Ward Valley An Examination of Seven Issues in Earth Sciences and Ecology (1995) / Chapter Skim
Currently Skimming:
EXECUTIVE SUMMARY
EXECUTIVE SUMMARY
Pages 1-14
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 1... ...
California, Arizona, North Dakota, and South Dakota formed the Southwest Compact to share a disposal facility for these wastes. The Ward Valley site west of Needles, California.
|
From page 2... ...
: GENERAL CONCLUSION: The committee concludes from multiple lines of evidence that the unsaturated zone at the Ward Valley site is very dry, and that recharge or potential transfer of contaminants through the unsaturated zone to the water table, as proposed by the Wilshire group, is highly unlikely. However, because of the limitations of the data, the committee recommends specific initial baseline and subsequent monitoring measurements, summarizes!
|
From page 3... ...
and the presence of tritium in the unsaturated zone (subissue (3~.3 The majority of the committee considers that subissue Aid, unsaturated zone variability and complexity, has been adequately addressed in the modeling aunt analyses of the unsaturated zone, with the exception of the modeling of a complete cover failure; subissue (2) , the presence of preferential pathways, is not supported by any consistent evidence for rapid downward water migration or ground water recharge below the site, despite arguments to the contrary3, as discussed later in this Executive Summary; subissue (4)
|
From page 4... ...
Limitations of Field Data at the Ward Valley Site The committee notes that monitoring hydraulic parameters in dry soils like those at the Ward Valley site is very difficult and may be one of the causes of the Dictations in collecting field data. Limitations of field data during site characterization are grouped into three classes: (~)
|
From page 5... ...
This recommendation is also discussed later with reference to monitoring. Specific Recommendations · As water content and water potential monitoring, tritium analyses, and ground-water levels are proposed for operational and post-closure monitoring, the committee recommends several actions to establish base levels for monitoring, including additional testing for tritium, sampling for chIorine-36 (36cl ~ to help resolve the reported tritium found in the unsaturated zone, - drilling and sampling of the unsaturated zone from well below the current characterization depth of 30 meters, and further investigation of the apparent vertical hydraulic gradient found between monitoring wells WV Of and WV-MA-02.
|
From page 6... ...
Although the limited information available for Ward Valley suggests that some of the shallow subsurface carbonate or "calcrete" horizons are laterally continuous, and less permeable than the surrounding soil, studies from other arid regions and incomplete experimental data Tom Ward Valley indicate that the permeability of the calcrete is high enough to allow downward movement of water under conditions of low-water content and potentials, and extremely low-water fluxes. Moreover, at the Ward Valley site, both ancient buried surfaces and the modern surface of the alluvial fan have a slope of only about 2 percent, which Darcy flow calculations indicate is too low to allow significant lateral flow in the unsaturated zone.
|
From page 7... ...
It cannot be ruled out however that some portion of the around water passing beneath the proposed site -7 ~ 7 -a r - ~ may leave the Ward Valley basin. · Although, in the committee's evaluation of the pathways, four of the five postulated routes appeared to be possible, the committee judged that it would not be possible under any reasonable expectation for site characterization to either confirm, or eliminate with absolute certainty, any of the regional bedrock pathways postulated by the Wilshire group.
|
From page 8... ...
Discussion of Issue 4 Compliance and Performance Monitoring Two basic types of monitoring are proposed for Ward Valley: (~) regulatory compliance mon~tonng of the ground water to assure that contaminant releases do not exceed regulatory levels at the disposal system boundaries and (2)
|
From page 9... ...
In the opinion of the committee, the addition of these wells will provide sufficient monitoring points for ground water, and that no downgradient, offsite wells are required. Recommendations for Issue 4 Unsaturated Zone Monitoring · Although fundamental site characterization data are collected prior to the license application, it is the committee's opinion that site characterization should be continued through the operational phase.
|
From page 10... ...
to be built of natural site material and placed upsiope from the waste facility site in a chevron pattern, to provide roughness to reduce the velocity of water coming ok the fan toward the site, will likely be eroded and breached over a period of decades but will probably continue to function to provide the desired now resistance for several additional decades, and will have no impact on the stability of the site. · In the committee's opinion, concerns over possible floodwater ponding along the upstream edge of the flood protection berm and possible water seepage through the berm and into the trench area can be effectively ameliorated through easily-engineered defensive measures.
|
From page 11... ...
Breakup Berms i A series of shallow, flow breakup benns will be placed in a staggered, offset chevron pattern upsiope and west of the disposal facility primarily (~) to create sheet flow roughness to decrease sheet flow velocity near the permanent primary flood control berm and thereby reduce scour potential and (2)
|
From page 12... ...
Discussion of Issue 6 Plan to Remediate Potential Impacts The site of the proposed facility is in a section of the Moiave Desert that contains one of the largest and most robust desert tortoise populations and is considered to be a vital area for recovery of the desert tortoise. The proposal for the Ward Valley site comprises several approaches for mitigating adverse effects of site construction and operation on the local desert tortoise population.
|
From page 13... ...
S Fish and Wildlife Service on the low-Ieve} radioactive waste disposal site at Ward Valley be reinitiated, which is required by the Endangered Species Act if critical habitat is designated which may affect a prior biological opinion.
|
From page 14... ...
This in turn is likely to produce a vegetation cover gradient with the upper end of the trench caps having sparser plant cover and possibly less robust plants than the lower end. If properly planned and fillly restored according to established guidelines and expert input, the vegetation cover gradient should not cause a problem relative to soil erosion because the upper end of the trench cap will receive only rainfall and thus will not be impacted by surface flow erosion.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.