Long-Term Institutional Management of U.S. Department of Energy Legacy Waste Sites (2000) / Chapter Skim
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4 Contaminant Isolation
4 Contaminant Isolation
Pages 35-45
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From page 35... ...
Contaminant isolation measures consist of engineered barriers, but also include groundwater pumping (hydraulic barriers) and waste stabilization approaches.
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From page 36... ...
Surface barriers typically have multiple layers, with natural and synthetic materials of differing sizes and composition chosen to stabilize the barrier, prevent intrusion by animals and plants, limit movement of wastes, prevent infiltration of water into the waste deposit, and provide a mechanism to slow the release of radioactive or toxic gases. Vegetation is often planted to stabilize the top layer of the barrier, enhance evapotranspiration, and minimize water infiltration through the barrier; in some cases, however, vegetation may increase infiltration by slowing runoff.
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From page 38... ...
and changes over time that may result in the presence of difficult-todetect preferred pathways for migration. The geological repositories for transuranic waste at the Waste Isolation Pilot Plant in Carlsbad, New Mexico, and the proposed geological repository for commercial spent nuclear fuel and high-level waste at Yucca Mountain, Nevada, both depend on engineered barriers to contain the waste in addition to the attributes of their natural geological barriers.
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From page 39... ...
These physical measurement techniques include groundwater monitoring (probably the most common) , vadose zone monitoring, and cover and barrier monitoring (usually some form of vadose zone monitoring, but this can also include physical inspection)
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From page 40... ...
CHARACTERISTICS OF IDEAL CONTAMINANT ISOLATION MEASURES Much has been written about the ability of engineered barriers and waste stabilization measures to last for the required time period necessary to manage the risk associated with leaving wastes in place. It is difficult to project limited performance data that exist much beyond a few hundred years, and even these time periods are very controversial.
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From page 41... ...
These measures are critical to success since the best-designed barrier can, and most probably will, fail if the installation of the system is compromised. CONSTRAINTS AND LIMITATIONS Engineered barriers and waste stabilization approaches, while potentially providing solutions to some of the most difficult waste management problems, are not without potential shortcomings.
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From page 42... ...
. In either case, the waste stabilization designer should take due account of the state of knowledge and uncertainties in waste isolation performance.
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From page 44... ...
Contaminant isolation systems should incorporate an effective means of performance monitoring as close to the waste and contaminated soils as possible without compromising system integrity. Monitoring within the containment system will provide useful information to vadose zone and groundwater monitoring and improve the ability to provide an early warning of potential failure.
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From page 45... ...
Recently, some limited funding has been made available. While, the DOE should be commended for initiating the Hanford Barrier prototype research (and other similar efforts, such as research appropriate to caps for waste sites in humid eastern U.S.
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