ML20195H294
| ML20195H294 | |
| Person / Time | |
|---|---|
| Issue date: | 06/02/1988 |
| From: | Lohaus P NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Arthur W ENERGY, DEPT. OF |
| References | |
| REF-WM-72 NUDOCS 8806280261 | |
| Download: ML20195H294 (10) | |
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JUN 0 21989 W. John Arthur, III, Project Manager Uranium Mill Tailings Project Office Department of Energy Al>uquerque Operations Office P.O. Box 5400 Albuquerque, New Mexico 87115
Dear Mr. Arthur:
The NRC staff has completed its review of the draft Environmental Assessment (DEA) and the preliminary Design for the Spook, Wyoming, UMTRA project. As a result of this review, comments in the area of ground. water hydrology and geotechnical engineering are being sent under cover of this letter.
In addition, in the area of ground. water hydrology, the NRC staff completed and Plan (CRAP)g comments resulting from the review of the draft Remedial ActionAs you are a is providin the ground. water portion of the dRAP review upon receipt of the DEA, which DOE indicated would contain the majority of the ground. water data.
As a result of our review we find that DOE has not demonstrated compliance with the proposed EPA ground. water protection standards because of deficiencies with characterization of background ground. water quality, proposed water quality criteria, and selection of alternative actions for ground water protection.
Although our review of the information provided to date has not identified any i
flaws in the proposed design that would areclude compliance with the EPA standards, we are concerned with DOE's a)ility to meet the monitoring portion of the EPA ground. water protection standards. Again, it should be noted that the majority of the coments are on the DEA because the draf t Remedial Action Plan (dRAP) contained minimal ground-water information.
Should you have any question regarding the coments plerse contact Ssndra L.
Wastler of my staff at 492 0582.
Sincerely, Paul H. Lohaus, Chief l
8806200261 000602 Operations Branch PDR WASTE Division of Low-level Waste Management PDR WM-72 and Decomissioning DISTRIBUTION:
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NRC STAFF GROUND WATER COMMENTS ON THE SPOOK, WY, UMTRA PROJECT SITE DRAFT ENVIR0hMENTAL ASSESSHENT AND PRELIMINARY DESIGN DRAFT ENVIRONMENTAL ASSES 5 KENT Ground-water Hydrology 1.
DEA, Pages 60 and B-17, Delineation of Plumes in the Upper Sandstone Unit Pursuant to 40 CFR Part 192.12(c)(1), DOE is required to define the extent of ground-water contamination by listed constituents caused by seepage from the residual radioactive material. According to statements uade by 00E, the plume, in the upper Wasatch Sandstone have not been fully delineated. DOE intends to construct additional wells to alleviate this problem, however, the proposed plan to further characterize the extent of contamination, as briefly described on Page B-17, may not fully define the lateral extent of contamination NE of the site. According to the DEA, three wells will be installed in the upper sandstone unit to offset well 931.
In view of the proxinity of the Loma Pits to the proposed well locations, NRC staff recommends that DOE also install a monitor well northeast of well 924 and northwest of well 925 to establish the extent of contamination potentially caused by seepage from the Lona Pits. The staff anticipates the preliminary final EA and/or RAP to contain the pertinent ground-water informt. tion demonstrating compliance with the EPA standards.
2.
DEA, Pages 105 and B-24, Application of Subpart C, Supplemental Standards DOE intends to apply for supplemental standards under the provision that the aquifer is Class III. DOE asserts that "groundwater in the upper sandstone contains widespread ambient contamination resulting from naturally occurring conditions (related to the natural uranium mineralization) and from effects of broad-scale human activity (uranium exploration and mining activities), such that it cannot be cleaned up using treatment methods reasonably employed in public water-sup)1y systems." NRC staff agrees that the extensive uranium exploration in tie immediate vicinity of the site has altered the background levels of uranium and other listed constituents. The natural levels of uranium dissolved in ground water, and the remoteness of the site, greatly reduces the chance that a user will consune grm nd water in the upper sandstone aquifer.
The intention to apply supplemental standards notwithstanding, 00E is still required to select and perform remedial actions that come as close to meeting the otherwise applicable standard as is reasonable under the circurstances (40 CFRPart192.EE(a)). DOE is required to choose concentration limits for the listed constituents, and if they are ACL's, to demonstrate that they are as low as reasonably achievable and that they protect human health the environnent.
NRC staff finds that the above requirements are not satisfied in the DEA, because DOE did not discuss remedial action alternatives or propose concentration limits for the listed constituents.
o NRC staft suggests that DOE reconsider applying for su)plemental standards at the Spook site, and proceed with the intention that Su)part A will be met.
This removes the need to demonstrate compliance with 40 CFR Part 192.22(a),
leaving only the application for ACLs for those constituents predicted to be r
above background and the Maximum Concentration Levels. This demonstration may be less stringent and tinic consuming than the demonstrations required to select-and justify supplemental standards under 40 CFR Part 192.22(a).
3.
DEA, Pages 106 and B-25, Predictions of Concentrations for Listed Constituents The DEA does not adequately assess the rate and extent of migration of radium-226/228 and gross alpha, even though they were identified as listed constituents found in ground water resulting from the milling operations at Spook. DOE predicted downgradient concentrations oniv for uranium, selenium and nitrate by performing solute transport modeling. However, DOE did not assess migration of radium-226/228 end gross alpha.
In accordance with 40 CFR Part 192.20(a)(4), DOE is required to assess the rate and direction of novement of plumes of listed constituents, and assess future n.ovement, considering attenuation and dilution. Therefore, DOE should include the results of predictive analyses for radium-226/228, and gross alpha in the final EA and/or RAP.
4.
DEA, Pages 107 and B-4, Probability of Meeting the MCL's or Background Levels DOE did not adequately assess reasonable alternative measures that could be implemented to reduce infiltration and achieve compliance with maximum l
contaminant level (MCL's) or background limits for listed constituents in ground Water. DOE assumed that the embankment design will not meet the l
proposed MCL's or background levels downgradient of the mixing zone, and l
mentioned that the chances for ccmpliance improve if the infiltration barrier does not become fully saturated. However, DOE did not discuss alternative measures that could be incorporated into the design to achieve compliance with the EPA standards. For example, DOE did not examine (1) the use of thicker covers to lower infiltration rates into the tailings, (2) the use of e 'asal geochemical layer to lower constituent levels before the leachate enters the ground-water system, or (3) the use of a coarse-grained layer placed directly l
L above the infiltration barrier to effectively shed water off the pile.
In addition, DOE did not assess alternatives to design changes such as the application of ACL's for those constituents expected to exceed the MCL's.
Such alternatives should be considered by DOE to reduce constituent concentrations and achieve compliance with the standards.
00E will have to investigate options, such as those listed above, in its demonstration that constituent levels predicted to be above background or MCL's are as low as reasonably L
achievable and are protective of human hu.lth and the environment.
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5.
DEA, Page B-11, Background Characterization of Constituent Levels in the Upper Sandstone Unit of the Wasatch Formation DOE did not adequately characterize the background quality of ground water in the upper sandstone unit of the Wasatch Formation. Only one background sample was collected for ground water in the upper sandstone unit of the Wasatch Formation, and only one sample from two wells was collected for ground water in the lower sandstone unit of the Wasatch Formation. According to the revised Technical Approach Document (Page 151; DOE, 1987), background wells would be sampled at least twice to develop the data set.
EPA standards in 40 CFR Part 192.02(a)(3)(iv) require that a monitoring program be established that is adequate to determine background levels of listed constituents, llRC staff concludes that DOE's current mcnitoring program does not adequately characterize seasonal fluctuations or the spatial variability of backgreund water quality in this complex ground-water system.
Background characterization of ground-water quality is an extremely important aspect of the EPA ground-water protection standards because impacts to ground water are compared against background quality. Without adequate characterization of background quality, downgradient in:reases in constituent concentrations may be attributed to inadequate performance of the remedial action, whereas the real cause may be temporal or spatial variability of ambient ground-water quality.
NRC staff recomends that DOE further characterize the spatial and temporal variability of background ground-water quality by analyzing additional samples frcm the monitoring wells upgradient of the disposal pit.
6.
DEA, Page B-12, Discrepancy Between Text and Figure.
The text on Page B-12 is inconsistent with Figure B.3.8.
The text indicates that well 921 is completed in the lower sandstone unit and Figure B.3.8 indicates that the well is completed in the upper sandstone unit. The staff is inclined to believe that the well is completed in the deeper unit because the completion depth is listed as 175-185 feet in Table B.3.1.
DOE should resolve this inconsistency in the final EA and/or RAP.
7.
DEA, Page B-14, Characterization of Source Term DOE indicated that suction lysimeters will be installed to further characterize the source term present in the waste.
However, DOE has not mentioned how the data will be used af ter it is collected, or how the remedial action may differ depending on characterization results. As currently designed, the use of a basal geochemical layer or tailings amendment has not been discussed pending results of the analyses.
It appears that the data will be used solely as an input to a solute transport model. NRC staff suggests that DOE evaluate what alternative actions can be taken if the lysimeter data shows that the contaminant source will be present for long time periods.
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'8.
. DEA, Page B-20, Elevated Selenium Concentrations DOE's planned remedial action does not comply with the proposed EPA standards for ground-water protection in 40 CFR Part 192, Subparts A-C. DOE stated that selenium ' concentrations in well 916 are 235 times higher ~ than background: levels
- and 2100 times higher than the NCL's for selenium. From the discussion in the DEA, the assumed geochemical conditions.following remedial action will likely promote desorption and' dissolution of precipitated selenium and increase the-
- dissolved concentrations. However, DOE has not discussed proposed actions in.
the DEA or RAP that are specifically designed to lower these concentrations.
NRC staff concludes that DOE _should propose remedial actions to achieve compliance with the proposed ground-water protection standards.
9.
DEA, General, Ability to Implement Performance Ground-Water Monitoring Program DOEhasnotindicatedinthddEAhowitintendstomonitortheperformanceof the disposal site-after stabilization of the tailings in the pit. DOE's L
position in the Remedial Action Plan (Page 91) is that a decision to monitor
- ground water will be made_at a later date._ However,' EPA's proposed ground-water protection standards require monitoring to confirm initial performance.of the site. Therefore, DOE should propose at least the conceptual L
design of a monitoring plan in the RAP to ensure that the performance of the
- remedial action can be monitored. Of concern at the Spook site is the ability of a monitoring program to distinguish existing contaminaticn from potential future' contamination. Even more difficult will be how DOE's monitoring program
. will distinguish hazardous constituents releascu ' rom UMTRCA residual radioactive material and non-UMTRCA overburden material, which in some places contains higher concentrations of listed constituents than the tailings themselves. The final EA and/or RAP should include ; monitoring plan which L
addresses the issues listed above.
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DRAFT REMEDIAL ACTION PLAN Ground-water Hydology l'
'10.
dRAP, General, Ground-Water Re>wration Plan
" D0E.has not provided any discussion on restoration of ground water contaminated l
i
' by-past milling activities at the site, as required under Subpart B of 40 CFR l
Part 192. NRC staff has agreed that, in certain cases, DOE can defer ground-water restoration until EPA prorulgates final standards, provided that DOE demonstrates that disposal activities can be separated from clean-up l
activities, and that disposal options will not hinder impicnentation of L
restoration or clean-up plans in the future. DOE's selection of the pit
disposal option, however, may necesitate concurrent implementation of disposal and clean-up actions;to comply with proposed standards under Subpart A and B.
Thus, _D0E should either select appropriate clean-up actions to comply with the standards in Subpart B or demonstrate that clean-up can be deferred until after promulgation of the standards,
- 11. dRAP, Page D-70, Materials Used to Determine Hydraulic Conductivity DOE did not determine the hydraulic conductivity of cover materials by testing soils from the Spook site.
Rather, DOE estimated hydraulic conductivities by using test results from another UMTRA site, arguing that the grain size distributions of the materials were similar. HRC staff finds this method of material characterization unacceptable for material to be used in the cover because grain size distribution is not always a good indicator of hydraulic conductivity.
DOE should de.termine the hydraulic conductivities of cover material by testing representative samples of material from the Spook site.
PRELIMINARY DESIGN FOR REVIEW Ground-water Hydrology
- 12. Preliminary Design, Volume II, #3, Outdated Ground-Water Data The Prelimin6 y Design appears to be based on outdated information about the hydrogeology of the Spook site. The design documents, dated April 1988, contain the same ground-water information as the draft Remedial Action Plan, dated July 1987, even though the draft EA contains greatly revised ground water data. DOE should determine why information in the preliminary design and the EA do not correspond and demonstrate that the design submitted for review is still appropriate using the current knowledge of ground-water conditions.
- 13. Preliminary Design, Volume II, Calculation 07-715-00, Radon Barrier Design The proposed infiltration / radon barrier thickness is designed only for mitigation of radon release.
The cover has not been designed to minimize infiltration and achieve compliance with the EPA ground-water protection standards.
Given the thickness of the overburden to be backfilled above the stabilized tailings, it appears likely that a minimally thick layer would be sufficient to attenuate radon exhalation caused specifically from the tailings.
However, DOE should demonstrate that the cover system has also been designed to l
minimize infiltration and comply with the EPA standards.
- 14. Preliminary Design, Calculations 07-705-00, Foundation Preparation DOE does not appear to have considered recommendations from the State of Wyoming Abandoned Mine Lands (AHL) report for site 15-3 (Spook pit). The state
a recomends the use of a three-foot thick layer of material from the 900 pile and the western portion of the 800 nile, both of which are located on site to reduce leachate concentrations.
A*.'s leaching studies indicate that a significant percentage of dissolved contaminants could be attenuated by sorption onto 15e sandy material, thus significantly lowering contaminant concentrations in leachate. The staff considers the placement of three feet of on-site soil beneath the tailings to be a reasonable action that DOE should seriously consider during the development of this project. DOE should consider placing three feet of material beneath the tailings to reduce constituent concentrations in leachate, or demonstrate that placement is not necessary to achieve compliance with the standards.
Geotechnical Eng;mering
- 15. dDesign, Page 2 of Information for Reviewers, Foundation f or Tailings Embankment The basic conceptual design of the UMTRA aroject is to place contaminated material on a prepared foundation in the sottom of the Spook Pit and cover it with a low-permeability layer. The specifications require that the top six inches of the subgrade be at a minimum density of 90 percent standard proctor compaction. There is no other requiretent such as the depth of the foundation material to be stripped and compacted, material to be used, or the minimum thickness of the compacted layer beneath the tailings embankment.
Details of all aspects of this foundation preparation task should be clearly shown in the contract drawings, and also included in the specifications. The AML backfill (mine waste) will be placed on a prepared foundation layer of 3-feet-thick, compacted, fine grained material from the 800-mine wasta pile.
The AHL report (page 7A-23 of Appendix 7 to AHL report) suggests that a 3-feet-thick compacted layer of fine grained material from the western portion of the 800 pile, 900 pile or material excavated from the northern channel may be used as a bedding or liner beneath the tailings embankment. This layer would result in the additional benefit of retarding the transport of contaminants through this layer by approximately 1,000 years. Since DOE is comitted to take all feasible measures to reduce the groundwater contamination, this recommendation in the AML report should be seriously considered for implementation.
(see coment on this item by groundwater hydrologist).
- 16. dDesign, Page 2 of Information for Reviewers, AHL Backfill Above Tailings The statement that the upper 18 or more feet of backfill will have materials with less than or equal to 0.2 or 0.1 ppm of Se and 5.0 pCi/gm of Ra-226 or less is not consistent with the statements in the AHL report that designate this material as Zone 3 material containing less than 20 pCi/gm of Ra-226. The AHL program considers material with less than 20 pCi/gm of Ra-226 to be a clean fill, whereas DOE /UMTRA considers 5 pCi/gm of Ra-226 as the upper limit for a L
clean fill. 00E should officially indicate which material is defined as residual radioactive material, low-grade ore or clean overburden. NRC staff understands that redon flux calculations do not consider the effects of exhalation from overburden material.
However, DOE is considered responsible for the long-term stability of the residual radioactive material, and thus are responsible for ensuring that overburden placement does not compromise the integrity of the tailings embankment. DOE should provide assurances that the overburden material will be placed according to design specifications because of the relationship between overburden placement and tailings stability.
17.
dDesign, Page 3 of Information for Reviewers, Construction Sequence resent thinking of the DOE is that both the DOE /UMTRA program and the The p/AML program will be constructed by the same subcontractor, and portions State of both may be constructed concurrently. The preliminary design calls for a 1.5 feet thick low-permeability layer to cover the tailings embankment which has a side slope of 2H:1V. This in turn will be covered with mine waste backfill placed under the AML program. The tailings and the AML backill are specified to be compacte<i to 90 % standard proctor density whereas the thin (1.5 feet thick) low-permeability layer, sandwiched between these two materials, is specified to be compacted to 95 % standard proctor density. This is difficult to accomplish even if a single subcontractor works concurrently on both the UMTRA and AHL projects. The DOE should present details in the final RAP on how this will be constructed to strict compliance with the design thickness and compaction specifications presented in this preliminary design.
Consideration may be given to the options of either increasing the thickness of the low-permeability layer or changing the compaction specifications.
- 18. dDesign, Calculation 07-720-00, Radon Barrier Design The design of the radon barrier and value of the hydraulic conductivity of the infiltration barrier layer, presented in the preliminary design, are based on very limited site specific test data, and are therefore considered to be preliminary. The NRC staff expects the design to be presented in the final RAP to be supported by adequate test data.
- 19. dDesign, Construction Sequence - Item 1.3.C.7, page 01010VA-4 of the Subcontract Document Item 7 iniplies that the tailings embankment construction will be completed before initiating construction of the low-permet.bility cover layer.
This contradicts the current thinking of concurrent construction of both UMTRA and AHL programs by the same subcontractor. This item should be modified to reflect the current thinking of concurrent construction.
L 20.
dDesign, Borrow Area Location - Item 1.4.A, page 01010U-4 of the Subcontract Document.
Contrary to the statement in the above item, the location of the borrow area A is not shown in the subcontract drawings. The location or the borrow area should be shown in the subcontract drawings.
- 21. dDesign, Unidentified Waste - Item 1.2.C.4, page 020500-2 of the Subcontract Document.
For disposal of unidentified waste, reference is made to the standards uf the Colorado Department of Health. The reference should be to the standards of the Wyoming Department of Health as the site is in the state of Wyoming.
- 22. dDesign, Equipment - Item 2.4, page 022000-9 of the Subcontract Document.
This section provides guidance on the equipment intended for compacting granular material only. However, there is clayey material to be compacted for the low-permeability cover layer over the tailings embankment. The specifications should include guidance, similar to that provided for the vibratory roller, for the equipment to be used for compacting the low-permeability cover material.
- 23..dDesign, Cocpaction Requirements - Item 3.5.C.2, page 02200U-16 of the Subcontract Document.
This item specifies the moisture content range for compaction of the low-permeability cover layer only. To be consistent, this item should also provide guidance on the moisture content range for conpaction of the tailings material also.
24 dDesign, Backfilling Mine Drifts - Item 3.6.A, page 02200U-17 of the Subcontract Documents.
The' specifications for this item of work are very general and do not provide any specific details on the material to be used, placement control etc.. This section should be revised to provide detailed specifications for this item of work.
- 25. dDesign, Field Quality Control-Item 3.7.B.1.b, page 02200U-17 of the Subcontract Docun4ent.
The testing frequency for the low-permeability cover material is one test for every 500 cyd of material placed. Since the volume of this material to be placed is only 13,600 cyd and the construction sequence nay require placement of a limited quantity at a time, the testing requiremen; should include that at
.least one test be performed every day that over 100 cyd, of material is placed and a minimum of one test be performed for every lift and every full shift of compaction operation.
- 26. ' dDesign, ? ayment for Inspection Pits-Item 1.6.B.5, page 02200A-6 of the P
Subcontract Document.
The inspection and testing frequencies for the AML material.to be placed directly above the DOE tailings embankraent should be identichl to those used by the DOE for placement of cover material on UMTRA projects.
- 27. dDesign, Drawing SPK-AML-PS-10-0206.
This drawing should shew the tailings embankment constructed under the DOE /UMTRA contract, as this will impact on the volume of backfill to be.placed under the ANL program.
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