow Minimal
Drawdown) Groundwater Sampling (Puls and Barcelona 1996); 2) Groundwater Sampling
Guidelines for Supeifund and RCRA Project Managers (Yeskis and Zavala 2002); and 3)
EQASOP-GW4, Region 1 Low Stress (Low Flow) SOP Rev 4 (EPA 2017). The EFR Plan states
that these guidance references limit the use of low flow sampling to monitoring wells with screen
lengths less than 10 feet and inside diameters 1.5 inches and greater. Per DWMRC review of the
EPA 2017 SOP it was noted that the criteria cite the Puls and Barcelona 1996 guidance, which
was an EPA contracted study. Therefore, the EPA 2017 SOP is limited to the 1996 findings and,
per DWMRC review, additional study was conducted after the 1996 guidance which updated those
Letter to Ty L. Howard
July 20, 2020
Page 2 of 4
findings and found that low flow sampling is appropriate and representative of longer well screen
lengths.
Specifically, M.J. Barcelona, M.D. Varljen, R.W. Puls and D. Kaminski, Winter 2005, Ground
Water Purging and Sampling Methods: History vs. Hysteria, Ground Water Monitoring &
Remediation 25, no. 1/pp 52-62 states that monitoring wells should not be prohibited from low
flow sampling based on well screen lengths alone.
The use of low flow monitoring and representativeness in the case of longer well screens is based
on a site and/or well basis. Therefore, an objective of the EFR Plan and study is to detennine the
suitability of the White Mesa monitoring well designs and aquifer properties for low flow sampling.
This evaluation is needed based on the erroneous (high ) dissolved oxygen readings at several
monitoring wells and, as was noted in the EFR Plan, the current groundwater purge collection is
likely introducing air into samples based on the fully penetrating well screens, perched aquifer
hydraulic properties, and small saturated thickness at several wells, which results in significant
agitation of the groundwater sample at affected monitoring wells. Low flow sampling comparisons
with standard purge samples should provide more information regarding the reliability of
monitoring results in the event of sample agitation/aeration during purging. Specifically, sample
comparison will be used to determine whether the sample agitation affects data results.
Please modify the discussion of literature citations to include more recent studies of low flow purge
and appropriate screened intervals based on the data results. Again, all conclusions regarding the
appropriateness of the low flow method for monitoring wells at the White Mesa Mill should be
based on the Mill specific sampling and data evaluation. The objective of the low flow monitoring
study is to evaluate whether there are data impacts due to sample aeration during standard (2
casing volume) purging activities.
EFRI Response:
The citation has been added to the Low-Flow Sampling Plan as requested. A brief summary of
the new reference has been added t the text of the Low-Flow Sampling Plan.
DWMRC Comment
RAI — EFR Plan Well Set Needs to be Expanded and Representative of Mill Groundwater
The EFR Plan states that the three upgradient monitoring wells MW-01, MW-18 and MW-19 will
be used for the study. The EFR Plan states that these wells are appropriate for the study based on
"a wide range of both hydraulic conductivities and DO results." Per DWMRC review, this small
well set does not represent sitewide monitoring wells and does not adequately address issues
where DO measurements greater than 100% were found.
Please modify the well set to include a representation of sitewide monitoring wells, including the
compliance well monitoring wells where significant agitation/oxygenation of groundwater
samples was found (>10% DO). Per the discussion between DWMRC, EFR and Hydro Geo Chem
on May 18, 2020 it was decided that a set of 10 monitoring wells or more is adequate to address
Letter to Ty L. Howard
July 20, 2020
Page 3 of 4
the study objectives. EFR discussed that the wells would be evaluated to determine which ones
show relatively high DO measurements and have local aquifer hydraulic properties favorable to
low flow purging parameters (e.g. will not be susceptible to excessive drawdown).
EFRI Response:
In response to the DWMRC RAI, EFRI has expanded the scope of the Low-Flow Sampling Plan
to include 10 wells. Specific details regarding the wells and the reason for their inclusion are
included in Section 5.0 and Table 5.0 of the Low-Flow Sampling Plan.
It is important to note that while DWMRC requested that all wells have DO>10%, two wells with
DO measurements <10% have been included. These wells were included to provide a complete
data set and the data will be used to assess if any noted analytical differences are due to DO and
sample agitation or due to the different sampling methodologies. Including wells from the full
range of DO measurements will allow for a definitive determination of the causes of any analytical
differences if present. Without the low DO data, it is not possible to completely assess the data
and draw definitive conclusions regarding the effects of agitation versus sampling methodology
differences.
DWMRC Comment
Samples by Both Methods need to be Collected at the Same Time for Data Comparison
Evaluation of the monitoring results will require the comparison of analytical data (all field,
compliance and background constituents) between the two collection procedures (low flow and
standard 2 casing volume purge). In order to provide comparable data, the samples by each
method will need to be collected at the same time (low flow sample followed by purge sample).
The current method included in the EFR Plan is not acceptable for this purpose. The EFR Plan
states that the three upgradient monitoring wells listed above will be used for the study and will
be collected by the different purge methods during completely different quarterly sampling.
Specifically, the EFR Plan outlines a method of collecting purge samples during the compliance
quarters (Semi-Annual Sampling is required at the Upgradient Wells by the Groundwater Permit),
and low flow samples during the other quarters. This will not provide comparable results.
Based on the expanded monitoring well set discussed in the RAI above, please include a plan for
sample collection by low flow and standard purge (2 volume) at the same time (collected
contiguously).
EFRI Response:
The sampling methodology has been modified as requested. The volume-based sampling will be
conducted immediately following the low-flow sampling.
DWMRC Comment
EFR Data Summary and Evaluation Clanfication Needed
Letter to Ty L. Howard
July 20, 2020
Page 4 of 4
The EFR Plan only includes a statement that data will be summarized in a final report (EFR Plan
9.0). Please include a discussion in this section generally presenting how the data will be
evaluated, summarized, and submitted by EFR.
EFRI Response:
EFRI has added details regarding the assessments of the data that will be completed in the final
report. Specific details regarding statistical methods will be determined after the data are received
based on what is appropriate for those data. Specific methods will be discussed in the final report.
In addition, the justification for those methods will be included.
Please contact me if you have any questions or require any further information.
Yours very truly,
ENERGY FUELS RESOURCES (USA) INC.
Kathy Weinel
Quality Assurance Manager
cc: Dave Frydenlund
Paul Goranson
Logan Shumway
Terry Slade
Garrin Palmer
Scott Bakken
REDLINE
White Mesa Uranium Mill
Low Flow Sampling Plan
State of Utah
Groundwater Discharge Permit No. UGW370004
Prepared by:
eFENERGY FUELS
Energy Fuels Resources (USA) Inc.
225 Union Boulevard, Suite 600
Lakewood, CO 80228
May-8,July 20, 2020
Contents
1.0 INTRODUCTION 1-1-
2.0 BACKGROUND 2-1-
3.0 GEOLOGY/HYDROGEOLOGY 32
4.0 EPA GUIDANCE FOR LOW FLOW SAMPLING 44
5.0 WELLS INCLUDED IN THIS PLAN 65
6.0 PROCEDURES 75
6.1 Volume-Based Purging Method 76
6.2 Low Flow (Minimal Purge) Sample Method 86
6.2.1 Low Flow Well Purging: 86
6.2.2 Low Flow Well Sampling 97
7.0 QUALITY CONTROL ("QC") SAMPLES 97
8.0 SCHEDULE 108
9.0 REPORTS 108
10.0 REFERENCES 129
1.0 INTRODUCTION
Part I.E.1.d.1, of the State of Utah Groundwater Discharge Permit ("GWDP") dated March 19,
2019, required the addition of Dissolved Oxygen ("DO") to the list of field parameters collected
during groundwater purging. As required by the March 19, 2019 GWDP, Energy Fuels
Resources (USA) Inc. ("EFRI") revised the Quality Assurance Plan ("QAP") to include the
collection of DO during purging. EFRI submitted Revision 7.6 of the QAP for the Division of
Waste Management and Radiation Control ("DWMRC") approval on August 22, 2019.
DWMRC approved Revision 7.6 of the QAP by letter dated September 10, 2019. DO
measurements commenced in the third quarter of 2019. No DO measurements were collected
during the second quarter 2019 groundwater sampling program because the second quarter
sampling program was completed prior to the receipt of the DWMRC's approval of Revision 7.6
of the QAP.
EFRI submitted the third quarter groundwater report on November 13, 2019. By letter dated
January 13, 2020, DWMRC stated that it appeared all applicable requirements of the GWDP
were met, and that the submitted groundwater monitoring data were reliable, and the review was
closed.
The DWMRC letter dated January 13, 2020, noted that several DO monitoring well results were
above 100% oxygen saturation and that the results were greater than DWMRC expected in area
groundwater. DWMRC and EFRI discussed the third quarter results by conference call on
December 11, 2019. Initial evaluation by the EFRI consultant (HydroGeoChem) discussed that
oxygen was likely introduced into the samples due to the low permeability and small, saturated
thickness of the perched aquifer combined with agitation during purging and sampling. Section
2.0 below summarizes the previously submitted EFRI concerns regarding DO measurements and
the limited usability of those data. Per discussion with DWMRC, it was agreed that additional
evaluation would be conducted by EFRI to determine potential effects of the sample
oxygenation, and evaluation of alternate micro-purge/low-flow sample collection to evaluate the
impact of DO in the groundwater samples. EFRI agreed to submit a plan for low flow sampling,
including a planned date for a final report submission to DWMRC for review and approval, on or
before April 9, 2020. The deadline for submission of the plan was extended to May 9, 2020 due
to COVID-19 issues and teleworking requirements. Revision 0 of the Low-Flow Sample Plan
was submitted to DWMRC on May 8, 2020.
This plan is being submitted to meet the requirement for a plan to assess low flow sarnpling at
the White Mesa Mill (the "Mill").
DWMRC provided written comments and a Request for Additional Information ("RAI") to the
Low-Flow Sample Plan to EFRI by letter dated May 27, 2020. The RAI requested a revised
Low-Flow Sample Plan be submitted by EFRI on or before July 20, 2020. This plan is being
submitted to address the comments in the May 27, 2020 DWMRC RAI.
1
2.0 BACKGROUND
As stated above, EFRI previously noted potential issues associated with the collection of DO
measurements in the perched aquifer at the Mill. Below is a summary of the potential issues
noted?
Accurate measurement of DO in groundwater collected from perched monitoring wells is
problematic at the Mill due to the low permeability of the formation hosting the perched
groundwater and the consequent low productivity of wells installed to monitor the perched
groundwater.
First, the low rates of perched groundwater flow exacerbate the impact of wells on perched
groundwater oxygen concentrations near the wells. Water flowing through the wells is in contact
with oxygen introduced into the well casings for substantial periods, allowing for substantial
diffusion of oxygen into the groundwater within and near the wells. Transport of oxygen into
perched groundwater is additionally enhanced by barometrically-induced water level fluctuations
within the wells.
Second, most of the wells have screens extending into the vadose zone which allows diffusion of
oxygen into the vadose zone directly above the water table in these wells. This diffusion occurs
in all directions, including upgradient with respect to groundwater flow. This gas-phase
diffusion, which occurs approximately four orders of magnitude more rapidly than aqueous-
phase diffusion, creates a large reservoir of gas-phase oxygen in contact with groundwater near
the wells. Because oxygen from this reservoir is in contact with a relatively large area of
groundwater, diffusive transport to the groundwater is enhanced. In addition, air contains
approximately 30 times more oxygen on a mass per volume basis than groundwater saturated
with oxygen, which increases the mass of oxygen available to be transported to groundwater near
each well. Barometrically-induced water table fluctuations near the wells also enhances transport
of oxygen from this vadose reservoir to the wells.
Third, because of the extremely low productivity of many of the sampled wells, the purging
alone may have a substantial impact on DO. The substantial degree of water level fluctuation
resulting from purging enhances oxygen transport to the groundwater in the immediate vicinity
of the sampled wells. Consequently, wells with lower permeability that have larger fluctuations
as a result of the purging and sampling process will be impacted more than wells having smaller
fluctuations. Furthermore, some wells that purge dry due to low productivity are not sampled
until the following day, allowing more time for oxygen to be transported into the well water.
All these factors are important because they impact oxygen concentrations in groundwater near
the wells prior to sampling. Water at distance from the wells likely contains much lower oxygen
concentrations.
It is important to note that localized elevated DO measurements are noted in other wells in the
vicinity of the Mill. The Ute Mountain Ute ("UMU") wells WM_GWMW_E and
WM_GWMW_W both reported elevated DO results from samples collected in April 2011. The
results were 105.9% saturation and 96.8% saturation respectively (as reported in data tables
provided by UMU Tribe Representative in October 2015).
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3.0 GEOLOGY/HYDROGEOLOGY
The following discussion is based primarily on TITAN (1994) and HydroGeoChem (2018).
The Mill has an average elevation of approximately 5,600 feet above mean sea level (ft. amsl)
and is underlain by unconsolidated alluvium and indurated sedimentary rocks. The indurated
rocks consist primarily of sandstone and shale and are relatively flat lying with dips generally
less than 3°. The alluvial materials consist primarily of aeolian silts and fine-grained aeolian
sands with a thickness varying from a few feet to as much as 25 to 30 feet across the site. The
alluvium is underlain by the Dakota Sandstone and Burro Canyon Formation, and where present,
the Mancos Shale. The Dakota and Burro Canyon are sandstones having a total thickness ranging
from approximately 55 to 140 feet, and, because of their similarity, are typically not
distinguished in lithologic logs at the site. Beneath the Burro Canyon Formation lies the
Morrison Formation, consisting, in descending order, of the Brushy Basin Member, the
Westwater Canyon Member, the Recapture Member, and the Salt Wash Member. The Brushy
Basin and Recapture Members of the Morrison Formation, classified as shales, are very fine-
grained, have a very low permeability, and are considered aquicludes. The Brushy Basin
Member is primarily composed of bentonitic mudstones, siltstones, and claystones. The
Westwater Canyon and Salt Wash Members also have a low average veitical permeability due to
the presence of interbedded shales.
Beneath the Morrison Formation lies the Summerville Formation, an argillaceous sandstone with
interbedded shales, and the Entrada Sandstone. Beneath the Entrada lies the Navajo Sandstone.
The Navajo and Entrada Sandstones constitute the primary aquifer in the vicinity of the site. The
Entrada and Navajo Sandstones are separated from the Burro Canyon Formation by
approximately 1,000 to 1,100 feet of materials having a low average vertical permeability.
Groundwater within this system is under artesian pressure in the vicinity of the site, is of
generally good quality, and is used as a secondary source of water at the site. Although the water
quality and productivity of the Navajo/Entrada aquifer are generally good, the depth
(approximately 1,200 feet below land surface [ft. bls]) makes access difficult.
The shallowest groundwater beneath the site occurs within the Dakota Sandstone and Burro
Canyon Formation. This groundwater is referred to as the 'perched' groundwater and is used on
a limited basis to the north (upgradient) of the site because it is more easily accessible than the
Navajo/Entrada aquifer. Although perched groundwater extends into the overlying Dakota
Sandstone within areas having greater saturated thicknesses, perched groundwater at the site is
hosted primarily by the Burro Canyon Formation, which consists of a relatively hard to hard,
fine- to medium-grained sandstone containing siltstone, shale and conglomeratic materials.
Perched groundwater originates mainly from precipitation and local recharge sources such as
unlined reservoirs (Kirby, 2008) and is supported within the Burro Canyon Formation by the
underlying aquiclude (Brushy Basin Member of the Morrison Formation). Saturated thicknesses
at the site range from less than 1 foot along the downgradient edge of the tailings management
system to approximately 80 feet in upgradient wells located near formerly used unlined wildlife
ponds.
3
Perched water quality is generally poor due to high total dissolved solids ("TDS") in the range of
approximately 1,100 to 7,900 milligrams per liter ("mg/L"), and is used primarily for stock
watering and irrigation. The saturated thickness of the perched water zone generally increases to
the north of the site, increasing the yield of the perched zone to wells installed north of the site.
Perched water flow across the site is generally from northeast to southwest. This general flow
pattern has been consistent based on perched water level data collected beginning with the initial
site investigation described in Dames and Moore (1978). Perched water discharges in seeps and
springs located to the west, southwest, east, and southeast of the site.
The perched zone has generally low permeability. Hydraulic conductivity ranges from
approximately 2 x 10-8 to 0.01 cm/s and has a geometric average (based on slug tests) of
approximately 3 x 10-5 cm/s. The generally low permeability of the perched zone limits well
yields. Although sustainable yields of as much as 4 gallons per minute ("gpm") have been
achieved in site wells penetrating higher transmissivity zones near unlined wildlife ponds, yields
are typically low (<0.5 gpm) due to the generally low permeability of the perched zone. Even site
wells that yielded as much as 4 gpm during the first few months of pumping eventually saw
yields drop to about 1 gpm or less. Total achievable pumping from the 17 wells used to
remediate chloroform and nitrate plumes at the site is less than 7 gpm. In addition, many of the
perched monitoring wells purge dry and take several hours to more than a day to recover
sufficiently for groundwater samples to be collected. During a well redevelopment effort during
2010 and 2011, many of the perched wells went dry during surging and bailing and required
several sessions on subsequent days to remove the proper volumes of water (HGC, 2011).
4.0 EPA-PUBLISHED GUIDANCE FOR LOW—FLOW SAMPLING
EFRI consulted several EPA references regarding micro-purge low-flow sampling as discussed
in Revision 0 of the Low-Flow Sampling Plan and in Section 4.1 below. The DWMRC RAI,
dated May 27, 2020 included an additional reference for low-flow sampling. The DWMRC RAI
requested the inclusion of the provided reference and incorporation of the conclusions regarding
applicability of low-flow techniques presented therein. The additional reference and the
associated conclusions are discussed in Section 4.2 below.
4.1 EPA Guidance for Low-Flow Sampling
EFRI consulted several EPA references regarding micro-purge low-flow sampling including
Low-Flow (Minimal Drawdown) Ground-Water Sampling (Puls and Barcelona, 1996), Ground-
Water Sampling Guidelines for Supeifund and RCRA Project Managers (Yeskis and Zavala,
2002), and EQASOP-GW4, Region 1 Low-Stress (Low-Flow) SOP, Rev 4 (EPA 2017). All of
these reference documents contained limitations on the use of low-flow sampling based on well
screen lengths. Specifically regarding well screens, Puls and Barcelona, 1996 "suggested that
short (e.g., less than 1.6 m) screens be incorporated into the monitoring design where possible so
that comparable results from one device to another might be expected"; Yeskis and Zavala, 2002
states "This method is applicable primarily for short well-screen lengths (less than Sleet (1.6
meters)) to better characterize the vertical distribution of contaminants. This method should not
be used with well-screen lengths greater than 10 feet (3 meters); " EPA Region 1 states "This
procedure is designed for monitoring wells with an inside diameter (1.5 inches or greater) that
4
can accommodate a positive lift pump with a screen length or open interval 10 feet or less and
with a water level above the top of the screen or open interval."
In addition, the general goal of the 2017 EPA Guidance is to achieve minimal disturbance during
purging and sampling. The Guidance therefore calls for minimal drawdown, especially in wells
having screens extending above the static water level. Although not mandatory, EPA
recommends that drawdowns be limited to 0.3 feet. If this condition cannot be met, the EPA
recommends that at least stable drawdowns be achieved. In wells having fully submerged
screens, EPA recommends that water levels do not drop into the screened interval during
purging.
The well screens in the groundwater wells at the Mill are greater than 10 feet and many have
screened intervals that extend above the static water levels. These factors may adversely affect
the data collected for the following reasons:
1) Relatively short screens ensure the collection of low-flow samples that are generally
representative of the relatively small aquifer thicknesses intercepted. However, low-flow
samples collected from long screens may be representative neither of the entire screened
intervals nor of the relatively large aquifer thicknesses intercepted. Conversely, standard
purging and sampling of wells with long screened intervals at the Mill generally ensures
that samples are representative of the entire thickness of aquifer intercepted.
2) Permeabilities of materials penetrated by many of the wells at the Mill are so low that
small or even stable drawdowns may not be achievable during micro-purging; and for
wells having fully submerged screens, preventing water levels from dropping into the
screened intervals may not be possible. The large drawdowns that will unavoidably occur
in many of the wells would essentially defeat the minimal disturbance goal of the
method.
3) Furthermore, the large storage capacity of a long screened interval may prevent
parameter stabilization during micro-purging even if purging of low-permeability wells
continues long enough that unacceptably large drawdowns have not occurred. Under
these conditions, it may not be possible to collect a sample that is both 'undisturbed' and
representative of 'fresh' formation water.
4.2 Other Guidance for Low-Flow Sampling
EFRI reviewed M.J. Barcelona, M.D. Varljen, R.W. Puls and D. Kaminski, Winter 2005, Ground
Water Purging and Sampling Methods: History vs. Hysteria, Ground Water Monitoring &
Remediation 25, no. 1/pp 52-62. This reference states that low-flow sampling techniques should
not be excluded based on well screen lengths alone. Further, this paper indicates that in low
hydraulic conductivity formations, the screen entrance velocities could be kept low despite
significant drawdown as long as draw down stabilized and that the key issue is minimal
drawdown during purging. In addition, the above noted reference noted that the comparison of
data for a well completed in a low hydraulic conductivity formation using both low-flow
sampling and volume base sampling yielded comparable results when the low-flow sampling
5
was completed after stabilization of field parameters. Contrary to the EPA guidance, this
indicates that low-flow sampling can be representative of the entire thickness of the aquifer
intercepted.
It should be noted that EPA has not accepted the conclusions of this paper and still limits low-
flow sampling to wells with a screened interval of 10 feet or less.
4.3 Summary
The references cited in Section 4.1 and 4.2 above provide contradictory guidance for the scope,
application and use of low-flow sampling. Permeabilities of materials penetrated by many of the
wells at the Mill aremay be so low that low-flow samplingand-mftv-Of fftayis not be appropriate
because stable drawdowns cannot be achieved-fer-low-flew-s-amplifig. This study will assess the
use of low-flow sampling at the Mill based on Mill-specific data.
5.0 WELLS INCLUDED IN THIS PLAN
Revision 0 of this Low-Flow Sampling Plan, proposed sampling Ffar upgradient monitoring
wells MW-01, MW-18, and MW 19 will be sampled during this studyonly. While these These
three wells represent a wide range of both hydraulic conductivities and DO results.i, —the
DWMRC RAI requested the inclusion of additional wells where significant oxygenation of
groundwater samples was noted (>10% saturation).
Ten wells will be included in this study. The 10 wells are shown on Table 5.0 and Figure 1.
Table 5.0 provides details regarding each well including the latest DO measurement (range = 1 to
124% saturation), Vadose zone screen interval (range = -37 to 23 feet [with negative values
indicating feet of screen submergence below the water tablel), saturated thickness (range = 8 to
79 feet) and hydraulic conductivity (range = 2.3E-7 to 3.9E-4). The wells are: MW-01, MW-12,
MW-14, MW-18, MW-19, MW-23, MW-27, MW-31, MW-39, and MW-40. These wells were
chosen forbased on the following reasonscriteria:
1) large range in % DO saturation (from <10 percent [2 wellsl to >100% [3 to 4 wells])
2) large areal distribution (within, up-, cross- and down-gradient of the Mill site and tailings
management system)
3) locations close to (3 wells) and more distant from (7 wells) wildlife ponds
4) large range in hydraulic conductivity (from 2e-7 to 4e-4 cm/s)
5) large range in saturated thickness (from < 8 to nearly 80 ft)
6) large range in screen setting (completely submerged fby up to 37 feetl to large extension into
vadose zone [by up to 23 feetl)
7) large range in sampling frequency/year (2 to 12)
8) include wells with and without GWCLs
9) must have dedicated pumps and be able to be sampled using a pump (excludes MW-20, MW-
37, and MW-38)
10) extremely small transmissivity wells excluded (such as MW-20)
6
While DWMRC requested that all wells have DO>10% saturation, two wells with DO
measurements <10% saturation have been included. These wells were included to provide a
complete data set and the data will be used to assess if any noted analytical differences are due to
DO and sample agitation or due to the different sampling methodologies. Including wells from
the full range of DO measurements will more likely allow for a definitive determination of the
causes of any analytical differences if present. Without the low DO data, it is not possible to
completely assess the data and draw definitive conclusions regarding the effects of agitation
versus sampling methodology differences.
Hydraulic testing indicates a three order of magnitude range in hydraulic conductivity:
approximately 7.7 x le cm/s for MW 1; 1.7 x 10 cm/s for MW 19; and 2.9 x 104 cm/s for
MW 18. The value for MW 19 is close to the site geometric average of approximately 3 x 10-5
cm/s. The fourth quarter DO results for MW 01, MW 18, and MW 19 were 12.0%, 1.0% and
103.5% respectively. These wells are sampled-semi-annually-and4e-date-enty-ene-quafter-ef--140
data are available.
In addition, these wells display a relatively large range in saturated thicknesses. Fourth quarter,
2019 saturated thicknesses were approximately 47 feet at MW 01; 67 feet at MW 18; and 79 feet
at MW 19.
6.0 PROCEDURES
To complete this study, EFRI will collect groundwater samples from MW 01, MW 18 and MW
-1-910 wells using the low-flow sampling protocol below followed by routine volume-based,
purging techniques in the DWMRC-approved QAP, in accordance with the schedule set forth in
Section 8.0 below. The low flow samples will be collected the following quarter using the
procedures outlined in Section 6.2 below, in accordance with the schedule in Section 8.0 below.
All samples collected during this study will be submitted to the analytical laboratories currently
used for the monitoring programs at the Mill. Sample containers, shipping and analysis methods
will be consistent with current Mill practices.
The analytical data from both sampling methodologies will be collected and assessed in a final
report as specified in Section 9.0.
6.1 Volume-Based Purging Method
The volume-based, routine purging and sampling procedures detailed in the DWMRC-approved
QAP will be used. No changes are required for this study.
The volume-based purging will commence immediately following the low-flow sampling. The
volume of water purged during the low-flow sampling protocol, can be counted towards the two
casing volume requirement specified in the QAP.
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6.2 Low Flow (Minimal Purge) Sample Method
The U.S. EPA recommends the use of adjustable-rate bladder and electric submersible pumps
during low-flow purging and sampling activities. The following procedures will be completed
using the existing, dedicated, low-flow, bladder pumps currently used at the Mill for routine
sampling. The dedicated pumps will not be moved and the placement within the screened
interval will not be adjusted during this study to minimize disturbances during the study and after
the completion of the study. Previous experience at the Mill indicates that moving or disturbing
well pumps adversely impacts the sample data collected after pump disturbances. Minimizing
disturbance is a primary goal of the low-flow method.
The following procedures will be used for low flow sampling:
6.2.1 Low Flow Well Purging:
1. Prepare sampling equipment including calibration of field meters prior to use.
2. Place water level probe in well and record static water level on the field sheet. Do not
remove the water level probe.
3. Begin purging the well at the minimum pumping rate of 100 milliliters per minute
(mi./min). As soon as the pump tubing has been purged, collect a sample of the standing
(stagnant) water in the well. Label this sample as MW-XXST MMDDYYYY.
3.4. and-sSlowly increase the pumping rate to no more than 500 mL/min. Monitor and record
drawdown in well (if any).
4.-5.Record data on field sampling sheet. If drawdown exceeds 0.3 feet from static, adjust
flow rate until drawdown stabilizes (if possible).
5-.-6.For wells screened below the static water level, if the drawdown does not stabilize at a
pumping rate of 100 mL/min, continue pumping until the drawdown reaches a depth of
two feet above the top of the well screen. Stop pumping and collect a groundwater
sample once the well has recovered sufficiently to collect the appropriate sample volume.
Document the details of purging, including the purge start time, rate, and drawdown on
the field sheet.
7.For wells screened across the static water level, if the drawdown does not stabilize at
100 mL/min, continue pumping. However, do not draw down the water level more than
25 percent of the distance between the static water level and pump intake depth. If the
recharge rate of the well is lower than the minimum pumping rate, then collect samples at
this point even though indicator field parameters have not stabilized. Begin sampling as
soon as the water level has recovered sufficiently to collect the required sample volumes.
Allow the pump to remain undisturbed in the well during this recovery period to
minimize the turbidity. Document the details of purging on the field sheet.
8
7-78.For wells with stable drawdown, start recording field parameters on the field sheet every
3 minutes. Purging should continue at a constant rate until the parameters stabilize.
Stabilization is considered achieved when three sequential measurements are within the
ranges listed below:
• pH ± 0.1 standard units
• Specific Conductance ± 3%
• Temperature ± 3%
• ORP ± 10 millivolts
• Turbidity ± 10% (for values greater than 5 NTUs)
• Dissolved Oxygen ± 10%
6.2.2 Low Flow Well Sampling
1. After specified parameters have stabilized, reduce flow rate on control box to
approximately 100 mL/min
2. Fill necessary sample bottles. Label sample bottles with a unique sample number (e.g.
MW-01LF_01012020), time and date of sampling, the initials of the sampler, and the
requested analysis on the label. Additionally, provide information pertinent to the
preservation materials or chemicals used in the sample. Record comments pertinent to the
color and obvious odor. Record sampling information on field sheet.
3. Fill all sample containers. Immediately seal each sample and place the sample on ice in a
cooler to maintain sample temperature preservation requirements. Fill bottles in the
following order:
a) VOCs, 3 sample containers, 40 ml each;
b) Nutrients (ammonia, nitrate/nitrite as N), 1 sample container, 250 ml;
c) All other non-radiologics (anions, general inorganics, TDS, total cations and total
anions), 2 sample containers, 500 and 250 ml,;
d) Gross alpha, 1 sample container, 250 ml, filtered; and
e) Metals, 1 sample container, 250 ml, filtered.
7.0 QUALITY CONTROL ("QC") SAMPLES
QC samples collected during this study will be the same as those specified in the DWMRC-
approved QAP and will include VOC trip blank and duplicates. Rinsate blanks are not required
as all sampling equipment is dedicated and therefore rinsates are not required.
One of the quarterly duplicate samples collected during the routine volume based, purging and
the associated sampling will be from one of the wells included in this study. A duplicate will-be
eelleeted-frem-the-saffie-well-(if-pessible)-Eitifing-the-lew-fiesamplitig-peftieft-ef-the-stedy, A
9
duplicate sample will be collected from one of the wells included in this study (if possible based
on volume).
8.0 SCHEDULE
Per Part I.E.1.c.2.i of the GWDP specifies a semi annual sampling schedule for MW 01, MW lg
and MW 19. These wells are sampled semi annually during the second and fourth quarters of
each year.
Based on the routine sampling schedule, this study will begin the even numbered quarter (either
second or fourth) after the receipt of the DWMRC approval of this study plan. The volume
based purging and sampling will be conducted during the even numbered quarter per thc routine
schedule specified in the GWDP.
The following quarter (either first or third), the low flow sampling will be conducted as specified
herein.
Since some of the wells included in this study are sampled semi-annually (2nd and 4th quarter),
this study will be conducted the first even numbered quarter after the DWMRC approval of this
plan has been received.
9.0 REPORTS
A final report detailing the sampling conducted, any issues encountered and summarizing the
data will be completed and submitted to DWMRC within 90 days after the end of the final
quarter of sampling.
Field and laboratory data generated as a result of this study will be verified as required by the
DWMRC-approved QAP. Field data will be reviewed to determine if the low-flow sampling
provided data that are usable for the intended purpose. Any issues noted during the low-flow
sampling will be noted, summarized and assessed, including potential effects on analytical data
results and usability. The analytical data from the stagnant sample, the low-flow sample and the
volume-based samples will be compared and assessed using common statistical methods as
appropriate based on the data. Specific details regarding statistical methods will be determined
after the data are received based on what is appropriate for those data. Specific methods will be
discussed in the final report. In addition, the justification for those methods will be included.
The report will include a summary and an assessment of the differences in analytical data as well
as an overall assessment of the low-flow sampling methodology relative to the Mill. The report
will also include a conclusion regarding DO measurements for both sampling methods and
differences in the analytical data, if any, resulting from the two methods.
It is important to note that the low-flow sampling data will not be used for compliance purposes.
The data will not be reported in or included with the quarterly routine groundwater reports. Per
EFRI and DWMRC discussions, any exceedances of GWCLs in the low-flow generated data will
not be used to accelerate sampling frequency in any compliance well. In addition, EFRI will
10
assess any new exceedances in the volume-based analytical data for these wells. If there are
interferences as a result of the back to back purging and sampling events, EFRI will discuss
those with DWMRC prior to implementing accelerated monitorinz. Due to low permeabilities, it
is possible that wells that have not gone dry previously may purge dry during this event that have
net-ciene-dfy-pfevieusly. Wells that do not normally go dry may experience issues with sediment
disturbance that have not been noted previously. Sediment disturbance may change the routine
volume-based results.
11
10.0 REFERENCES
Dames and Moore, 1978. White Mesa Uranium Project, San Juan County, Utah. For Energy
Fuels Nuclear, Inc. January 30, 1978.
HydroGeoChem (HGC), 2011. Redevelopment of Existing Perched Monitoring Wells. White
Mesa Uranium Mill Near Blanding, Utah. September 30, 2011.
HGC, 2018. Hydrogeology of the White Mesa Uranium Mill and Recommended Locations of
New Perched Wells to Monitor Proposed Cells 5A and 5B. July 11, 2018.
Kirby, 2008. Geologic and Hydrologic Characterization of the Dakota-Burro Canyon Aquifer
Near Blanding, San Juan County, Utah. Utah Geological Survey Special Study 123.
M.J. Barcelona, M.D. Varljen, R.W. Puls and D. Kaminski, Winter 2005, Ground Water Purging
and Sampling Methods: History vs. Hysteria, Ground Water Monitoring & Remediation 25, no.
1/pp 52-62
TITAN, 1994. Hydrogeological Evaluation of White Mesa Uranium Mill. Submitted to Energy
Fuels Nuclear.
United States Environmental Protection Agency, 2002, Ground-Water Sampling Guidelines for
Superfund and RCRA Project Managers, Ground Water Forum Issues Paper, Yeskis and Zavala.
United States Environmental Protection Agency, 1996, Ground Water Issue, Low-Flow
(Minimal Drawdown) Ground-Water Sampling Procedures, Puls and Barcelona.
United States Environmental Protection Agency, Region 1. 2017. EQA SOP-GW4 Region 1
Low-Stress (Low-Flow) SOP. Revised September 19, 2017.
12
CLEAN
White Mesa Uranium Mill
Low Flow Sampling Plan
State of Utah
Groundwater Discharge Permit No. UGW370004
Prepared by:
eFENERGY FUELS
Energy Fuels Resources (USA) Inc.
225 Union Boulevard, Suite 600
Lakewood, CO 80228
July 20, 2020
Contents
1.0 INTRODUCTION 1
2.0 BACKGROUND 1
3.0 GEOLOGY/HYDROGEOLOGY 3
4.0 PUBLISHED GUIDANCE FOR LOW-FLOW SAMPLING 4
4.1 EPA Guidance for Low-Flow Sampling 4
4.2 Other Guidance for Low-Flow Sampling 5
4.3 Summary 6
5.0 WELLS INCLUDED IN THIS PLAN 6
6.0 PROCEDURES 7
6.1 Volume-Based Purging Method 7
6.2 Low Flow (Minimal Purge) Sample Method 7
6.2.1 Low Flow Well Purging- 8
6.2.2 Low Flow Well Sampling 9
7.0 QUALITY CONTROL ("QC") SAMPLES 9
8.0 SCHEDULE 9
9.0 REPORTS 9
10.0 REFERENCES 11
1.0 INTRODUCTION
Part I.E.1.d.1, of the State of Utah Groundwater Discharge Permit ("GWDP") dated March 19,
2019, required the addition of Dissolved Oxygen ("DO") to the list of field parameters collected
during groundwater purging. As required by the March 19, 2019 GWDP, Energy Fuels
Resources (USA) Inc. ("EFRI") revised the Quality Assurance Plan ("QAP") to include the
collection of DO during purging. EFRI submitted Revision 7.6 of the QAP for the Division of
Waste Management and Radiation Control ("DWMRC") approval on August 22, 2019.
DWMRC approved Revision 7.6 of the QAP by letter dated September 10, 2019. DO
measurements commenced in the third quarter of 2019. No DO measurements were collected
during the second quarter 2019 groundwater sampling program because the second quarter
sampling program was completed prior to the receipt of the DWMRC's approval of Revision 7.6
of the QAP.
EFRI submitted the third quarter groundwater report on November 13, 2019. By letter dated
January 13, 2020, DWMRC stated that it appeared all applicable requirements of the GWDP
were met, and that the submitted groundwater monitoring data were reliable, and the review was
closed.
The DWMRC letter dated January 13, 2020, noted that several DO monitoring well results were
above 100% oxygen saturation and that the results were greater than DWMRC expected in area
groundwater. DWMRC and EFRI discussed the third quarter results by conference call on
December 11, 2019. Initial evaluation by the EFRI consultant (HydroGeoChem) discussed that
oxygen was likely introduced into the samples due to the low permeability and small, saturated
thickness of the perched aquifer combined with agitation during purging and sampling. Section
2.0 below summarizes the previously submitted EFRI concerns regarding DO measurements and
the limited usability of those data. Per discussion with DWMRC, it was agreed that additional
evaluation would be conducted by EFRI to determine potential effects of the sample
oxygenation, and evaluation of alternate micro-purge/low-flow sample collection to evaluate the
impact of DO in the groundwater samples. EFRI agreed to submit a plan for low flow sampling,
including a planned date for a final report submission to DWMRC for review and approval, on or
before April 9, 2020. The deadline for submission of the plan was extended to May 9, 2020 due
to COVID-19 issues and teleworking requirements. Revision 0 of the Low-Flow Sample Plan
was submitted to DWMRC on May 8, 2020.
DWMRC provided written comments and a Request for Additional Information ("RAI") to the
Low-Flow Sample Plan to EFRI by letter dated May 27, 2020. The RAI requested a revised
Low-Flow Sample Plan be submitted by EFRI on or before July 20, 2020. This plan is being
submitted to address the comments in the May 27, 2020 DWMRC RAI.
2.0 BACKGROUND
As stated above, EFRI previously noted potential issues associated with the collection of DO
measurements in the perched aquifer at the Mill. Below is a summary of the potential issues
noted.
Accurate measurement of DO in groundwater collected from perched monitoring wells is
problematic at the Mill due to the low permeability of the formation hosting the perched
groundwater and the consequent low productivity of wells installed to monitor the perched
groundwater.
First, the low rates of perched groundwater flow exacerbate the impact of wells on perched
groundwater oxygen concentrations near the wells. Water flowing through the wells is in contact
with oxygen introduced into the well casings for substantial periods, allowing for substantial
diffusion of oxygen into the groundwater within and near the wells. Transport of oxygen into
perched groundwater is additionally enhanced by barometrically-induced water level fluctuations
within the wells.
Second, most of the wells have screens extending into the vadose zone which allows diffusion of
oxygen into the vadose zone directly above the water table in these wells. This diffusion occurs
in all directions, including upgradient with respect to groundwater flow. This gas-phase
diffusion, which occurs approximately four orders of magnitude more rapidly than aqueous-
phase diffusion, creates a large reservoir of gas-phase oxygen in contact with groundwater near
the wells. Because oxygen from this reservoir is in contact with a relatively large area of
groundwater, diffusive transport to the groundwater is enhanced. In addition, air contains
approximately 30 times more oxygen on a mass per volume basis than groundwater saturated
with oxygen, which increases the mass of oxygen available to be transported to groundwater near
each well. Barometrically-induced water table fluctuations near the wells also enhances transport
of oxygen from this vadose reservoir to the wells.
Third, because of the extremely low productivity of many of the sampled wells, the purging
alone may have a substantial impact on DO. The substantial degree of water level fluctuation
resulting from purging enhances oxygen transport to the groundwater in the immediate vicinity
of the sampled wells. Consequently, wells with lower permeability that have larger fluctuations
as a result of the purging and sampling process will be impacted more than wells having smaller
fluctuations. Furthermore, some wells that purge dry due to low productivity are not sampled
until the following day, allowing more time for oxygen to be transported into the well water.
All these factors are important because they impact oxygen concentrations in groundwater near
the wells prior to sampling. Water at distance from the wells likely contains much lower oxygen
concentrations.
It is important to note that localized elevated DO measurements are noted in other wells in the
vicinity of the Mill. The Ute Mountain Ute ("UMU") wells WM_GWMW_E and
WM_GWMW_W both reported elevated DO results from samples collected in April 2011. The
results were 105.9% saturation and 96.8% saturation respectively (as reported in data tables
provided by UMU Tribe Representative in October 2015).
3.0 GEOLOGY/HYDROGEOLOGY
The following discussion is based primarily on TITAN (1994) and HydroGeoChem (2018).
The Mill has an average elevation of approximately 5,600 feet above mean sea level (ft. amsl)
and is underlain by unconsolidated alluvium and indurated sedimentary rocks. The indurated
rocks consist primarily of sandstone and shale and are relatively flat lying with dips generally
less than 3°. The alluvial materials consist primarily of aeolian silts and fine-grained aeolian
sands with a thickness varying from a few feet to as much as 25 to 30 feet across the site. The
alluvium is underlain by the Dakota Sandstone and Burro Canyon Formation, and where present,
the Mancos Shale. The Dakota and Burro Canyon are sandstones having a total thickness ranging
from approximately 55 to 140 feet, and, because of their similarity, are typically not
distinguished in lithologic logs at the site. Beneath the Burro Canyon Formation lies the
Morrison Formation, consisting, in descending order, of the Brushy Basin Member, the
Westwater Canyon Member, the Recapture Member, and the Salt Wash Member. The Brushy
Basin and Recapture Members of the Morrison Formation, classified as shales, are very fine-
grained, have a very low permeability, and are considered aquicludes. The Brushy Basin
Member is primarily composed of bentonitic mudstones, siltstones, and claystones. The
Westwater Canyon and Salt Wash Members also have a low average vertical permeability due to
the presence of interbedded shales.
Beneath the Morrison Formation lies the Summerville Formation, an argillaceous sandstone with
interbedded shales, and the Entrada Sandstone. Beneath the Entrada lies the Navajo Sandstone.
The Navajo and Entrada Sandstones constitute the primary aquifer in the vicinity of the site. The
Entrada and Navajo Sandstones are separated from the Burro Canyon Formation by
approximately 1,000 to 1,100 feet of materials having a low average vertical permeability.
Groundwater within this system is under artesian pressure in the vicinity of the site, is of
generally good quality, and is used as a secondary source of water at the site. Although the water
quality and productivity of the Navajo/Entrada aquifer are generally good, the depth
(approximately 1,200 feet below land surface [ft. Ns]) makes access difficult.
The shallowest groundwater beneath the site occurs within the Dakota Sandstone and Burro
Canyon Formation. This groundwater is referred to as the 'perched' groundwater and is used on
a limited basis to the north (upgradient) of the site because it is more easily accessible than the
Navajo/Entrada aquifer. Although perched groundwater extends into the overlying Dakota
Sandstone within areas having greater saturated thicknesses, perched groundwater at the site is
hosted primarily by the Burro Canyon Formation, which consists of a relatively hard to hard,
fine- to medium-grained sandstone containing siltstone, shale and conglomeratic materials.
Perched groundwater originates mainly from precipitation and local recharge sources such as
unlined reservoirs (Kirby, 2008) and is supported within the Burro Canyon Formation by the
underlying aquiclude (Brushy Basin Member of the Morrison Formation). Saturated thicknesses
at the site range from less than 1 foot along the downgradient edge of the tailings management
system to approximately 80 feet in upgradient wells located near formerly used unlined wildlife
ponds.
Perched water quality is generally poor due to high total dissolved solids ("TDS") in the range of
approximately 1,100 to 7,900 milligrams per liter ("mg/L"), and is used primarily for stock
watering and irrigation. The saturated thickness of the perched water zone generally increases to
the north of the site, increasing the yield of the perched zone to wells installed north of the site.
Perched water flow across the site is generally from northeast to southwest. This general flow
pattern has been consistent based on perched water level data collected beginning with the initial
site investigation described in Dames and Moore (1978). Perched water discharges in seeps and
springs located to the west, southwest, east, and southeast of the site.
The perched zone has generally low permeability. Hydraulic conductivity ranges from
approximately 2 x 10-8 to 0.01 cm/s and has a geometric average (based on slug tests) of
approximately 3 x 10-5 cm/s. The generally low permeability of the perched zone limits well
yields. Although sustainable yields of as much as 4 gallons per minute ("gpm") have been
achieved in site wells penetrating higher transmissivity zones near unlined wildlife ponds, yields
are typically low (<0.5 gpm) due to the generally low permeability of the perched zone. Even site
wells that yielded as much as 4 gpm during the first few months of pumping eventually saw
yields drop to about 1 gpm or less. Total achievable pumping from the 17 wells used to
remediate chloroform and nitrate plumes at the site is less than 7 gpm. In addition, many of the
perched monitoring wells purge dry and take several hours to more than a day to recover
sufficiently for groundwater samples to be collected. During a well redevelopment effort during
2010 and 2011, many of the perched wells went dry during surging and bailing and required
several sessions on subsequent days to remove the proper volumes of water (HGC, 2011).
4.0 PUBLISHED GUIDANCE FOR LOW-FLOW SAMPLING
EFRI consulted several EPA references regarding micro-purge low-flow sampling as discussed
in Revision 0 of the Low-Flow Sampling Plan and in Section 4.1 below. The DWMRC RAI,
dated May 27, 2020 included an additional reference for low-flow sampling. The DWMRC RAI
requested the inclusion of the provided reference and incorporation of the conclusions regarding
applicability of low-flow techniques presented therein. The additional reference and the
associated conclusions are discussed in Section 4.2 below.
4.1 EPA Guidance for Low-Flow Sampling
EFRI consulted several EPA references regarding micro-purge low-flow sampling including
Low-Flow (Minimal Drawdown) Ground-Water Sampling (Puls and Barcelona, 1996), Ground-
Water Sampling Guidelines for Supofund and RCRA Project Managers (Yeskis and Zavala,
2002), and EQASOP-GW4, Region 1 Low-Stress (Low-Flow) SOP, Rev 4 (EPA 2017). All of
these reference documents contained limitations on the use of low-flow sampling based on well
screen lengths. Specifically regarding well screens, Puls and Barcelona, 1996 "suggested that
short (e.g., less than 1.6 m) screens be incorporated into the monitoring design where possible so
that comparable results from one device to another might be expected"; Yeskis and Zavala, 2002
states "This method is applicable primarily for short well-screen lengths (less than 5 feet (1.6
meters)) to better characterize the vertical distribution of contaminants. This method should not
be used with well-screen lengths greater than 10 feet (3 meters); " EPA Region 1 states "This
procedure is designed for monitoring wells with an inside diameter (1.5 inches or greater) that
can accommodate a positive lift pump with a screen length or open interval 10 feet or less and
with a water level above the top of the screen or open interval."
In addition, the general goal of the 2017 EPA Guidance is to achieve minimal disturbance during
purging and sampling. The Guidance therefore calls for minimal drawdown, especially in wells
having screens extending above the static water level. Although not mandatory, EPA
recommends that drawdowns be limited to 0.3 feet. If this condition cannot be met, the EPA
recommends that at least stable drawdowns be achieved. In wells having fully submerged
screens, EPA recommends that water levels do not drop into the screened interval during
purging.
The well screens in the groundwater wells at the Mill are greater than 10 feet and many have
screened intervals that extend above the static water levels. These factors may adversely affect
the data collected for the following reasons:
1) Relatively short screens ensure the collection of low-flow samples that are generally
representative of the relatively small aquifer thicknesses intercepted. However, low-flow
samples collected from long screens may be representative neither of the entire screened
intervals nor of the relatively large aquifer thicknesses intercepted. Conversely, standard
purging and sampling of wells with long screened intervals at the Mill generally ensures
that samples are representative of the entire thickness of aquifer intercepted.
2) Permeabilities of materials penetrated by many of the wells at the Mill are so low that
small or even stable drawdowns may not be achievable during micro-purging; and for
wells having fully submerged screens, preventing water levels from dropping into the
screened intervals may not be possible. The large drawdowns that will unavoidably occur
in many of the wells would essentially defeat the minimal disturbance goal of the
method.
3) Furthermore, the large storage capacity of a long screened interval may prevent
parameter stabilization during micro-purging even if purging of low-permeability wells
continues long enough that unacceptably large drawdowns have occurred. Under these
conditions, it may not be possible to collect a sample that is both 'undisturbed' and
representative of 'fresh' formation water.
4.2 Other Guidance for Low-Flow Sampling
EFRI reviewed M.J. Barcelona, M.D. Varljen, R.W. Puls and D. Kaminski, Winter 2005, Ground
Water Purging and Sampling Methods: History vs. Hysteria, Ground Water Monitoring &
Remediation 25, no. 1/pp 52-62. This reference states that low-flow sampling techniques should
not be excluded based on well screen lengths alone. Further, this paper indicates that in low
hydraulic conductivity formations, the screen entrance velocities could be kept low despite
significant drawdown as long as draw down stabilized and that the key issue is minimal
drawdown during purging. In addition, the above noted reference noted that the comparison of
data for a well completed in a low hydraulic conductivity formation using both low-flow
sampling and volume base sampling yielded comparable results when the low-flow sampling
was completed after stabilization of field parameters. Contrary to the EPA guidance, this
indicates that low-flow sampling can be representative of the entire thickness of the aquifer
intercepted.
It should be noted that EPA has not accepted the conclusions of this paper and still limits low-
flow sampling to wells with a screened interval of 10 feet or less.
4.3 Summary
The references cited in Section 4.1 and 4.2 above provide contradictory guidance for the scope,
application and use of low-flow sampling. Permeabilities of materials penetrated by many of the
wells at the Mill may be so low that low-flow sampling is not appropriate because stable
drawdowns cannot be achieved. This study will assess the use of low-flow sampling at the Mill
based on Mill-specific data.
5.0 WELLS INCLUDED IN THIS PLAN
Revision 0 of this Low-Flow Sampling Plan, proposed sampling far upgradient monitoring wells
MW-01, MW-18, and MW-19 only. While these three wells represent a wide range of both
hydraulic conductivities and DO results, the DWMRC RAI requested the inclusion of additional
wells where significant oxygenation of groundwater samples was noted (>10% saturation).
Ten wells will be included in this study. The 10 wells are shown on Table 5.0 and Figure 1.
Table 5.0 provides details regarding each well including the latest DO measurement (range = 1 to
124% saturation), Vadose zone screen interval (range = -37 to 23 feet [with negative values
indicating feet of screen submergence below the water table]), saturated thickness (range = 8 to
79 feet) and hydraulic conductivity (range = 2.3E-7 to 3.9E-4). The wells are: MW-01, MW-12,
MW-14, MW-18, MW-19, MW-23, MW-27, MW-31, MW-39, and MW-40. These wells were
chosen based on the following criteria:
1) large range in % DO saturation (from <10 percent [2 wells] to >100% [3 to 4 wells])
2) large areal distribution (within, up-, cross- and down-gradient of the Mill site and tailings
management system)
3) locations close to (3 wells) and more distant from (7 wells) wildlife ponds
4) large range in hydraulic conductivity (from 2e-7 to 4e-4 cm/s)
5) large range in saturated thickness (from < 8 to nearly 80 ft)
6) large range in screen setting (completely submerged [by up to 37 feet] to large extension into
vadose zone [by up to 23 feet])
7) large range in sampling frequency/year (2 to 12)
8) include wells with and without GWCLs
9) must have dedicated pumps and be able to be sampled using a pump (excludes MW-20, MW-
37, and MW-38)
10) extremely small transmissivity wells excluded (such as MW-20)
While DWMRC requested that all wells have DO> 10% saturation, two wells with DO
measurements <10% saturation have been included. These wells were included to provide a
complete data set and the data will be used to assess if any noted analytical differences are due to
DO and sample agitation or due to the different sampling methodologies. Including wells from
the full range of DO measurements will more likely allow for a definitive determination of the
causes of any analytical differences if present. Without the low DO data, it is not possible to
completely assess the data and draw definitive conclusions regarding the effects of agitation
versus sampling methodology differences.
6.0 PROCEDURES
To complete this study, EFRI will collect groundwater samples from 1 0 wells using the low-flow
sampling protocol below followed by routine volume-based, purging techniques in the
DWMRC-approved QAP.
All samples collected during this study will be submitted to the analytical laboratories currently
used for the monitoring programs at the Mill. Sample containers, shipping and analysis methods
will be consistent with current Mill practices.
The analytical data from both sampling methodologies will be collected and assessed in a final
report as specified in Section 9.0.
6. 1 Volume-Based Purging Method
The volume-based, routine purging and sampling procedures detailed in the DWMRC-approved
QAP will be used. No changes are required for this study.
The volume-based purging will commence immediately following the low-flow sampling. The
volume of water purged during the low-flow sampling protocol, can be counted towards the two
casing volume requirement specified in the QAP.
6.2 Low Flow (Minimal Purge) Sample Method
The U.S. EPA recommends the use of adjustable-rate bladder and electric submersible pumps
during low-flow purging and sampling activities. The following procedures will be completed
using the existing, dedicated, low-flow, bladder pumps currently used at the Mill for routine
sampling. The dedicated pumps will not be moved and the placement within the screened
interval will not be adjusted during this study to minimize disturbances during the study and after
the completion of the study. Previous experience at the Mill indicates that moving or disturbing
well pumps adversely impacts the sample data collected after pump disturbances. Minimizing
disturbance is a primary goal of the low-flow method.
The following procedures will be used for low flow sampling:
6.2.1 Low Flow Well Purging.-
1. Prepare sampling equipment including calibration of field meters prior to use.
2. Place water level probe in well and record static water level on the field sheet. Do not
remove the water level probe.
3. Begin purging the well at the minimum pumping rate of 100 milliliters per minute
(mL/min). As soon as the pump tubing has been purged, collect a sample of the standing
(stagnant) water in the well. Label this sample as MW-XXST_MMDDYYYY.
4. Slowly increase the pumping rate to no more than 500 mL/min. Monitor and record
drawdown in well (if any).
5. Record data on field sampling sheet. If drawdown exceeds 0.3 feet from static, adjust
flow rate until drawdown stabilizes (if possible).
6. For wells screened below the static water level, if the drawdown does not stabilize at a
pumping rate of 100 mL/min, continue pumping until the drawdown reaches a depth of
two feet above the top of the well screen. Stop pumping and collect a groundwater
sample once the well has recovered sufficiently to collect the appropriate sample volume.
Document the details of purging, including the purge start time, rate, and drawdown on
the field sheet.
7. For wells screened across the static water level, if the drawdown does not stabilize at
100 mL/min, continue pumping. However, do not draw down the water level more than
25 percent of the distance between the static water level and pump intake depth. If the
recharge rate of the well is lower than the minimum pumping rate, then collect samples at
this point even though indicator field parameters have not stabilized. Begin sampling as
soon as the water level has recovered sufficiently to collect the required sample volumes.
Allow the pump to remain undisturbed in the well during this recovery period to
minimize the turbidity. Document the details of purging on the field sheet.
8. For wells with stable drawdown, start recording field parameters on the field sheet every
3 minutes. Purging should continue at a constant rate until the parameters stabilize.
Stabilization is considered achieved when three sequential measurements are within the
ranges listed below:
• pH ± 0.1 standard units
• Specific Conductance ± 3%
• Temperature ± 3%
• ORP ± 10 millivolts
• Turbidity ± 10% (for values greater than 5 NTUs)
• Dissolved Oxygen ± 10%
6.2.2 Low Flow Well Sampling
1. After specified parameters have stabilized, reduce flow rate on control box to
approximately 100 mL/min.
2. Fill necessary sample bottles. Label sample bottles with a unique sample number (e.g.
MW-01LF_01012020), time and date of sampling, the initials of the sampler, and the
requested analysis on the label. Additionally, provide information pertinent to the
preservation materials or chemicals used in the sample. Record comments pertinent to the
color and obvious odor. Record sampling information on field sheet.
3. Fill all sample containers. Immediately seal each sample and place the sample on ice in a
cooler to maintain sample temperature preservation requirements. Fill bottles in the
following order:
a) VOCs, 3 sample containers, 40 ml each;
b) Nutrients (ammonia, nitrate/nitrite as N), 1 sample container, 250 ml;
c) All other non-radiologics (anions, general inorganics, TDS, total cations and total
anions), 2 sample containers, 500 and 250 ml,;
d) Gross alpha, 1 sample container, 250 ml, filtered; and
e) Metals, 1 sample container, 250 ml, filtered.
7.0 QUALITY CONTROL ("QC") SAMPLES
QC samples collected during this study will be the same as those specified in the DWMRC-
approved QAP and will include VOC trip blank and duplicates. Rinsate blanks are not required
as all sampling equipment is dedicated and therefore rinsates are not required.
A duplicate sample will be collected from one of the wells included in this study (if possible
based on volume).
8.0 SCHEDULE
Since some of the wells included in this study are sampled semi-annually (2nd and 4th quarter),
this study will be conducted the first even numbered quarter after the DWMRC approval of this
plan has been received.
9.0 REPORTS
A final report detailing the sampling conducted, any issues encountered and summarizing the
data will be completed and submitted to DWMRC within 90 days after the end of the quarter.
Field and laboratory data generated as a result of this study will be verified as required by the
DWMRC-approved QAP. Field data will be reviewed to determine if the low-flow sampling
provided data that are usable for the intended purpose. Any issues noted during the low-flow
sampling will be noted, summarized and assessed, including potential effects on analytical data
results and usability. The analytical data from the stagnant sample, the low-flow sample and the
volume-based samples will be compared and assessed using common statistical methods as
appropriate based on the data. Specific details regarding statistical methods will be determined
after the data are received based on what is appropriate for those data. Specific methods will be
discussed in the final report. In addition, the justification for those methods will be included.
The report will include a summary and an assessment of the differences in analytical data as well
as an overall assessment of the low-flow sampling methodology relative to the Mill. The report
will also include a conclusion regarding DO measurements for both sampling methods and
differences in the analytical data, if any, resulting from the two methods.
It is important to note that the low-flow sampling data will not be used for compliance purposes.
The data will not be reported in or included with the quarterly routine groundwater reports. Per
EFRI and DWMRC discussions, any exceedances of GWCLs in the low-flow generated data will
not be used to accelerate sampling frequency in any compliance well. In addition, EFRI will
assess any new exceedances in the volume-based analytical data for these wells. If there are
interferences as a result of the back to back purging and sampling events, EFRI will discuss
those with DWMRC prior to implementing accelerated monitoring. Due to low permeabilities, it
is possible that wells that have not gone dry previously may purge dry during this event. Wells
that do not normally go dry may experience issues with sediment disturbance that have not been
noted previously. Sediment disturbance may change the routine volume-based results.
10.0 REFERENCES
Dames and Moore, 1978. White Mesa Uranium Project, San Juan County, Utah. For Energy
Fuels Nuclear, Inc. January 30, 1978.
HydroGeoChem (HGC), 2011. Redevelopment of Existing Perched Monitoring Wells. White
Mesa Uranium Mill Near Blanding, Utah. September 30, 2011.
HGC, 2018. Hydrogeology of the White Mesa Uranium Mill and Recommended Locations of
New Perched Wells to Monitor Proposed Cells 5A and 5B. July 11, 2018.
Kirby, 2008. Geologic and Hydrologic Characterization of the Dakota-Burro Canyon Aquifer
Near Blanding, San Juan County, Utah. Utah Geological Survey Special Study 123.
M.J. Barcelona, M.D. Varljen, R.W. Puls and D. Kaminski, Winter 2005, Ground Water Purging
and Sampling Methods: History vs. Hysteria, Ground Water Monitoring & Remediation 25, no.
1/pp 52-62
TITAN, 1994. Hydrogeological Evaluation of White Mesa Uranium Mill. Submitted to Energy
Fuels Nuclear.
United States Environmental Protection Agency, 2002, Ground-Water Sampling Guidelines for
Superfund and RCRA Project Managers, Ground Water Forum Issues Paper, Yeskis and Zavala.
United States Environmental Protection Agency, 1996, Ground Water Issue, Low-Flow
(Minimal Drawdown) Ground-Water Sampling Procedures, Puls and Barcelona.
United States Environmental Protection Agency, Region 1. 2017. EQA SOP-GW4 Region 1
Low-Stress (Low-Flow) SOP. Revised September 19, 2017.
FIGURE

TWN-11

TWN-07
TWN-02 MW-27

wildlife pond

DR-14 DR-15
TWN-12 TWN-19
TWN-16
TWN-15 TWN-17
TWN-14
o rwrv-lo
o TWN-09
TWN-01 TW4-2t PI 3A
• • MW-24 MW-02
DR-05 DR-06 DR-07 \ MW-35.
MW-360
•
4 24 • TWTIN
4-227
3vv:-
2:9
6:-7
-
46z
,rw
-
4:
4
:
36:;
1
-
10:7
4:4
-538

E J AN
1
:
4-
4
1
-
3
12
TW4-02
TW4-P28 Yit32
•TWI070 RA,"44:0480TW4-36 Mt31 row-32 TW4-01 TW4-04 TW4-41
Twt24r4.064-341(N7:$72il-v1v44.31
• TW*-260 (-) OTW4-30 MW-25 11N4-4e TW4-29- 0TW4-35
11/44,424 TWC-21.
wildlife pond
DR-1 • INV 1 DR-12 DR-13 PIEZ-05
• MW-21
Cell 4.F.
MW-28
•O. MW-38
19 DR-20
DR-23
EXPLANATION
perched monitoring well proposed
for low-flow sampling showing 19 latest DO in % saturation
TW4-42
(:)
temporary perched monitoring well
installed April 2019
TW4-40 perched chloroform pumping well
installed February 2018
T111/4-19
(I) perched chloroform or
nitrate purnping well COkk:A1,.,SPRNGS
MW-38
<>" perched monitoring well installed
February 2018
MW-5
• perched monitoring well
TW4-12
0 temporary perched monitoring well
TWN-7 temporary perched nitrate monitoring
• well
PIEZ-1 perched piezometer
RUIN SPRING
(!) seep or spring
WHITE MESA SITE PLAN SHOWING LOCATIONS OF HYDRO WELLS FOR LOW-FLOW SAMPLING TEST GEO AND LATEST DISSOLVED OXYGEN (DO) CHEM, INC. APPROVED DATE REFERENCE FIGURE H:/718000/71802/DOissue/
LowFlowPlan/LowFlowWells.srf 1
TABLE
Table 5.0
Non-Pumping Wells Proposed to Test Low-Flow Purging and Sampling
Well
UTME
(meters)
UTMN
(meters)
Latest Dissolved
Oxygen (DO)
(% saturation)
Feet Vadose
Screen14
Feet
Saturated
Thickness3
Hydraulic
Conductivity
(cm/s)4
GWDP-Specified
Number of
Sampling Events
(per year)
Current
Number of
Sampling
Events (per
year)
MW-01 632049 4156277 12.8 -29.2 47.2 7.70E-07 2 2
MW-12 631228 4154733 52.3 23.2 7.8 6.61E-05 2 4
MW-14 631683 4154278 13 12.1 18.9 3.88E-04 4 12
MW-18 632293 4156108 1 -32.2 66.9 2.90E-04 2 2
MW-19 632687 4155914 124 -36.7 79.2 1.70E-05 2 2
MW-23 631056 4154775 51 4.1 13.7 2.30E-07 2 2
MW-27 632059 4155532 96.5 13.6 33.4 8.20E-05 2 4
MW-31 632096 4154832 110 -1.3 58.3 7.10E-05 4 12
MW-39 632221 4153396 7.9 0.8 33.7 1.76E-05 4 4
MW-40 632566 4153638 107.6 8.2 38.8 1.26E-04 4 4
range NA NA 1 to 124 -37 to 23 8 to 79 2.3e-7 to 3.9e-4 2 to 4 2 to 12
Notes:
negative vadose screen length = depth of submergence qf top qf screen
2'3 calculated from Q4 2019 data
4 cm/s = centimeters per second
Criteria for selection of wells: 1) large range in % DO saturation (from <10 percent [2 wells] to >100% [3 to 4 wells])
2) large areal distribution (within, up-, cross- and down-gradient of the millsite and tailings management system)
3) locations close to (3 wells) and more distant from (7 wells) wildlife ponds
4) large range in hydraulic conductivity (from 2e-7 to 4e-4 cm/s)
5) large range in saturated thickness (from < 8 to nearly 80 ft)
6) large range in screen setting (completely submerged [by up to 37 feet] to large extension into vadose zone [by up to 23 feet])
7) large range in sampling frequency/year (2 to 12)
8) include wells with and without GWCL's
9) must have dedicated pumps
10) extremely small transmissivity wells excluded (such as MW-20)