DRC-2013-002141 - 0901a0688037678e

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State of Utah
GARY R HERBERT
Governor
GREG BELL
Lieutenant Governor
Department of
Environmental Quality
Amanda Smith
Executive Director
DIVISION OF RADIATION CONTROL
Rusty Lundberg
Director
DRC-2013-
MEMORANDUM
TO: File
THROUGH: Phil Goble, Compliance Section Manager
FROM: Tom Rushing P.G.
April 23, 2013 DATE:
SUBJECT DRC Staff Review of Energy Fuels Resources (USA) Inc. October 10,2012 Source
Assessment Report White Mesa Uranium Mill and associated pH assessment
documents (dated November 9, 2012 pH Report and December 7, 2012 Pyrite
Investigation Report).
Summary
This memo is to provide Utah Division of Radiation Control ("DRC") staff findings and
recommended actions regarding review of three documents submitted by Energy Fuels Resources
(USA) Inc. ("EFR"). The documents are regarding ground water monitoring parameters in out of
compliance status at the White Mesa Uranium Mill under Utah Ground Water Discharge Permit,
Permit No. UGW370004 (Permit), and include:
1. The EFR, October 10, 2012, Source Assessment Report White Mesa Uranium Mill,
prepared by Intera Geosciences & Engineering ("Intera"),
2. The EFR, November 9, 2012, pH Report White Mesa Uranium Mill, prepared by Intera,
and,
3. The EFR, December 7, 2012, Investigation of Pyrite in the Perched Zone White Mesa
Uranium Mill Site, prepared by Hydro Geo Chem, Inc. ("HGC").
Background
The documented studies, findings and actions in the three reviewed documents are under purview
of conditions and timelines outlined in the Utah Department of Environmental Quality Stipulated
Consent Agreement Docket No. UGWI2-03 ('SCA UGW12-03"). UGW12-03 additionally
provides for associated stipulated penalties for non-conformance with the study objectives and
timelines outlined therein.
195 North 1950 West • Salt Lake City, UT
Mailing Address P O Box 144850 • Salt Lake City, UT 84114-4850
Telephone [phone] • Fax [phone] • T D D [phone]
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EFR Source Assessment Reports
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The three listed reports provide justification for the findings and proposals related to
out-of-compliance ("OOC") parameters at certain monitoring wells and for certain parameters at
the White Mesa Uranium Mill ("Mill") which were originally identified and enforced through
DRC Notice of Violation and Order Docket No UGW11-02.
Findings and proposals regarding EFR proposed modified GWCLs or removal of GWCLs at
certain monitoring wells, pursuant to the three documents, are justified by study evidence showing
that the OOC wells are due to groundwater background influences in the shallow Burro Canyon
Formation Aquifer and not due to discharges from the Mill. The three listed reports are related
and are required in order to provide adequate support that the OOC status is due to background.
The boxes below summarize the objective of the three listed reports as follows:
October 10, 2012 EFR Source Assessment Report - Provides explanation and
source assessment study of OOC exceedances except for pH. Provides
statistical analysis of data and includes graphs and tables of analysis. Proposes
modified Groundwater Compliance Limits for OOC Parameters, except pH.
November 9, 2012 pH Report - Provides source assessment study for monitoring
wells in OOC for pH. Proposes modified pH Groundwater Compliance Limits
for pH for all MW series monitoring wells based on field measurements.
December 7,2012 EFR Pyrite Investigation Report - Provides findings of a
study to support the regional geochemical process explaining decreasing pH
trends at monitoring wells. Study analyzes quantities of iron pyrite (from
monitoring well cores and cuttings) and models dissolution in the Burro Canyon
Formation.
Discussion of a Previous University of Utah Study to Determine if the Mill Tailings Cells
were Leaking
During July 17, 2007 through July 26,2007, the University of Utah conducted field work for a
study to evaluate whether increasing trace metal (e.g. uranium) concentration in ground water at
several of the White Mesa Uranium Mill were being caused by leakage from the on-site tailings
cells. The results of the study were published in the May 18, 2008 "Evaluation of Solute Sources
at Uranium Processing Site" (U of U Study) and were used to justify modifications to the facility
groundwater water permit in January 2010 which included approval of Energy Fuels Resources
Background Ground Water Quality Reports dated October 2007 and April 30, 2008 and
subsequent approval of revised Ground Water Compliance Limits.
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The Study findings were related to: 1. Local groundwater flow, 2. The chemical composition of
the groundwater, 3. Isotopic composition of the groundwater, 4. Evaluation of noble gas
composition of the groundwater, and 5. Age of the groundwater at the Mill monitoring wells
(Study wells).
The Study concluded that excess total uranium concentrations in downgradient monitoring wells
MW-3, MW-14, MW-15 and MW-17 are likely the product of changing geochemical conditions
induced by artificial recharge from the wildlife ponds and not due to tailings cell leakage.
These conclusions were largely based on isotopic analysis results of groundwater samples
collected by the University of Utah. Specifically, the study evaluated ratios of Tritium,
Deuterium, Oxygen-18 and Sulfur-34 in ground water.
Part 3.3 of the EFR October 10, 2012 Source Assessment Report additionally summarizes the
Study and cites the Study in support of the determination that current OOC wells/parameters are
due to background influences and are not due to tailings cell leakage.
Discussion of Tailings Solution Groundwater Indicator Parameters
The November 9, 2012 pH Report Section 2.5 discusses indicator parameters which would be
detected in ground water in the event of discharge from the Mill tailings impoundments. Section
2.5 discusses that such discharge would be indicated by rising concentrations of chloride, sulfate,
fluoride and uranium as these potential contaminants are abundant in the tailings wastewater and
are relatively mobile and conservative in groundwater systems.
Per the November 9, 2012 pH report, the indicator parameters are ordered as the best indicators as
follows; chloride, then fluoride, then sulfate, then uranium. It is noted that, in terms of metals and
radionuclides, uranium is the most mobile and best indicator parameter.
1. Chloride ~ Chloride is listed as the best indicator of tailings solution release since the
retardation Factor (Rf) equals 1 (transported in saturated zone at the same velocity as the
groundwater). High concentrations of chloride are present in the tailings solution with an
average concentration of approximately 20,752 mg/L using 2012 data from Cell 1, Cell 2
Slimes Drain, Cell 3 and Cells 4A and 4B. Per the pH Report, this concentration is
"sufficient to guarantee" that chloride would be measurable in groundwater before any
substantial volume had entered the system.
2. Fluoride - Fluoride shares similar chemical properties and transport velocity as chloride.
However it is noted that fluoride is in the tailings impoundment solution at a lower
concentration than chloride, approximately 486 mg/L based on 2012 concentrations
measured in Cell 1, Cell 2 Slimes Drain, Cell 3 and Cells 4A and 4B. Additionally, apatite
acts as a solubility control and can reduce fluoride concentrations along a ground water
flow path (higher Rf). The pH Report notes that fluoride is secondary to chloride as an
indicator of discharge of tailings solution.
3. Sulfate - Sulfate is present in ambient groundwater at proportionally higher concentrations
than chloride. Calcium sulfate minerals are more soluble than chloride minerals which
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EFR Source Assessment Reports
DRC Review Memo
limit the amount of sulfate that can remain dissolved and subsequently retards sulfate
concentrations along a flow path. The tailings cells contain an average concentration of
approximately 96,040 mg/L calculated from 2012 samples of Cell 1, Cell 2, Slimes Drain,
Cell 3 and Cells 4A and 4B. Given these high concentrations in the tailings solution,
sulfate is still a good indicator parameter of discharge.
4. Uranium - Uranium is the most mobile of trace (metal) elements. Uranium is more mobile
in ground water with low pH values and typically the retardation coefficient is
significantly higher at pH values above the 3 to 4.5 range.
DRC Review - October 10,2012 EFR Source Assessment Report
Summary:
The October 10,2012 Source Assessment Report evaluates wells/parameters currently in OOC
status which were cited in a DRC Notice of Violation Docket Number UGW11-02 ("NOV"),
dated May 9, 2011 for failure on the part of EFR to conduct a source assessment study per
provisions of the Permit. Subsequently, the SCA UGW12-03 was issued to agree upon, and
approve, details required to be included in the study.
EFR, therefore, provided the October 10, 2012 Source Assessment Study to address the agreed
upon studies for the wells/parameters in OOC, which were cited in the NOV as follows:
Parameter g|gmtorinM(gll Number
Cadmium MW-24
Manganese MW-11
Selenium MW-12
MW-30
MW-3
MW-3A
Thallium MW-18
MW-24
Uranium MW-26
MW-5
MW-25
TDS MW-18
MW-27
MW-31
Sulfate
Fluoride
MW-31
MW-3A
MW-3
Per DRC review of the October 10, 2012 Source Assessment Report it appears that the agreed
upon studies outlined in SCA UGW12-03 were included. The Report evaluates the well
parameters based on their status as either: 1. Parameters in wells with previously identified rising
trends, 2. Parameters in pumping wells, 3. Parameters impacted by site-wide pH trends, 4.
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EFR Source Assessment Reports
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Parameters in newly installed wells with interim GWCL's, and 5. Other parameters. The Report
additionally evaluates whether background influences are the cause of the exceedances and
recommends revised GWCL's based on the Director approved flowsheet associated with the
Background Groundwater Monitoring Report (Intera 2007).
DRC noted that per Part 3.2 of the October 10, 2012 Source Report, EFR states that the Director
approved statistical flowsheet does not allow the revised GWCL's to be set high enough for
anticipated "near future" trends which EFR anticipates will cause the well/parameter to enter a
renewed out-of-compliance status for: 1. Uranium in well MW-5, 2. Manganese in Well MW-11,
and, 3. TDS in Well MW-31. EFR therefore proposes that DRC and EFR "enter into discussions
to determine if there are approaches that will allow the GWCL's to be set in a manner that better
reflects changing background conditions" at those wells/parameters.
As discussed below, EFR additionally proposes to remove GWCL's at four monitoring wells, well
numbers MW-1, MW-18, MW-19, and MW-26, based on their location or use as a pumping well
for chloroform plume remediation. DRC notes that EFR did calculate potential proposed
modifications for the TDS and Thallium GWCLs at well MW-18 and for Uranium at well MW-26
(current wells parameters in OOC) in the event that removing the GWCLs at those wells is not
approved by the Director.
EFR Request to Remove GWCL's at Monitoring Wells MW-1, MW-18, MW-1% and MW-26:
Per Part 3.2 of the October 10, 2012 Report EFR proposes that the GWCL's in upgradient
monitoring wells MW-1, MW-18 and MW-19 be eliminated, as well as the GWCL's in pumping
well MW-26. EFR proposes the removal of GWCL's from upgradient wells MW-1, MW-18 and
MW-19 since they are far upgradient from the Mill and cannot be impacted by Mill activities, and
from pumping well MW-26 on the basis that the well is being manipulated, and the impact on
ground water quality "cannot be predicted with enough certainty to establish a compliance
standard' in the Permit. Additionally, per Part 3.2 of the October 10, 2012 Report EFR "proposes
to continue monitoring those wells at their normal, unaccelerated frequency for informational
purposes only, and to help define background conditions at the site."
EFR did calculate revised GWCL's for monitoring wells MW-26 and MW-18 for the OOC
parameters, based on the SCA requirements, and included those revisions with the October 10,
2012 Source Assessment Report. Additionally, EFR calculated revised GWCL's for pH as
included in the November 9, 2012 pH Report for the four wells requested to have the GWCLs
removed.
DRC agrees with the justifications provided by EFR, that far-upgradient wells are not likely to be
impacted by current Mill activities based on review of kriged water level maps included with the
Mill Quarterly Ground Water Reports. Specifically, per DRC review of the water level elevations,
the elevations at monitoring wells MW-1, MW-18 and MW-19 are higher than water elevations in
the Burro Canyon Aquifer beneath all of the Mill tailings cells. Additionally, those monitoring
wells are located north and northeast of the tailings cells, local groundwater flow is to the south-
southwest. If future groundwater gradients change such that there is reasonable evidence to
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EFR Source Assessment Reports
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suggest that any of the upgradient wells MW-1, MW-18 or MW-19 may be impacted by tailings
cell discharge or other Mill related activities, then the Director will re-institute GWCL's in the
Permit at any or all of the monitoring wells. Continued semi-annual (baseline) monitoring for all
contaminants listed in Table 2 of the current Permit (Current - DRC 8/24/2012) will be required to
continue for continued assessment of background groundwater quality at monitoring wells MW-1,
MW-18 and MW-19.
Specifically, DRC justifications to allow removal of GWCL's at wells MW-1, MW-18 and MW-
19 are as follows:
1. Per DRC review of water elevation maps and expected groundwater flow directions, wells
MW-1, MW-18, and MW-19 are hydraulically upgradient from the Mill,
2. Groundwater monitoring for all currently monitored parameters listed on Table 2 of the
permit will continue at baseline monitoring frequencies and will be submitted with the
Mill Quarterly Ground Water Monitoring Reports,
3. Continuation of GWCL's at upgradient monitoring wells may result in unnecessary
enforcement action and source assessment.
DRC also agrees that the MW-26 pumping well monitoring data is not predictable and does not
allow establishment of dependable GWCLs, however, DRC notes that actions related to the
chloroform plume pumping remediation project have not been formalized and that the removal of
GWCL's prior to emplacement of performance guidelines, penalties, and regulatory conditions for
pumping well MW-26 is premature. Therefore, removal of GWCL's at monitoring well MW-26
is not approved. EFR may re-apply for removal of GWCL's at well MW-26 after approval and
execution of a corrective action plan ("CAP") for the chloroform contaminant plume.
Specifically, DRC denial of the request to remove GWCL's at pumping well MW-26 is as
follows:
1. Well MW-26 has not been formalized as a pumping well under the chloroform ground
water remediation project and specific pump performance requirements, including
continued maintenance of a capture zone on the eastern margins of tailings cells 2 and 3,
are not under regulatory enforcement requirements,
2. Well MW-26 is the current compliance monitoring detection point, and regulatory tool to
require source assessment, for potential tailing solution release on the eastern margins of
tailings cells 2 and 3.
3. EFR may submit a separate proposal to remove Permit GWCL's at pumping well MW-26
after execution of a Stipulated Consent Agreement for the chloroform plume remediation
program.
OOC Wells/Parameters with Previously Identified Rising Trends:
EFR evaluation of previous rising trends applies to the following wells/parameters:
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Manganese in well MW-11
Selenium in wells MW-12 and MW-3
Thallium in well MW-18
Uranium in well MW-26
The current data for these wells/parameters were compared with historic data used for analysis of
the background reports to determine if significant statistical changes were occurring. Based on
the EFR analysis as well as geochemical evaluation and supported by the findings of the
University of Utah Study, EFR concludes that these exceedances are in conformance with
identified historical trends and proposes revised GWCL's for the wells/parameters.
OOC Wells/Parameters Pumping Wells:
EFR evaluation of pumping wells applies to uranium in well MW-26. The October 10,2012
Source Assessment Report additionally notes that results of the Mann-Kendall trend test
concluded that the uranium data and pH data is not showing a statistically significant increasing
trend (only the chloride indicator parameter shows a significant trend at the well). EFR
additionally notes that pH at the well is not showing an increasing trend. EFR additionally notes
that the variability of concentrations for all parameters at well MW-26 was noted by DRC in the
September 2009 Statement of Basis for the Groundwater Permit.
OOC Wells/Parameters pH Impacts:
EFR evaluation of constituents potentially impacted by site-wide decreasing pH trends applies to
the wells/parameters listed below. Also note that the pH trends and potential geochemical
processes are outlined in the EFR November 9, 2012 pH Report.
Cadmium in well MW-24
Manganese in well MW-11
Selenium in Wells MW-3, MW-3A, MW-12 and MW-30
Thallium in wells MW-18 and MW-24
Uranium in wells MW-5, MW-25 and MW-26
Per the EFR conclusions for these OOC wells/parameters, including evaluation of the indicator
parameters (discussed above) and discussion of expected concentrations (dissolution and mobility)
of the OOC parameters due to decreases in pH, EFEL concludes that the exceedances for the
wells/parameters listed above are due to the site-wide pH decreases and is therefore attributed to
natural background concentrations in the aquifer.
EFR proposes revised GWCL's for these wells/parameters as discussed below. As discussed
above, EFR projects that the proposed revised GWCL's for uranium in well MW-5 and
Manganese in well MW-11 will be exceeded in the near future (due to ongoing projected
decreases in pH due to potential pyrite dissolution in the aquifer). EFR recommends additional
discussion between DRC and EFR to determine if alternate methods of GWCL calculation may be
utilized for these wells. DRC staff will recommend that the EFR proposed modified GWCLs for
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EFR Source Assessment Reports
DRC Review Memo
wells MW-5 and MW-11 be included in the Permit renewal in the interim, until an alternate
method to set GWCLs can be agreed upon.
OOC Wells/Parameters New Wells - Interim GWCL's:
EFR evaluation of constituents in newly installed wells with interim GWCL's applies to
Manganese, Selenium, Thallium, Uranium and Gross Alpha in well MW-35
EFR notes that a background report is currently being prepared for the setting of GWCL's at this
well (being prepared concurrently with the Source Assessment Report). Therefore, proposed
GWCL's are not included in the October 10, 2012 Source Assessment Report for well GW-35 but
will be based on the comprehensive background determination for the well for all constituents in
Table 2 of the Permit.
OOC Wells/Parameters Other Constituents and Wells:
EFR evaluation of other constituents and wells applies to the wells/parameters listed below:
TDS in wells MW-18, MW-27 and MW-31
Sulfate in wells MW-31 and MW-3 A
Fluoride in well MW-3
Per EFR source assessment study of these wells/parameters the following conclusions were made
Well Parameter Summary of Findings
MW-3 Fluoride Far downgradient, no significant increasing trend in chloride,
consistent with background conditions
MW-3A Sulfate No consistent increasing trend in sulfate or any other indicator
parameters, far downgradient, consistent with background
conditions
MW-18 TDS Far upgradient, consistent with background conditions
MW-27 TDS Located at the margin of the nitrate/chloride plume, mass
balance determine unfeasible tailings leakage, University of
Utah Study supports natural background
MW-31 TDS Located at the margin of the nitrate/chloride plume, mass
balance determine unfeasible tailings leakage, University of
Utah Study supports natural background
MW-31 Sulfate Located at the margin of the nitrate/chloride plume, mass
balance determine unfeasible tailings leakage, University of
Utah Study supports natural background
EFR Study concerning the source of the OOC at these wells included geochemical analysis of
indicator parameters, mass balance determination done with the nitrate contamination
investigation (dated December 30, 2009) which calculated an approximate volume of tailings
solution discharge needed to produce the observed groundwater concentrations, potential time
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EFR Source Assessment Reports
DRC Review Memo
needed to transport contamination to the monitoring wells, and conclusions of the University of
Utah Study (isotopic evidence) that tailings cell leakage has not been detected at studied site
monitoring wells. Additionally, EFR concludes that increases in TDS at monitoring wells MW-27
and MW-31 are related to the nitrate/chloride plume.
Therefore, based on the EFR conclusions the OOC wells/parameters for "other constituents" are
attributable to geochemical processes in the aquifer or in the case of TDS at wells MW-27 and
MW-31, are related to the nitrate/chloride plume which is being addressed under a separate action.
Statistical Methods: f
Appendix B-l of the October 10, 2012 Source Assessment Report includes a spreadsheet which
summarizes the statistical analysis for each well/parameter evaluated. Included are summaries
for:
Data population
% Non-detected values
Mean Calculation
Standard Deviation Calculation
Shapiro-Wilk Test for Normality
Least Squares Regression Analysis - Where appropriate
Mann-Kendal Trend Analysis - Where appropriate
Summaries where trends were identified - Based on recent data
Data which had an insensitive detection limit, was a zero value or was determined to be an
extreme outlier was culled from the data set. Additionally, no duplicate values (e.g. blind
duplicates) were included in the evaluated data sets. Appendix B-5 summarizes the data culled.
Data distribution for wells/parameters with consecutive exceedances is represented by box plots
(Appendix B-6) to justify outliers (extreme values) in the data sets and support subsequent
evaluation to determine whether there is a normal distribution of data. The plots and culled data
are in conformance with Director approved statistical process flowchart.
In all cases of data evaluation the data population consisted of at least 8 data points (after culling
outliers) in conformance with the approved flowchart. The generation of the data populations
appears appropriate for the evaluated wells/parameters based on DRC review.
The Appendix B-l flow chart additionally includes a summary of % non-detected values in the
culled data population used for statistical evaluation. Based on the approved flow chart the
remaining evaluation is based on the number of non-detects in the data population. None of the
data sets used during the statistical evaluation for each well/parameter exceeded 50%, therefore
EFR was required to test for normality for all data populations using the Shaprio-Wilk Test (log-
normal or normal).
Per DRC review it was verified that the Shapiro-Wilk Test was performed for each well/parameter
and that in cases where the data was not determined to be log-normal or normally distributed, a
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EFR Source Assessment Reports
DRC Review Memo
Mann-Kendall Trend Analysis was performed. In cases where the data was determined to be
normally distributed, least squares trend analysis was performed.
The table below summarizes each well/parameter including the EFR proposed GWCL revision
and the DRC review regarding whether the calculated proposed revision is in compliance with the
Director approved flowchart method. Note that a modified approach to setting the GWCL (other
than calculation of Mean + 2a can be used in any well where a significant upward trend is
identified with DRC Director approval.
Table of EFR Proposed Revised GWCL's:
Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
MW-3 Fluoride Far
Down-
gradient
0.68 Not
identified in
Background
Report but
no increase
in chloride
Travel time
from cell 4B
over 2,000
years
No chloride
trend
UofU 0-18
no
evaporated
stable
isotope
Previously
Identified
Trends
Decreasing
pH Trend
Fraction
GWCL
Yes
l%Non-
Detects,
Calculate
Mean + 2a,
however,
significant
increasing
trend detected
MW-3 Selenium Far
Down-
gradient
37 52.8
Above
State Std.
U of U Study
trace metals
and depleted
Oxygen-18
Decreasing
pH Trend
HHV Yes
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DRC Review Memo
Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
MW-3A Selenium Far
Down-
gradient
89 109.58 No Indicator
Parameters
Show
Increasing
Trend
Decreasing
pH Trend
Mean + 2o Yes
MW-3A Sulfate Far
Down-
gradient
3640 3949.27 Chloride,
Fluoride and
Uranium do
not show
significant
increasing
trend
2,000 ft
downgradien
t form
tajlings cells
Mean + 2a Yes
MW-5 Uranium Down-
gradient
Cell 3
South
Embankm
ent
7.5 7.5
Same as
current
EFR
proposes
further
study for
uranium
to
determine
variability
Chloride and
Sulfate not
significantly
increasing
After outliers
removed
uranium data
showed a
decreasing
trend
U of U trace
metals
concentratio
ns
Decreasing
pH Trend
Fraction
GWCL
Proposed
GWCL is the
same as the
current
GWCL in the
Groundwater
Permit.
MW-11 Manganes
e
Down-
gradient
Cell 3
South
131.29 164.67
EFR
proposes
further
Background
Report Same
Behavior
No Chloride,
Mean + 2a Yes
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Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
Embankm
ent
study for
manganes
e to
determine
variability
Fluoride or
Uranium
Trend
UofUold
water
terrigenic
helium
Previously
Identified
Trends
Decreasing
pH Trend
MW-12 Selenium Down-
gradient
Cell 3
South
Embankm
ent
25 39 Background
Report Same
Behavior
also Uranium
and Sulfate
Increasing no
other
indicators
increasing
Previously
Identified
Trends
Decreasing
pH Trend
HHV Yes,
36% Non-
Detects,
Calculate
Mean + 2a,
However,
significant
increasing
trend detected
MW-18 TDS Up-
gradient
3198.7
7
3280,
EFR
Request to
Remove
Upgradient
from Mill
Site
Upward
trends for
sulfate and
uranium
identified
during
background
report
U of U study
HHV Yes,
0%Non-
Detects,
Calculate
Mean + 2a,
However,
significant
increasing
trend detected
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DRC Review Memo
Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
for trace
metals
concentratio
ns
Nitrate and
Chloride
Plume
MW-18 Thallium Up-
gradient
1.95 4.00,
Above
State Std.
EFR
Request to
Remove
Located far
upgradient of
Mill
Activities
U of U study
trace metal
concentratio
ns similar to
historically-
observed
concentratio
ns
Possibly
impacted by
rising water
levels due to
Wildlife
Ponds
Previously
Identified
Trends
Decreasing
pH Trend
HHV Yes,
0%Non-
Detects,
Calculate
Mean + 2a,
However,
significant
increasing
trend detected
?HHV 3.91
MW-24 Cadmium Down-
gradient
Cell 1
2.5 4.28 Early non1
detects due
to RL of 0.5
uL
No
increasing
trends for
chloride,
HHV Yes, 44%
Non-Detects,
Calculate
Mean + 2a,
However
significant
increasing
trend detected
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EFR Source Assessment Reports
DRC Review Memo
Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
sulfate,
fluoride or
uranium
Downward
pH Trend
Decreasing
pH Trend
MW-24 Thallium Down-
gradient
Cell 1
1.57 Early non-
detect values
at high RL
Indicator
Parameters
Chloride,
Fluoride,
Sulfate,
Uranium do
not show
significant
increasing
trends.
Decreasing
pH Trend
HHV Yes
MW-25 Uranium Lateral
Cell 3
East
6.5 7.25 Chloride,
Fluoride and
Sulfate do
not exhibit
statistically
significant
increasing
trends
Decreasing
pH Trend
Mean + 2a Yes
MW-26 Uranium Lateral
Cell 2
East
Pumping
Well
41.8 119,
EFR
Request to
Remove
Chloroform
Plume
Pumping
Well
Previously
Identified
HHV Yes,
0% Non-
Detects,
Calculate
Mean + 2a,
however,
Page 15 of 41
EFR Source Assessment Reports
DRC Review Memo
Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
Trends significant
increasing
trend detected
MW-27 TDS Upgradien
t Cell 1
North
Embankm
ent
1,075 1185.72 New
identified
trend
Chloride and
Sulfate Show
Increasing
Trends
Fluoride and
Uranium
Downward
Trends
Mass balance
for Nitrate
Contaminati
on Study
Eliminated
Tailings Cell
U of U Study
Nitrate and
Chloride
Plume
Mean + 2a Yes
MW-30 Selenium Down-
gradient
Cell 2
34 47.2 Located at
Margin of
nitrate/chlori
de plume -
increasing
chloride
concentratio
ns
U of U Study
trace metal
concentratio
ns and
depleted
Oxygen-18
HHV Yes,
0% Non-
Detects,
Calculate
Mean + 2a,
however,
significant
increasing
trend detected
Page 16 of 41
EFR Source Assessment Reports
DRC Review Memo
Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
Decreasing
pH Trend
MW-31 Sulfate Down-
gradient
Cell 2
532 552
EFR
proposes
further
study for
uranium
to
determine
variability
Located on
the
downgradien
t margin of
the nitrate
and chloride
plume
TDS and
Chloride also
showing
significant
increasing
trends
Fluoride
showing
significant
decreasing
trend
Uranium
trending
downward
Sulfate in
MW-31 are
among the
lowest at the
site
Highest
result is 7
percent
higher than
the average
well
concentratio
n (517 mg/L)
HHV Yes,
0% Non-
Detects,
Calculate
Mean + 2a,
however,
significant
increasing
trend detected
?HHV41.9
MW-31 TDS Down-
gradient
1,320 1410.57 New
identified
Mean + 2a Yes
Page 17 of 41
EFR Source Assessment Reports
DRC Review Memo
Well
Number
Parameter Location Current
GWCL
(mg/L)
EFR
Proposed
GWCL
Revision
(mg/L)
EFR
Background
Rationale
EFR
Method to
Determine
GWCL
DRC Finding
- Is Proposed
GWCL in
Conformance
with the
Statistical
Flow Chart?
Cell 2 trend
Chloride and
Sulfate Show
Increasing
Trends
Fluoride and
Uranium
Downward
Trends
Mass balance
for Nitrate
Contaminati
on Study
Eliminated
Tailings Cell
U of U Study
Nitrate and
Chloride
Plume
October 10, 2012 EFR Source Assessment Report DRC Conclusions:
Based on DRC review of the October 10, 2012 EFR Source Assessment Report, DRC concurs
with justification for determination that OOC parameters are caused by natural background
fluctuation and proposed GWCL modification request, it is recommended that the following
modified GWCL's be included in the upcoming groundwater permit renewal.
Monitoring Well Mo.
MW-3
MW-3
MW-3A
MW-3A
MW-12
MW-24
MW-24
MW-25
Parameter
Fluoride
Selenium
Selenium
Sulfate
Selenium
Cadmium
Thallium
Uranium
Current GWCL
(mg/L)
0.68
37
89
3640
25
2.5
6.5
Modified GWCL
(mg/L)
2
52.8
109.58
3949.27
39
4.28
1.57
7.25
Page 18 of 41
EFR Source Assessment Reports
DRC Review Memo
MW-26 Uranium 4L8 119
MW-27 TDS 1075 1185.72
MW-30 Selenium 34 47.2
MW-31 TDS 1320 1410.57
Based on DRC Review of the October 10, 2012 Source Assessment Report it is recommended that
GWCL's be removed from the permit for the following 3 monitoring wells.
'^^^^g.:;,l - , Justification for Removal of GWCL's , - g:
MW-1 Located upgradient from uranium mill facility and tailings disposal
MW-18 Located upgradient from uranium mill facility and tailings disposal
MW-19 Located upgradient from uranium mill facility and tailings disposal
Based on DRC Review of the October 10, 2012 Source Assessment Report it is recommended that
DRC and EFR meet to discuss alternate study and/or statistical measures to calculate GWCL's for
Uranium at monitoring well MW-5, Manganese at monitoring well MW-11 and TDS at
monitoring well MW-31 to account for EFR anticipated future increased concentrations above the
proposed GWCL's. DRC notes that the current proposed GWCL for monitoring well MW-5 is
the same as the current GWCL included in the groundwater permit. DRC recommends that the
following proposed GWCL's be modified in the permit in the interim, until an alternate method to
calculating the GWCL can be agreed upon.
•Monitoring Well No.
MW-11
MW-31
Parameter
Manganese
Sulfate
> Current GWCL
' (mg/L)
131.29
532
Modified GWCL
(mg/L)
164.67
552
November 9,2012 pH Report
Summary:
Study assesses the source of decreasing pH to determine whether it is from natural background or
tailings solution discharge.
Achieves studies through:
1. Geochemical analysis of indicator parameters (chloride, sulfate, fluoride and uranium)
2. Review of the potential for tailings cell discharge including mass balance calculation
3. Whether or not trends in other parameters (including other OOC parameters) is due to
decreases in pH at MW series monitoring wells
The study aimed to provide a site-wide analysis of pH trends and includes an analysis of trends at
all monitoring wells onsite, including chloroform (TW-4) and nitrate (TWN) ground water
sampling. The Report includes statistical evaluation and histograms of pH at those wells. Of the
Page 19 of 41
EFR Source Assessment Reports
DRC Review Memo
twenty-five chloroform monitoring wells, all but two indicated a downward pH trend. Of the
nineteen nitrate monitoring wells, twelve showed a general upward pH trend, four showed a
general downward trend and three showed a flat trend.
DRC notes that the nitrate monitoring wells are primarily located upgradient of the uranium mill
site. Additionally, the nitrate monitoring wells were installed in 2009 and there are fewer pH
measurements at these wells than at other monitoring wells at the site. EFR additionally notes that
the data at these wells is not showing a significant trend in either direction and that the wells may
have been installed after trending occurred.
The study was conducted in largely the same manner as the October 10, 2012 Source assessment
report, using geochemical and supporting evidence to show that the pH decreases are due to
natural occurrences and not to tailings cell leakage. In cases where applicable, the November 9,
2012 report uses indicator parameters to show that pH declines are not due to cell leakage. Per the
discussion of indicator parameters above, chloride is considered the best indicator (most
conservative) to determine tailings cell leakage. Per the November 9,2012 Report, if the pH
decreases were due to tailing cell leakage then, given the chloride concentrations in the tailing cell
solution and the non-reactive (Rf = 1) nature of chloride, an increasing trend in chloride would
precede a declining pH trend. DRC concurs with this factor in determination of the potential
tailings cell source. Where chloride concentration trends existed in monitoring wells at the site,
Intera utilized geochemical information for other indicator parameters (e.g. sulfate). It is also
noted that decreasing pH trends are observed in monitoring well hydraulically upgradient and far
downgradient from the mill facility (appears to be site-wide process).
Additionally, the November 9, 2012 pH Report cites the University of Utah isotopic study, that
previously identified trends in the background report, and site hydrogeological reports to justify
that the pH declines are due to natural background. Based on review of the pH study, DRC staff
concur that the decreasing pH trends appear to be due to variations of natural background,
potentially/possibly caused by the dissolution of pyrite in the formation as discussed in DRC
review comments related to the December 7, 2012 EFR Pyrite Investigation Report in the section
below. EFR maintains that areas of the Burro Canyon Aquifer are being oxygenated due to
infiltration from the wildlife ponds and/or pumping of the monitoring wells.
Statistical and Geochemical Evaluation:
The Report includes a summary of proposed revised GWCL's for all MW monitoring well (not
limited to pH in wells with current OOC status) since the current pH background limits were
based on laboratory and not field pH values.
Statistical evaluation is conducted according to the Director approved flowchart (Intera 2007) and
includes the following analysis techniques:
1. Box plot analysis to identify outliers
2. Histograms using the Shapiro-Wilk test to determine if the data are normally or log-
normally distributed,
Page 20 of 41
EFR Source Assessment Reports
DRC Review Memo
3. Mann-Kendall test if the data is not normally or log-normally distributed to determine data
trends
4. Linear regression charts of field pH data to determine normality of the data (since there are
no non-detects in the data sets) based on the square of the correlation coefficient (R) and
statistical significance (p-level)
Statistical analysis is also included for pH trends in all chloroform and nitrate wells.
DRC staff verified that the statistical process appears to be in conformance with the Director
approved flowchart.
Table 3 of the November 9, 2012 pH Report provides a spreadsheet which includes:
1. A list of monitoring wells evaluated (excluding chloroform and nitrate monitoring wells)
2. Data population (N) used for the statistical evaluation
3. A list of out-of-compliance status for other parameters at the monitoring well
4. A list of indicator parameters showing significant increasing trends at the monitoring well
5. Results of the Shapiro-Wilk test for normality
6. Results of the Least Squares Regression Trend Test
7. Results of the Mann-Kendall Trend Analysis (where applicable per flow chart)
8. Mean and standard deviation calculation results
9. Minimum and Maximum measured pH values for each monitoring well evaluated
10. Mean - 2a calculation
11. Current and proposed GWCL's
12. A list of the rationale for the proposed GWCL
Appendices to the November 9, 2012 pH report include plots and tables regarding statistical
analysis and extreme outliers for: 1. Statistical Analysis of Field pH in Groundwater Monitoring
Wells (Appendix A), 2. Exploratory Linear Regressions for Field pH in Groundwater Monitoring
Wells (Appendix B), 3. Groundwater Elevation and Field pH in all Wells (Appendix C), 4.
Indicator Parameters Analysis for Wells with Out-of-Compliance Status or Statistically
Significant Decreasing Trends in Field pH (Appendix D), 5. Statistical Analysis of Field pH in
Chloroform Wells (Appendix E), 6. Statistical Analysis of Field pH in Nitrate Wells (Appendix
F), and 7. Electronic Input and Output Files.
*
Groundwater Elevation and Field pH Plots of Data
The November 9, 2012 pH Report notes that increasing water levels are a possible explanation for
decreasing pH at the site as discussed above. Per the plots included in Appendix C, which include
plots of water level fluctuations with time and field pH over time, all MW and TW4 plots show
rising water levels correlated with decreasing pH, with the exception of two plots (wells TW4-12
and TWN-2). Issues related to oxygenation of the aquifer and dissolution of pyrite is discussed in
more detail in the DRC review comments related to the December 7, 2012 Pyrite investigation
report in sections below.
Page 21 of 41
EFR Source Assessment Reports
DRC Review Memo
Data Omitted Prior to Statistical Analysis
Appendix A-6 of the November 9, 2012 lists data which was omitted prior to statistical analysis.
The values which were excluded are considered to be extreme outliers in the data set. Per DRC
review of the omitted data, DRC staff concurs that the omitted data appears to include only
extreme values.
Per Section 2.3 of the November 9,2012 pH Report, it is also noted that Intera performed data
exploration using different time period to determine if certain monitoring wells show past or
present declining trends for pH. Intera used two categories for the data exploration: 1.
Measurements collected prior to 2005, and 2. Measurements collected from 2005 through the
second half of 2012.
Data was similarly culled for pH data sets related to the TWN and TW4 statistical analysis.
EFR Recommendations:
The November 9, 2012 pH Report recommends elimination of all GWCL's for chloroform
pumping well MW-26 and up gradient monitoring wells MW-1, MW-18, and MW-19. Per
discussion in the DRC review comments related to the October 10, 2012 Source Assessment
Report above, the same request was made regarding the removal of all GWCL's for these wells in
that report. Since the request was addressed during that review, additional actions regarding the
pH Report request are not included.
EFR Proposed Modified GWCL fsforpH
Table - Proposed GWCL's for pH
Well
Number
•s m- km Location
-.§3 -
Previous111
pH
GWCL
(sift)''' s
EFR * =
Proposed «
GWCL
Revision1*
(S.U.)
EFR ****
Background
Rationale
EFR ?v *;
Method .to
Determine
^GWfeL* >•
DRC Finding
^Is.Prpposed
GWCL in
Conformance
with the
Statistical
KIOMF^^-
Chart?*
MW-1 Upgradient 6.77-8.5 6.68-8.5,
EFR
Request
to
Remove
Not in OOC Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
Page 22 of 41
EFR Source Assessment Reports
DRC Review Memo
MW-2 Lateral
Gradient W.
Cell 2
6.5-8.5 6.72-8.5 Not in OOC Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-3 Far
Downgradient
6.5-8.5 6.04-8.5 No Chloride
Trend
Travel Time to
MW-3
No Upward
Trends in
Indicator
Parameters
U of U Study
Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-3A Far
Downgradient
6.5-8.5 5.84-8.5 No increasing
trends in
indicator
parameters
Travel time to
MW-3A
U of U Study
Mean - 2a Down Trend
Mean - 2a
Consistent
With Flow
Chart
MW-5 Downgradient
Cell 3 South
Embankment
6.5-8.5 7.04-8.5 Chloride and
Sulfate are not
increasing
Chloride shows
a decreasing
trend
Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-11 Downgradient
Cell 3 South
Embankment
6.5-8.5 6.25-8.5 Chloride
decreasing
trend
Sulfate
Increasing,
Sulfate and
Chloride
should rise
together
U or U study -
terrigenic
behavior
indicates old
ground water
LHV Sig. Down
Trend
Modified
Approach
LHV
Consistent
With Flow
Chart
Page 23 of 41
EFR Source Assessment Reports
DRC Review Memo
MW-12 Downgradient
Cell 3 South
Embankment
6.5-8.5 5.86-8.5 Decreasing
chloride trend
No change in
behavior since
existing wells
background
report
LHV NS Down
Trend
Not
Consistent
With Flow
Chart,
Should be
Mean - 2a
MW-14 Downgradient
Cell 4A
6.5-8.5 5.42-8.5 No change in
behavior since
existing wells
background
report
No indicators
except
Uranium show
increasing
trend.
LHV NS Down
Trend
Not
Consistent
With Flow
Chart,
Should be
Mean - 2a
MW-15 Downgradient
Cell 4A
6.62-8.5 5.88-8.5 Not in OOC
but showing
significant
decreasing
trend
Chloride and
Fluoride show
decreasing
trends
Sulfate
Increasing
trend in
Uranium
identified with
background
report
LHV NS Down
Trend
Not
Consistent
With Flow
Chart,
Should be
Mean - 2a
MW-17 Downgradient
500' Cell 4A
Southeast
Corner
6.4-8.5 6.27-8.5 Not in OOC Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
Page 24 of 41
EFR Source Assessment Reports
DRC Review Memo
MW-18 Upgradient 6.25-8.5 5.87-8.5,
EFR
Request
to
Remove
Mean - 2a Sig. Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-19 Upgradient 6.78-8.5 6.27-8.5,
EFR
Request
to
Remove
Not in OOC Mean - 2o Sig. Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-23 Downgradient
Cell 3
6.5-8.5 5.97-8.5 No change in
behavior since
existing wells
background
report
Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-24 Downgradient
Cell 1
6.5-8.5 5.55-8.5 No increasing
trends in any
indicator
parameter
including
chloride
Mean - 2a Sig. Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-25 Lateral Cell 3
East
6.5-8.5 5.77-8.5 No increasing
trend in
chloride
LHV Sig. Down
Trend
Modified
Approach
LHV
Consistent
With Flow
Chart
MW-26 Lateral Cell 2
East
Pumping
Well
6.74-8.5 5.61-8.5,
EFR
Request
to
Remove
Pumping well
No decreasing
trend in pH
LHV None
Not
Consistent
With Flow
Chart,
Should be
Mean - 2a
Page 25 of 41 ;
EFR Source Assessment Reports
DRC Review Memo
MW-27 Upgradient
Cell 1 North
Embankment
6.5-8.5 6.47-8.5 Located at the
margin of the
nitrate/chloride
plume
Mass balance
of potential
tailings
solution
discharge is
unfeasible
Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-28 Downgradient
Celll
6.1-8.5 5.58-8.5 Potentially
influenced by
the
nitrate/chloride
plume
No increasing
trends in any
other indicator
parameters
except
chloride.
Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-29 Downgradient
Cell2
6.46-8.5 5.94-8.5 Chloride,
fluoride and
sulfate are
exhibiting
downward
trends
Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-30 Downgradient
Cell 2
6.5-8.5 6.47-8.5 Located at the
margin of the
nitrate/chloride
plume
Nitrate/chloride
ratio in
groundwater is
not indicative
of tailings
solution
discharge
Mean - 2a Sig. Down
Trend
Mean - 2a
Consistent
With Flow
Chart
Page 26 of 41
EFR Source Assessment Reports
DRC Review Memo
MW-31 Downgradient
Cell 2
6.5-8.5 6.57-8.5 Located at the
downgradient
margin of the
nitrate/chloride
plume
Chloride/nitrate
ratio of
groundwater is
not indicative
of tailings
solution
discharge
U of U Study
discounted
tailings
discharge as a
source at this
well
Mean - 2a NS Down
Trend
Mean - 2a
Consistent
With Flow
Chart
MW-32 Lateral Cell 2
East
Embankment
6.4-8.5 5.31-8.5 No increasing
trends in
indicator
parameters
LHV Sig. Down
Trend
Modified
Approach
LHV
Consistent
With Flow
Chart
Conclusions
Based on DRC review of the November 9, 2012 EFR pH Report, concurrence with justification
for determination that OOC pH measurements are caused by natural background fluctuation and
proposed GWCL modification request, it is recommended that the following modified GWCL's
be included in the upcoming groundwater permit renewal.
Monitoring Well No. Parameter Current GWCL Modified GWCL v -\
(S.U.) £1
MW-2
MW-3
MW-3A
MW-5
MW-11
MW-17
MW-23
MW-24
^H
pH
pH
pH
PH
pH
pH
pH
6.5-8.5
6.5-.5
6.5-8.5
6.5-8.5
6.5-8.5
6.4- 8.5
6.5- 8.5
6.5-8.5
6.72-8.5
6.04-8.5
5.84-8.5
7.04-8.5
6.25-8.5
6.27-8.5
5.97-8.5
5.55-8.5
Page 27 of 41
EFR Source Assessment Reports
DRC Review Memo
MW-25
MW-27
MW-28
MW-29
MW-30
MW-31
MW-32
pH
pH
pH
pH
pH
pH
j)H
6.5-8.5
6.5-8.5
6.1-8.5
6.46-8.5
6.5-8.5
6.5-8.5
6.4-8.5
5.77-8.5
6.47-8.5
5.58-8.5
5.94-8.5
6.47-8.5
6.57-8.5
5.31-8.5
*Note that several of the EFR modified GWCL requests are not related to wells in OOC status.
As discussed above EFR notes in the November 9, 2012 pH report that "all current GWCL's for
pH at the site were incorrectly set, based on laboratory pH"
Per DRC review, the proposed modified GWCL's for pH at the following three wells were not
calculated in conformance with the Director approved statistical flowchart. The corrected
GWCL's following the flowchart are shown below:
Monitoring Welf^ Parameter *#-^Curfett GWCL Modified GWCL
'-;»#f* (S.U.) *
Corrected
GWCL (S.U.) ^
MW-12 pH 6.5 - 8.5 5.86-8.5 6.21-8.5
MW-14 6.5-8.5 5.42-8.5 5.93-8.5
MW-15 6.62 - 8.5 5.88-8.5 6.34-8.5
MW-26 6.74 - 8.5 5.61-8.5 5.92 - 8.5
December 7,2012 Pyrite Investigation Report
Summary:
Evaluations of field data and other indicator parameters identified and discussed in the November
9, 2012 pH report is dependent on an evaluation of the local Burro Canyon formation mineralogy
and deposition characterization to verify that concentrations of iron pyrite within the Burro
Canyon aquifer are high enough to substantiate the systemic pH decreases due to oxygenation of
the aquifer.
Sample Collection, Screening and Analysis:
DRC staff attended the HGC core/cuttings sample collection for the pyrite investigation on
August 24, 2012. A copy of the review memo which summarizes the inspection is attached to this
memo (Attachment 1).
Screening Level Calculations:
HGC states in the December 7, 2012 Pyrite Report that monitoring wells MW-3 A, MW-24 and
MW-27 are considered representative of the site since they are located far downgradient,
immediately downgradient and immediately upgradient of the tailings cells. HGC therefore
Page 28 of 41
EFR Source Assessment Reports
DRC Review Memo
performs calculations and modeling based on the core/cuttings results from these three monitoring
wells. HGC notes that monitoring well MW-3A "can be considered a worst case example
because of the relatively low detected pyrite concentrations in this well boring, a change in sulfate
concentrations (hundreds of milligrams per liter) which implies a relatively large mass ofpyrite
has been oxidized, and because of the presence of calcite which will buffer pH changes... That the
calculations and modeling described below demonstrate that pyrite exists in sufficient quantity to
explain changes in pH and sulfate concentrations for a worst case example implies that the
mechanism will be valid for other wells at the site." Per the December 7, 2012 Pyrite report,
pyrite within the screened intervals of MW-3 A, MW-24 and MW-27 were detected at
concentrations of 0.1%, 0.8%, and 0.4% by weight respectively.
The December 7, 2012 Pyrite Report summarizes that: 1 mole of pyrite (FeS2) releases 1 mole of
iron hydroxide, 2 moles of sulfate, and 4 moles of hydrogen ions. Most of the sulfate generated
from the oxidation of pyrite is expected to be retained in solution which will raise the
concentration accordingly. Not all hydrogen ion released will lower the pH as it will react with
carbonate species in the water which will buffer the pH. Therefore, the more carbonate species
present, the more pyrite is needed to be oxidized to produce a change in pH.
If carbonate species are present there will be an impact in the ratio of sulfate concentration to the
change in pH. HGC notes that carbonate species are known to exist in the perched water and at
these locations; therefore, small changes in pH may be accompanied by relatively large changes in
sulfate concentrations.
HGC notes that the screening level calculations included in the report are calculated under ideal
conditions and may result in an overestimation of the actual pH decrease since the hydrogen ion
generated may react with other species. HGC conclusions, therefore, are useful to potentially rule
out pyrite oxidation as the sole mechanism for pH decrease if insufficient amount of pyrite are
available for calculation under ideal conditions for dissolution.
Assumptions used in the screening-level calculations and preliminary PHREEQC modeling:
1. Oxygen is not limited in the screening level calculations.
2. Oxygen diffuses into the vadose zone via the unsaturated portions of the well screens,
aided by barometric pumping, moving radially in all directions (including upgradient).
Because the relevant reactions occur upgradient, and affect water moving into a particular
well, groundwater flow and the potential resulting dilution from unaffected upgradient
water can be ignored.
3. Pyrite occurs only in the depth interval represented by the sample submitted for analysis.
HGC uses a higher porosity in the calculations than normally used in groundwater modeling for
the site (0.2 instead of 0.18). The higher porosity is considered conservative since a larger volume
of water, per volume of aquifer solid is assumed (100 g of water per Kg of aquifer).
Monitoring Well MW-3 A Calculation Results: The pH decrease in well MW-3 A from 2005 until
the 1st quarter 2011 was approximately 1 pH unit, and through the 2nd quarter 2012 was 0.4 pH
Page 29 of 41
EFR Source Assessment Reports
DRC Review Memo
units (due to an upward data trend during the latter period). Per the November 9, 2012 pH Report,
when the trend line is applied the change in pH is approximately 0.55 pH units. The HGC
calculations use the larger 1 pH unit decrease as a conservative measure.
HGC calculations:
Pyrite concentration of 0.0056% calculated for MW-3 A is equivalent to 5.6 x 10"5 g/g of the
formation (0.056 g/Kg of the formation) or 0.56 g pyrite/L of water.
Assuming a 120 gram molecular weight for pyrite this equates to 0.0047 moles pyrite/L of water.
Based on the molar release equation the maximum molar increase of pyrite in solution, based on
0.0047 moles pyrite/L water, is 0.019 moles/L.
HGC then calculates initial and potential maximum final concentrations of hydrogen ion for the 1
pH unit change, from pH 7.1 to pH 6.1 and found that the amount of hydrogen ion needed to
decrease the pH 1 unit is approximately 4 orders of magnitude lower than the amount that can
potentially be generated by pyrite oxidation per core sample analysis results.
HGC continued the evaluation to include sulfate concentrations, based on historical increases and
molar concentrations and found that there is "approximately 2 *A times more sulfate than needed
to account for the measured increase" The measured increase implies that only about 39% of the
available pyrite is oxidized and hypothesizes a continued decrease in pH at the well.
Monitoring Well MW-24 Calculation Results: Calculations in monitoring well MW-24 were
conducted in the same manner as well MW-3 A. Per the HGC conclusions, the amount of
hydrogen ion required to lower the pH to the conservative historical change, from 7.3 to 5.9 (1.4
pH units), is presently approximately 5 orders of magnitude lower than the amount available for
release through pyrite oxidation.
Based on evaluation of sulfate concentrations there is approximately 40 times more sulfate than
needed to account for the measured increase. The increase of sulfate of 310 mg/L is therefore
calculated to require approximately 3% of the pyrite available for oxidation. HGC concludes that
trends in pH and related parameters may be expected to continue.
Monitoring Well MW-27 Calculation Results: Calculations in monitoring well MW-27 were
conducted in the same manner as wells MW-3A and MW-24. Per the HGC conclusions the
amount of free hydrogen available at the location through pyrite oxidation to lower the pH from
7.3 to 6.7 is 5 orders of magnitude lower than what is available.
Sulfate calculation shows that there is approximately 60 times more sulfate than needed to account
for the measured increase of 70 mg/L. Per HGC this implies that only approximately 2% of the
available pyrite is oxidized and that trends in pH and related parameters may continue.
HGC additionally notes that the above calculations assume that all of the hydrogen ions released
by pyrite oxidation contribute to pH changes but that much of the hydrogen ions action will be
reduced by interaction with the aquifers dissolved carbonate species, including dissolved
bicarbonate and carbonate.
\
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EFR Source Assessment Reports
DRC Review Memo
PHREEQC Geochemical Preliminary Modeling Summary and HGC Conclusions:
Based on the visual and quantitative analysis, HGC additionally performed geochemical modeling
using the PHREEQC modeling platform to evaluate whether measured pyrite concentrations
contained enough pyrite to produce the observed pH declines. The modeling simulates a period of
25 years with anoxic conditions in the shallow aquifer (years 0-25) followed by 5 years of oxic
conditions (years 25-30). Model simulations account for formation porosity and notes that at well
MW-3 A where formation porosity is lowest, there is a greater amount of oxygen supplied by
groundwater than by air.
Pyrite consumption predicted by the second (oxic) set of simulations range from 3% to 33%,
based on the PHREEQC simulations most mineral phases remain stable while others tend to
change from unhydrated to hydrated forms (e.g. anhydrite tends to convert to gypsum and
kaolinite tends to convert to pyrophyllite).
The preliminary simulations predict changes in pH and sulfate concentrations similar to the
measured changes and also support pyrite oxidation as a mechanism for pH decrease and sulfate
increase in the site monitoring wells. The simulations also suggest that only a portion of the pyrite
has been consumed and that trends may continue in the future.
Monitoring Well MW-3A PHREEQC Preliminary Model Simulation
First anoxic run - Per the HGC conclusions, pyrite was stable in the anoxic simulation. The
second run by HGC which simulated oxic conditions indicated a decrease in pH of 0.4 su and an
increase in sulfate of approximately 330 mg/L. HGC notes that the simulated pH decrease is
"approximately equal to the change in pH suggested by the trend line in INTERA (2012b) and the
change in sulfate is similar to that used in the screening level calculation presented in Section
4.3.2.1." Based on the findings HGC concludes that these preliminary simulations support pyrite
oxidation as the mechanism for pH decreases at MW-3 A (33% of available pyrite consumed).
Monitoring Well MW-24 PHREEQC Preliminary Model Simulation
HGC preliminary results at well MW-24 showed pyrite stable in the anoxic run and a pH decrease
of 1.2 standard units and increase in sulfate of 225 mg/L during the oxic run. HGC notes that the
preliminary results are consistent with screening level calculations presented in Section 4.3.2.2
and that the conclusions support pyrite oxidation as the mechanism for pH decreases at MW-24
(6% of the available pyrite consumed).
Monitoring Well MW-27 PHREEQC Preliminary Model Simulation
HGC preliminary results at well MW-27 showed pyrite was stable in the anoxic simulation. The
oxic simulation showed a pH decrease of approximately 0.4 standard units and a sulfate increase
of approximately 60 mg/L. HGC notes that the pH changes are "similar to that suggested by the
trendline provided in INTERA (2012b) and the change in sulfate is similar to the value of 70 mg/L
Page 31 of 41
EFR Source Assessment Reports
DRC Review Memo
used in the screening level calculations provided in Section 4.3.2.3). Per HGC conclusions
regarding the preliminary simulation pyrite oxidation is supported as the mechanism for measured
pH decrease and sulfate increase at MW-27 (3% of available pyrite consumed).
HGC additionally notes that in cases where the aquifer contains large concentrations of carbonate
species, a large difference in dissolved sulfate concentrations will occur, whereas if the aquifer
contains low concentrations of carbonate then large changes in pH will cause relatively large
changes in pH sensitive analytes such as metals.
HGC concludes that pyrite oxidation "plays a significant role in perched water chemistry at the
site" and that changes in chemical species are dependent on the variable oxygen transport and
carbonate species concentrations in the aquifer matrix.
HGC Hypothesized Impact of Pyrite Concentrations on the Natural Attenuation of Nitrate
HGC hypothesizes that an additional factor in the natural attenuation of nitrate in the Burro
Canyon Aquifer is due to off-gassing of nitrogen (nitrogen reduction) by the oxidation of pyrite
and suggests that this mechanism may "help explain" the apparent stability of the trailing edge of
the plume.
Overall HGC Conclusions Related to the Pyrite Investigation
HGC considers the pyrite matrix concentrations and evaluation at monitoring well MW-3 A to be a
worst case example due to "relatively low detected pyrite concentrations (hundredths of mg/L)
which implies a relatively large mass ofpyrite has been oxidized, and because of the presence of
calcite (Table 4) which will buffer pH changes." HGC notes that even with these limitations the
preliminary geochemical modeling indicates sufficient pyrite to explain observed changes in pH
and sulfate concentrations and that this implies that the oxidation of pyrite at other locations
within the aquifer will be valid.
HGC notes that the preliminary PHREEQC geochemical modeling supports pyrite oxidation as
the mechanism for pH decrease since the results correspond to actual observed decreases and that
pyrite oxidation can be reasonably expected to have caused or contributed to rising trends for
other parameters (e.g. sulfate, TDS and metals).
HGC concludes that the oxidation of pyrite is driven by significant sources of oxygenated water
from the wildlife ponds as well as "enhanced oxygen transport into the vadose zone in the
vicinities of perched wells having screens extending above the water table." HGC additionally
notes that the low rates of perched water movement increase the residence time of groundwater in
contact with oxygenated vadose areas near the wells which will increase oxygen transport to
groundwater.
Page 32 of 41
EFR Source Assessment Reports
DRC Review Memo
DRC Findings Regarding the October 10, 2012 HGC Pyrite Report
Per DRC staff review of the Pyrite Report, it appears that the study was conducted in conformance
with Stipulated Consent Agreement Docket No. UGW12-03 which approved the EFR Pyrite study
as outlined in an April 13, 2012 "Plan and Time Schedule." Per review of the laboratory analysis
and conclusions of visual examination of polished sections as well as analysis of sulfur content
using an induction furnace, it was noted that Pittsburgh Mineral & Environmental Technology,
Inc. concluded that "pyrite cemented sandstone probably forms thin beds or lenses in this
formation. The pyrite usually forms massive cement that makes it difficult to determine the
mineral body size. It is also present as characteristic small cubes in the matrix between the sand
grains. Average Iron sulfide content is 5.8 volume %."
Results of the pyrite study were limited to 3 well boring locations which were assumed by HGC to
provide a representative sample of the entire Burro Canyon Aquifer. Although the study did not
provide a laterally extensive sampling of the aquifer matrix it is noted that the preliminary
investigation of the HGC worst case example (well boring MW-3 A) does provide evidence that
the oxidation of pyrite is a legitimate process, given a relatively low % of matrix pyrite, for
significant impact to geochemical processes and potential to induce chemical trends associated
with declining pH and associated increases in sulfate and indicator parameters.
The HGC mechanisms for introduction of oxygen into the groundwater are reasonable, based on
site characterization and well construction. The Pyrite Report therefore provides a reasonable and
possible explanation for the decreasing pH trends and observed increasing trends in indicator
parameters.
The Pyrite Report does not propose changes in Permit GWCL's, but does provide support for the
determination that current out-of-compliance parameters are due to background chemical
concentrations within the aquifer matrix and are not caused by the release of tailings solution to
the environment.
References:
Intera, October 2007, A Revised Background Groundwater Quality Report: Existing Wells for
Denison Mines (USA) Corp. 's Mill Site, San Juan County, Utah, Prepared by Intera Incorporated
United States Environmental Protection Agency 2009 Statistical Analysis of Groundwater
Monitoring Data at RCRA Facilities Unified Guidance, EPA 530/R-09-007.
Utah Division of Radiation Control, August 24, 2012, Groundwater Discharge Permit No.
UGW370004
Utah Division of Radiation Control, September 2009, Statement of Basis for Ground Water
Quality Discharge Permit UGW370004
Attachment 1
DRC HGC Core Screening and Collection Memo
Attachment 1
DRC HGC Core Screening and Collection Memo
MEMORANDUM
TO: File
THROUGH: Phil Goble, Compliance Section Manger
FROM: Tom Rushing, P.G.
DATE: September 10, 2012
SUBJECT: Utah Division of Radiation Control Inspection of the Energy Fuels Resources
(USA) Inc. Core Inspection and Sample Collection, regarding the pH Study, for
Monitoring Wells MW-23, MW-24, MW-28, MW-29 and MW-3A
Utah Division of Radiation Control (DRC) staff (Tom Rushing) met with Hydro Geo Chem.
(HGC) Representative (Stewart Smith) during the morning of Tuesday, August 14, 2012 to
observe the analysis of core samples and cuttings and collection of samples for the analysis of iron
pyrite. Specifically, it was DRC intention during this inspection to:
• Observe the cores available for sample collection at the subject monitoring locations
• Observe the screening process for core collection
• Observe the calibration and use of the X-Ray Fluorescence Metal Analyzer (XRF) Gun for
on-site environmental metals analysis of core and cuttings samples
• Observe the collection and logging of the cores
• Clarify laboratory analysis of the cores and cuttings
Core Investigation:
In relation to the preliminary screening of the cores and cuttings, DRC observed the following
practices to determine which intervals were considered most representative:
• Interval - initially all core boxes or bagged cuttings sample boxes were pulled from the
onsite core storage area, cargo boxes located west of the Mill office, and organized so that
the evaluation concentrated on core and cuttings within the vertical screened interval of the
corresponding monitoring well.
• Color - The core and cuttings samples were screened based on the color, core and cuttings
which were green/grey and grey were prioritized for further evaluation.
• Odor - It was noted that some intervals of core had an ammonia like smell which indicated
a reducing environment, these intervals were prioritized for collection.
• Appearance - Some intervals of core had yellowish or black flecking which were
potentially pyrite, and/or carbonaceous material and those intervals were prioritized based
on a possible reducing environment during deposition and more likelihood of higher pyrite
concentrations.
Summary:
Attachment 1
DRC HGC Core Screening and Collection Memo
• On site metals analysis - The XRF gun was used on priority sample intervals to determine
the concentration of iron in the core or cuttings sample. It was noted during the
investigation that the XRF gun did not have the capability to measure sulfur in the samples
and readings could not distinguish between iron oxide and iron sulfide (or other iron
minerals).
Per results of the screening, the HGC determined core intervals which were thought to have a
greater potential of higher pyrite concentrations.
XRF Gun Screening:
Per DRC observations the following was noted:
• The XRF Gun which was used onsite was rented from Geotech and was the Innov-X
Alpha Series with the capability to measure iron in the core and cuttings samples (parts per
million). DRC notes that it was HGC's understanding from Geotech that the XRF Gun
could also measure sulfur, however, a calibration standard was not included for sulfur and
upon follow-up with the company the XRF gun did not have that capability.
• The XRF Gun source was an X-ray tube W anode, 10-40 kV up to 5 selectable filters.
• HGC representatives calibrated the XRF Gun using the supplied source for iron.
• HGC representatives shot readings for all prioritized core intervals and compared the
readings.
• The highest reading noted was 9,770 ppm (monitoring well core MW-24
• Readings generally ranged between 200 ppm to 3,000 ppm
Sample Collection:
Per the results of the screening, HGC collected samples at the intervals showing the highest
likelihood of pyrite concentrations, the following samples were observed:
Monitoring Well Location Collection Interval Type of Sample
MW-23 108' BGS Core
MW-24 118.5'BGS Core
MW-28 88.5' BGS Core
MW-29 102'-103'BGS Cuttings
MW-3A 89.5' BGS Core
Samples were placed into ziploc bags and labeled accordingly.
Laboratory Analysis:
It was noted per discussion with HGC that the laboratory to be used for pyrite analysis had
changed since finalization of the 4/13/2012 work plan in groundwater monitoring wells. DRC
notes that the laboratory to be used was not included in the approved work plan.
Attachment 1
DRC HGC Core Screening and Collection Memo
Samples will be sent to a lab for visual examination and quantification of pyrite through the
creation of sample thin sections per methodologies outlined in the Stipulated Consent Agreement,
Docket No. UGW12-03.
Conclusions:
Per DRC review of the core collection methods, it was noted that cores required by Stipulated
Consent Agreement, Docket No. UGW12-03, screening, collection, labeling and photographing
appeared to be consistent with the approved work plan.
Attachments:
Attachment 1 - Photographs Taken During the August 14, 2012 Inspection
Attachment 2 - Geotech Handheld X-Ray Fluorescence Metal Analyzer Fact Sheet
Attachment 1
Utah Division of Radiation Control Inspection
White Mesa Uranium Mill
August 14, 2012 Core Inspection and Sample Collection for pH Study
Photo 1 - Example of intact core sample
44
Photo 2 - Example of HGC Representative using the XRF Gun
Attachment 1
DRC HGC Core Screening and Collection Memo
Photo 3 - Example of bagged cuttings sample (MW-29)
life I I k
Photo 4 - MW-23 Final Bagged Sample (108' BGS) and Core Box
Attachment 1
DRC HGC Core Screening and Collection Memo
Photo 5 - Final Bagged Core Sample MW-24 (118.5' BGS) and Core Box
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IPirnMtifflu
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Photo 6 - Final Bagged Sample MW-28 (88.5' BGS) and Core Box
Attachment 1
DRC HGC Core Screening and Collection Memo
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Photo 7 - Final Bagged Sample (MW-3A 89.5' BGS) and Core Box
1
Photo 8 - Final Samples for all collected during inspection (MW-29, MW-28, MW-24, MW-23;
MW-3A)
Attachment 2 - Geotech X-Ray Fluorescence Metal Analyzer Fact Sheet
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