DRC-2011-006637 - 0901a06880246e32

State of Utah
GARY R. HERBERT
Governor
\
GREG BELL
Lieutenant Governor
June 23, 2011
Department of
Environmental Quality
Amanda Smith
Executive Director
DIVISION OF RADIATION CONTROL
Rusty Lundberg
Director
0 66
CERTIFIED MAIL
(Return Receipt Requested)
David C. Frydenlund, Vice President, Regulatory Affairs and Counsel
Denison Mines (USA) Corp.
1050 17* Street, Suite 950
Denver, CO 80265
Subject: Nitrate Investigation Revised Phase 2 to 5 Work Plan dated June 3, 2011: DRC Review
Comments
Dear Mr. Frydenlund:
DRC review comments regarding the June 3, 2011 Denison Mines (USA) Corporation (DUSA) "Nitrate
Investigation Revised Phases 2 through 5 Work Plan" are enclosed (via URS Memorandum). Please
ensure that all comments are address and resolved in the revised version ofthe Phase 2 through 5 Work
Plan (Rev. 1.0).
If you have questions or concems regarding the comments, or would like to arrange a meeting or
teleconference to discuss the comments, please contact me at [phone]. Thankyou.
Thomas Rushing, P.G.
Geotechnical Services Section
Enclosure: URS Memorandum (5 pp)
F:\DUSA\Nitrate Contamination Investigation\Work Plan Phases 2-5\Rev. ONPhase 2-5 Workpian Rev 0 DRC Comments Cover Ltr.doc
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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MEMORANDUM
To: Tom Rushing (DRC), Loren Morton (DRC), Phil Goble (DRC)
From; Paul Bitter (URS), Jeremy Cox (URS)
cc: Robert Baird (URS) .
Date: 23 June 2011
Re: Comments on the Nitrate Investigation Revised Phase 2 to 5 Work Plan for White
Mesa Mill Site dated June 3, 2011
This memorandum contains the URS and DRC comments on the Revised Phase 2 to 5 Work Plan
for White Mesa Mill Site (Work Plan) dated June 3, 2011, which was prepared for Denison Mines
USA (DUSA) by Intera Corporation. This review has been performed as a deliverable for
Contract No. 116259 issued through the Utah Department of Environmental Quality, Division of
Radiation Control (DRC). This review also is in accordance with the amended Memorandurri of
Understanding (MOU) between the DRC and DUSA dated April 28, 2011. For purposes of
expediency, the URS and DRC comments are edited for conciseness and combined into one
memo. Note that format, grammar, and punctuation were not reviewed for accuracy and
consistency.
The comments regarding the Work Plan are presented below.
1. General Comment: The Work Plan is well-organized. The initial conceptual site model
incorporates good information that will benefit the evaluation of potential sources of the
nitrate and chloride in groundwater at the site.
2. Global comment: The Decision Process Logic implies that if the vadose zone concentrations
(mass) are less than background concentrations (mass), then the possible source under
consideration is removed from the source candidate list and groundwater will not be
analyzed. DRC disagrees with this implication. Groundwater must be analyzed throughout
the site in order to dismiss potential sources. We presume based on the fate and transport
discussions in the work plan, and underscore herein, that groundwater hydraulically
downgradient of potential sources and within a distance comparable to the travel time of a
release from a potential source is linked to the potential source. This forces consideration of
increasing trends (if any) in grouhdwater that can be linked to an upgradient source. The
vadose zone characterization indicates what will be transported to the groundwater in the
future. Historical sources of nitrate and chloride may have resulted in groundwater
contamination downgradient of the historical source that may still be present even if the
nitrate is no longer present in the vadose zone at the former source area. The lack of nitrate
concentrations or mass in the vadose zone at a potential source area, alone, is insufficient
Page 1 of 5 URS
evidence to dismiss a source area. Thus, evaluation of potential sources has to include the.
concentrations in groundwater up to the travel distance equivalent to the time frame of a
potential release from each potential source. This factor appears to be addressed in the
"necessary conditions" sections for the hypotheses in Section 2.3.3.1. Concentrations and
mass of nitrate and chloride in the vadose zone should be one component of the weight of
evidence approach to identify or dismiss potential sources of nitrate contamination in the
groundwater. Please revise the decision logic diagrams and text accordingly.
3. Global comment: Cryptosporidium is a marker of cattle contribution to groundwater
contamination; however, the presence of Cryptosporidium does not mean that all nitrate in the
groundwater near a specific potential source is due to cattle management activities.
Cryptosporidium should be one component of the weight of evidence approach to identify or
dismiss potential sources of nitrate contamination in the groundwater. Please revise the
decision logic diagrams and text accordingly.
4. Global comment: Ahhough the decision logic process may imply that an isotopic fingerprint
may uniquely identify a specific source, the isotopic fingerprint may not conclusively link
nitrate in a source area to the nitrate in the groundwater. Instead, isotopic analysis should be
one component of the weight of evidence approach to identify or dismiss potential sources of
nitrate contamination in the groundwater. Please revise the decision logic diagrams and text
accordingly.
5. Section 1.1.1.1: Although procedures for the Phase 2 sampling may be presented in the
Phase 2 QAP, sampling locations can be selected at this time based on the groundwater data.
Groundwater sampling locations were presented in the first iteration of the nitrate
investigation work plan, and DRC recommended several additional groundwater sampling
locations in subsequent meetings. Due to the anticipated schedule for delivery ofthe Phase 2
QAP and Revision 1.0 of the Phase 2-5 Work Plan versus the schedule for the Phase 2
sampling, the locations previously agreed upon in these meetings should be shown on a figure
in the Phase 2 QAP and Revision 1.0 of this Work Plan, and discussed in this section of the
text or elsewhere in these documents; as appropriate. The Phase 2 sample locations should
be listed in a sampling table in the Phase 2 QAP and Revision 1.0 of this Phase 2 through 5
WorkPlan.
6. Section 1.1.1.2: Although specific locations for Phase 3 sampling cannot be specified until
receipt of data from the Phase 1 investigation, the Phase 1 data should be available before the
anticipated delivery of Revision 1.0 of the Phase 2-5 Work Plan. Phase 1 sampling activities
were completed on approximately June 12. Typical laboratory turn-around times are on the
order of three weeks for conventional analyses such as the ones being performed for Phase 1.
Therefore, the laboratory likely would be able to deliver the analytical data to DUSA by mid-
July at the latest. DRC requests that the draft report for Phase 1 sample results be submitted
to DRC prior to, or concurrent with. Revision 1.0 of the Phase 2-5 Work Plan so that the
Phase 1 data can be used to justify the Phase 3 sampling locations.
7. Section 1.1.1.3: Refer to the DRC comment on Section 1.1.1.1. Locations of monitoring
wells at which isotope sampling would be conducted were also previously submitted with the
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first iteration of the nitrate investigation work plan, and were subsequently modified during
meetings between DRC and DUSA earlier this year. DRC does not see any reason why the
locations for the isotope analyses would require modification from the previously agreed-
upon locations. The locations previously agreed upon in these meetings should be shown on
a figure in Revision 1.0 of this Work Plan, and discussed in this section of the text or
elsewhere, as appropriate. The Phase 4 sample locations should be listed in a sampling table
in Revision 1.0 of this Phase 2 through 5 Work Plan, with the columns left blank if the details
need to be presented later in the Phase 4 QAP.
8. Section 1.1.3, last paragraph, fourth and fifth sentences: Please remove the quotations marks
at the beginning and end of these sentences.
9. Section 1.2.2 and Section 1.5: DRC prefers that a standard USGS or other national
publication be used to guide descriptions of rock cores instead of the New York Department
of Transportation.
10. Section 2.2.4, third paragraph: The units for the estimated hydraulic conductivities should be
centimeters per second (cm/s), not cubic meters per second.
11. Section 2.2 4, fourth paragraph: The discussion of groundwater travel time between
monitoring wells TWN-2 and MW-31 is helpful. However, the estimated travel time
presented in this paragraph is based on two assumptions that must be listed in this text: (1) the
nitrate and chloride in the groundwater at MW-31 originated from a single source in the
vicinity of TWN-2, and (2) the dissolved nitrate and chloride travel directly downv^ard
through the vadose zone from the point of discharge at the surface to the groundwater, with
no lateral spreading due to the Mancos Shale or Dakota Sandstone/Burro Canyon Formation.
As discussed in Section 2.3, the latter assumption is unlikely.
12. Section 2.3: The discussion of the migration pathways is detailed and appropriate. Several
inferences are made regarding the effect of the Dakota Sandstone/Burro Canyon Formation,
the Maricos Shale, and the interface between the Mancos Shale and the alluvial material on
migration of contaminants. DRC requests that DUSA further explain in this Work Plan these
lithologies' effects on the chloroform plume relative to the presumed sources of the
chloroform contamination.
13. Figure 4: There is no figure in this Work Plan showing the locations of the potential source
areas that are listed in the text. These areas are relevant to Phase 3 and the conceptual site
model. Figure 4 would be an ideal location where the potential source areas could be
displayed relative to the groundwater plumes. Please remove the wells from Figure 4 and add
the potential source areas to this figure.
14. Figures 6 through 10: These figures do an excellent job of illustrating the conceptual site
model. However, the hatching for the groundwater plumes obscures some of the cross
section. Please use a less dense pattern for the groundwater plumes so that the soil types can
be seen more clearly.
15. Figures 13 and 14: Please revise these figures to show groundwater mounding below the
surface pond and include the interpretation as related to differences in groundwater flow
paths and velocities (increased hydraulic gradient).
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16. Figures General: DRC requests that an additional figure be included in the work plan
consisting of an isopach map (2 dimensional) to depict extent and thickness of the Mancos
Shale paleoridge and including location plots of all boring locations completed for Phase 1, as
well as the locations of potential sources of nitrate contamination in the study area (as listed
in the Work Plan Section 2.3.3.1).
17. Section 2.3.3.1: Several of the discussions regarding potential sources and their fate and
transport are nearly identical and could be consolidated into one discussion pertaining to
groups of sites. DRC suggests that any nearly identical sections be consolidated.
18. Section 2.3.3.1, Main Leach Field, Decision Process: DRC requests multiple edits to the
logic detailed here and elsewhere in the report for other potential source areas. (1) The
weight of evidence approach should be used to determine whether potential source areas can
be ruled out. By definition, this approach incorporates multiple hnes of evidence. A single
line of evidence, such as a hydrogeological evaluation, will not be sufficient to rule out most
of the potential source areas. (2) DRC reserves the right to determine whether a potential
source is ruled out. (3) The lack of nitrate or chloride in alluvial soil or bedrock below a
potential source area is not sufficient evidence to rule out that site as a contributing source. It
is possible that the nitrate and chloride in the groundwater are the result of a historical
release. If the release ceased but a source of uncontaminated water continued through the soil
column over time, most or all of the nitrate and chloride could have been removed from the
vadose zone. An example would be a leach field in which process chemicals containing
ammonium and chloride were historically discharged. After the discharge ceased, the
continued operation of the leach field could have contributed water free of nitrate and
chloride that removed the nitrate and chloride from the soil column over rime and deposited
them into the groundwater. For this reason, the soil data alone should not be used to rule out
a potential source, nor should soil data alone be sufficient reason to rule out groundwater
sampling. (4) The soil isotopic analyses for Phase 5 were intended to be for alluvial soil, not
bedrock as stated here. Please revise this text and the text for all of the subsequent potential
sources accordingly.
19. Section 2.3.3.1, Historic Pond, Hypothesis 16-2: DRC notes that the analysis of aluminum in
soil to test this hypothesis will be unreliable. Aluminum from rocket motor testing is unlikely
to behave in the same manner as ammonium or chloride, and site-specific background
concentrations of aluminum in soil likely are not currently available and could have a wide
variation. Instead, DRC reinforces analyzing for nitrate, chloride, and perchlorate as
discussed in the Phase 2 through 5 Work Plan.
20. Section 2.3.3.1, multiple sections: The presence of oxygen in the pore space in subsurface
soil is likely to provide sufficient oxygen to convert ammonium to nitrate. A source of
oxygenated water may not be the sole source of oxygen needed for the nitrification, although
the water would be necessary for the transport of the nitrate to groundwater.
21. Section 2.3.3.1, multiple sections: for all text regarding "nitrates and chloride associated with
sewage" please modify the text to discuss "nitrates and chloride originating from sewage or
process chemicals".
Page 4 of 5 URS
22. Sections 2.3.3.1, multiple sections: the concentrations of all groundwater analytes must be
compared against a background level for the site or region. This includes perchlorate,
Cryptosporidium, or any agriculturally-used chemicals. If reliable literature values for these
analytes are not available, DRC requests that DUSA sample a statistically-significant number
of inonitoring wells that do not contain elevated concentrations of nitrate or chloride to
determine a background level. The details regarding detentiination of background levels
may be deferred to the Phase 2 QAP, but the comparison against background levels must be
mentioned in Revision 1.0 of this Work Plan.
23. Section 3.7.3.5: During the review of the QAP, DRC may require third-party data validation
for groundwater analytes not included in the original QAP.
24. Figures 15-18: Refer to global comments and comment on Section 2.3.3.1, Main Leach
Field, Decision Process. The conclusions on the flow diagrams should be modified
accordingly.
25. Table 1: Per communication between DRC and DUSA on 6/8/11, the Phase 2 and Phase 4
QAP are to be stand alone documents and are not to be Addenda to the QAP currently
approved for the White Mesa Ground Water Permit, Permit No. UGW370004. This is based
on this sampling and analysis being a one time event and specific to the Nitrate Investigation
Project. Please ensure that all language referring to either of the Phase 2 and Phase 4 QAP's
as an "Addendum" is removed and that Revision 1.0 of the Phase 2-5 Work Plan clarifies that
these QAP's will be stand alone documents.
26. Table 1: The long time for isotopic analyses by the laboratory (5-6 months) appears to be
unreasonably long. Please jusfify why this time would be required for the laboratory
analyses.
[End of comments]
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