Remedial Action at the Moab Site: Now and for the Long Term Letter Report (2002) / Chapter Skim
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Contents of Letter Report
Contents of Letter Report
Pages 7-26
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From page 7... ...
The Act also required DOE to ask the National Academy of Sciences to provide technical advice and recommendations to assist DOE in objectively evaluating costs, benefits, and risks associated with remediation alternatives for the Moab Site, including removal or treatment of radioactive or other hazardous materials at the site, ground water restoration, and tong-term management of residual contaminants. (See Appendix A for more background on the area and the site.)
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From page 8... ...
The unresolved questions are followed by some technical observations about the Moab Site and its remediation, provided at the end of the committee's report, in Section VI. ~ There is always the potential for new technologies and new alternatives to arise in the future, but in the case of uranium mill tailings the committee judges that these would be likely to create new specific remediation options, rather than new main alternatives.
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From page 9... ...
In addition, the residual natural uranium in the tailings solids continues to decay and generate new Th-230 and Ra-226. This decay will result in a future equilibrium concentration of Ra-226 in the tailings solids that, while tower than the current concentration, will remain higher than the EPA subsurface standard of 15 pCi/g.4 After the Th-230 has decayed to a concentration in equilibrium with U-23S, the concentration of Ra-226 will decline at a rate defined by the half-life of U-23S, which is 4.5 billion years.
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From page 10... ...
and the environment of alternative courses of action, as well as differences in the social value ascribed to the alternatives under consideration.5 In order to understand the risks associated with the primary remediation alternatives, one must characterize the pile and any sites involved. This has not been done adequately.
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From page 11... ...
If variances from baseline standards are sought or if significant recontamination is not prevented for the tong term, then the issue of protective standards should be revisitecl. Ammonias in ground water is reaching the Colorado River along the boundary of the Moab Site.
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From page 12... ...
If this mitigation can be carried out, there would appear to be no additional concerns under the ESA, provided that the dilution is carried out every year until the ground water is cleaned up. If, indeed, the ground-water plume must be cleaned up under any remediation alternative in order to meet Utah's water quality standards, then protection of endangered species should not determine the choice of how to deal with the tailings pile.
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From page 13... ...
The committee focuses on these issues, in part, because of the obvious presence of the Colorado River at the Moab Site. The focus is also, however, a result of the fact that other candidate sites and modes of transporting the tailings for the relocate alternative have not been examined in any substantial detail.
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From page 14... ...
The DPPR cites studies that conclude that the existing and previously proposed engineered barriers (a one-foot-thick compacted clay cover protected by several inches of sandy soil and a layer of rock armor) are sufficient to prevent significant infiltration of water into the pile, under the stabilize-in-place alternative [U.S.
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From page 15... ...
DOE cannot be expected to have an exact knowledge of the composition of the Moab pile. But DOE's considerable experience with the management of uranium mill tailings at other sites will help to determine whether DOE can assume that the tailings can be mocleled as regular ground-up rock or if more data should be collected to understand the likely long-term mechanical behavior of the tailings.~° These data could be collected in conjunction with the tests supporting calculations of contaminant flux, recommended below.
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From page 16... ...
DOE should try to put bounds on the present-day seepage rates from the pile. This seepage rate, once bounded, could be multiplied by an average contaminant concentration in the pile pore waters to estimate contaminant flux due to seepage, or multiplied by the maximum concentration in the pore waters to estimate an upper bound.
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From page 17... ...
, or "slimes." Continued consolidation of these materials after the cover has been emplaced could result in damage to the cover. The Moab Mill Reclamation Trust, formed after the bankruptcy of the Atlas Corporation, hired Steffen Robertson and Kirsten to develop a dewatering plan both to remove water in the pile as a source of further ground-water contamination and to consolidate the pile prior to emplacing the cover [SRK 20003.
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From page 18... ...
[Mussetter Ennineerinn 1994] concluded that the potential for migration of the modern-day Colorado River channel is tow for several reasons: the exit and entry points of the river to the Moab-Spanish Valley are bedrock-controlled; coarse-grained alluvial fans and deposits in the valley provide armoring to protect the river bank adjacent to the pile against lateral migration; in addition, the Moab marsh complex on the east bank of the river provides storage capacity for overbank flow, thereby reducing maximum shear stresses on the river bank adjacent to the pile.
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From page 19... ...
At the same time, DOE retains legal responsibility for physical conditions at the site and is responsible for the expenditure of significant amounts of taxpayer funds. Investing those resources in a way that strengthens institutional controls and social responsibilities for the Moab Site is an important component of the choices that DOE is making.
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From page 20... ...
Given the hazards and their timeframes, the best reasonably achievable solution for the Moab Site would involve a well-integrated set of near-term remediation actions and tong-term institutional management (LTIM) actions, where LTIM comprises the total system of protection, including contaminant reduction, contaminant isolation, and tong-term stewardship [NRC 20001.
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From page 21... ...
Of course, as noted in the opening pages of the committee's report, some hazards associated with the materials in the pile will persist forever. Thus, neither the memory of the mill tailings, nor the institutional controls to prevent human intrusion, nor the social capacity to repair engineered barriers can be assumed to be in place and sustainable in the future.
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From page 22... ...
That social contract can be shaped by public involvement, and it entails many matters lying beyond the scope of this committee's charter. The committee advises DOE to consider the coming decades, during which remedial actions are being carried out at the Moab Site, as a trial period for its LTIM plans in which it can test some of the hypotheses that have been made in its remeclial plans.
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From page 23... ...
sandbars and beaches could have significant impacts on the tourism industry, which uses riverbanks and bars as camping areas for river runners. This stretch of the Colorado River is one of the most widely used, and most famous, white-water rafting and kayaking regions in the world.
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From page 24... ...
to identify where the costs significantly exceeded early estimates, which could help DOE judge whether cost estimates for the remediation alternatives at the Moab Site are reliable and could be improved. DOE has shared gross cost estimates and first-order cost breakdowns with the committee.
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From page 25... ...
for treating the plume should be evaluatecl.~8 While designing reactive zones appropriate for the scale of application at Moab poses novel challenges, DOE's Environmental Management Science Program has funded research on several innovative approaches for treating radionuctide-contaminated soils and sediments [DOE 2002] , and some of these may also be useful for treating the contaminated plume at the Moab Site.49 There is also an opportunity at the Moab Site for treatment-system design to be based on a treatment-train approach (combinations of technologies)
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From page 26... ...
Modeled plumes from the site were shown to travel deeply into the ground water beneath the river, and to surface at varying locations. If such plumes exist then their impacts on the wetlands should be assessed.
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