DRC-2011-007125 - 0901a068802579c4

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Thomas Rushing ii - Phases 4 and 5 Draft description for the nitrate investigation at White Mesa MiU
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Kathy Weinel <[e-mail]>
"[e-mail]" <[e-mail]>
7/27/2011 5:20 PM
Phases 4 and 5 Draft description for the nitrate investigation at White Mesa Mill
"[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>, Phillip Goble
<[e-mail]>, "[e-mail]" <[e-mail]>,
"[e-mail]" <[e-mail]>, Dan Erskine <[e-mail]>, David Frydenlund
<[e-mail]>, "JoAnn Tischler" <[e-mail]>
Attachments: PHASE 45 modified 7 272011 .docx
Tom,
As per your discussions with Jo Ann Tischler, attached for your review is a draft description of Phases 4 and 5 for
the White Mesa Mill Nitrate Investigation.
Please feel free to contact me if you have any questions regarding this transmittal.
Kathy Weinel
Kathy Weinel
Quality Assurance Manager
t: 303-389-4134 | f: 303-389-4125
1050 17th Street, Suite 950
Denver, CO, US, 80265
DENISON MINES (USA) CORP
www.denisonmines.com
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file://C:\Documents and Settings\Trushing\Local Settings\Temp\XPgrpwise\4E3048E7EQDOMAlNEQRAD1001726274176... 7/28/2011
PHASE 4 -Stable Isotopic Sampling and Analysis
The purpose of the Phase 4 isotopic sampling and analysis is to provide additional data, if required, to
support or reject hypotheses presented in the Nitrate Investigation Phase 2 to 5 Work Plan, including
the hypothesis of a natural nitrate source and hypotheses regarding Mill site sources.
The stable isotopic composition of nitrogen, oxygen (NO3, NH4) and sulfur (SO4) will be measured in well
samples from the White Mesa Mill Site to attempt to determine the source and degree of mixing of
these compounds in groundwater in light of chemical and hydrologic data already available. Samples
will be collected for nitrate (5^^N, S^VNOB), ammonium (6^^N ) and sulfur (6^''S, 5^^0-S04) isotopic
analysis from selected well locations based on existing conceptual models, to attempt to determine
isotopic fingerprint or ratios in groundwater in the selected wells. Each well will be purged and
monitored until key parameters stabilize. Samples will be collected and analyzed for:
1} analytical concentration of dissolved nitrate, ammonium, chloride and sulfate (using EPA
Method 300.0), and
2) isotopic composition.
All samples will be preserved, shipped and analyzed in accordance with a new QAP to be deiveloped for
isotopic groundwater sampling and analysis. This new QAP (the "Phase 4 QAP") will specify the specific
details, activities, equipment, procedures, objectives, schedules, laboratories and decision criteria for
this phase of the investigation. The Phase 4 QAP will be based upon and utilize the existing DRC-
approved QAP for groundwater sampling at the Mesa Mill. The Phase 4 QAP will follow the same
outline as the existing approved QAP for groundwater sampling at the Mill and will supplement the
approved QAP to address those activities which are specific to Phase 4 of the nitrate investigation.
The Phase 4 QAP will address the following additional requirements:
• Schedule for sampling
• Sample turnaround
• Selected laboratory(ies)
• Analytical Methods
• Sample volumes
• Minimum detection limits for analytes
• Field Quality Assurance procedures
• Laboratory Quality Control
The Phase 4 QAP will be submitted to DRC on or before September 16, 2011. The schedule assumes
DRC witl complete review by October 7, 2011 and DUSA will submit a Final Phase 4 QAP by October 28,
2011. Sampling will be completed by January 31, 2012 ^
Wells will be sampled along a transect essentially north to south through the long axis of the nitrate-
chloride plume approximately parallel to the estimated direction of ground water flow. Wells that will
be sampled within the mapped nitrate - chloride plume (Figure 22) include TWN-3, TWN-2, TW4-22,
TW4-24, and MW-31. Similarly, wells will be sampled from within the separate nitrate - chloroform
plume to characterize the nitrogen accompanying infiltration from the septic leach fields (TW4-18, TW4-
11 and TW4-1). Well locations containing elevated tritium indicating the ground water contained a
component of recent recharge (Hurst and Solomon, 2009), will be sampled forthe isotopes listed above
to expand the application of these results to potential surface sources (MW-30, MW-27 and MW-19, in
addition to MW-31 already identified). In addition, water samples will be collected from two(2) distmct
occurrences of elevated nitrate in groundwater upgradient and NE ofthe Mill Site plumes, and from one
downgradient location> SW of the Mill Site, to determine if the nitrate sources are similar or if there is
continuity of transport processes across the site (TWN-19, TWN-17, TWN-9, and MW-20) (Figure 22).
Two specific technical concepts are incorporated in this Isotopic Phase to improve the probability of
interpreting what is often an inconclusive overlap of signature for nitrogen isotopic data in
discriminating among multiple sources. First the 6^^0 of both sulfate and nitrate moleculejs will be
analyzed, because the exchange of oxygen isotopes in these molecules occurs in both atmospheric arid
aqueous environments. The consequence ofthis analysis is that different ^^Of^O ratios are indicative of
the antecedent environment, which further contributes to Interpretation of solute source and
evolutionary pathway.
Secondly, nitrogen may be present as ammonium in the ground water in wells affected by septic leach
field drainage, or Infiltration from the historical pond or natural wildlife ponds. If nitrate and /or
ammonium are detected In the groundwater chemical analysis, then the sample will be tested for 5^^N
of ammonium as well as nitrate.
PHASE 5 -Isotopic Soil and Product Sampling and Analysis
A determination regarding the necessity to complete Phase 5 will be made after review of the
data obtained from the previous phases of the nitrate investigation. For example, if the isotopic
values of nitrogen and sulfur in ground water samples analyzed in Phase 4 indicate that a
distinction can be made among potential sources, then Phase 5 will be pursued. The objective of
this phase is to identify potential and possible endmember source candidates and characterize the
nitrogen and sulfur isotopic composition according to the criteria described in Section 2.3.3.1 of
the Nitrate Investigation Phase 2 to 5 Workplan. This sampling will include:
(a) Any soils and/or bedrock that Denison determines could represent a natural nitrate
reservoir.
(b) Any soils and/or bedrock representative of any of the Phase 1 or 3 Mill site sources that
Denison and the executive Secretary agree, based on the results from Phase 1 or Phase 3,
could have contributed to the plurne, and
(c) Influents to any sewage vault or leach field identified in paragraph B as requiring isotopic
analysis.
Each sample will be collected and analyzed for:
1) Concentrations of dissolved nitrate, ammoniuni, chloride, and sulfate (using EPA
Methods to be identified in the QAP and Sulfate Method 300.0); and
2) Isotopic composition.
Samples will be collected for nitrogen, oxygen S'^O-NQs), and sulfur (6^^S, 6*^0-S04)
isotopic analysis according to the criteria in Section 2.3.3.1 of the Nitrate Investigation Phase
2 to 5 Workplan to evaluate the possibility of each being a source.
Representative leach samples will be collected from background alluvial boring sediments
from three (3) natural nitrate reservoir locations and three (3) gypsum lithologies for nitrogen
and sulfur isotopic composition respectively. Samples from each boring or medium will be
collected at approximately the same intervals as specified in Phases 1 and 3 for non-isotopic
characterization in the Nitrate Investigation Phase 2 to 5 Workplan. Since isotopic results
from these potential samples will be compared directly to isotopic fingerprints of
groundwater, background samples are not required.
All sample's will be collected, preserved, shipped and analyzed fallowing a separate QAP to
be developed for isotopic sampling and analysis of soil, extracts, and manufactured products.
The QAP will be submitted specifying the specific details, activities, equipment, procedures,
laboratories, procedures, schedules, and decision criteria for this phase of the investigation.
The QAP will be based upon and utilize existing DRC-approved QAP for groundwater
sampling at the Mesa Mill. The QAP will follow the same outline as the approved QAP and
will supplement the approved QAP to address those activities which are specific to Phase 5
of the nitrate investigation.
The QAP will address the following additional requirements:
• Schedule for sampling
• Sample turnaround
• Selected laboratory(ies)
• Analytical Methods
• Sample volumes
• Minimum detection limits for analytes
• Field Quality Assurance procedures
• Laboratory Quality Control
The QAP Addendum will be submitted to DRC on or before June 29, 2012. The schedule
assumes DRC will complete review by July 20, 2012 and DUSA will submit a Final QAP by
August 10, 2012. Sampling will be completed by September 7, 2012.