Barrier Technologies for Environmental Management Summary of a Workshop (1997) / Chapter Skim
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Development and Testing of Permanent Isolation Surface Barriers at the Hanford Site
Development and Testing of Permanent Isolation Surface Barriers at the Hanford Site
Pages 21-40
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From page 21... ...
A prototype barrier, incorporating all essential elements of a long-term surface barrier, was constructed at the Hanford Site in 1994 and is currently being monitored. This paper provides an overview of the barrier development work being conducted at the Hanford Site and the functional performance of the permanent isolation surface barrier.
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From page 22... ...
These major barrier development task groups are water infiltration control, biointrusion control, erosion/deposition control, physical stability testing, human interference control. barrier construction materials procurement, prototype barrier designs and testing, mode!
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From page 23... ...
1 - 1 Resource Conservation and Recovery _ Act Equivalency Technology Integration and Transfer ProJect Management ~1 Model Appilcatlons ~_ and Validation ~/ Final i ~- I ~ Design Long-Term Cllmate Change Effects 1 ' -- - 1 Natural Ba rier ~ / Analogs ~/ .~ \ \rF 'hysical \ Stability \ Testing Prototype Barrier Designs and Testing FIGURE 1 Barrier Development Tasks. Barrier Construction Materials Procurement Human Interference Control FllNCTIONAL REQUIREMENTS FOR THE BARRIER .
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From page 24... ...
Erosion-related problems could provide a direct pathway for contaminant transport if the erosive forces are strong enough to remove the surface soils and expose the buried wastes to the accessible environment. A more probable scenario is for wind and water erosion to reduce the thickness of soils overlying a waste zone so another transport pathway (i.e., water infiltrations becomes a more serious concern.
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From page 25... ...
The diffusion of noxious gases from the waste zone to the Permanent isolation surface barriers have been proposed to protect wastes, disposed of in place, from the transport pathways identified. Surface markers, used to inform future generations of the nature and hazards of the buried wastes, are being considered for placement around the periphery of the waste sites.
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From page 26... ...
The amount of water available depends on the climate. Because of the long time frame during which permanent isolation surface barriers must function (1,000+ years)
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From page 27... ...
projection has been used since November 1990 as the upper bound when applying supplemental precipitation to field test plots. Designing a Barrier for Drainage and Percolation Control Based on the climatological conditions and projections discussed previously, three methods are described for controlling the Infiltration and percolation of water through a protective baITier: (~)
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From page 28... ...
In these circumstances, a climax community of vegetation may not reestablish itself on the barrier surface for a long time (Waugh et al., 1994; Link et al., 19951. Although the presence of vegetation on the barrier surface is ideal, the results of lysimeter tests, presented in the following paragraphs, provide interesting evidence that the capillary barrier concept performs effectively, even in the absence of vegetation.
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From page 29... ...
~1. .1 ~ ~ ~,1 ~q ~-~'u · ~ ~ ,,, 1 'am FIGURE 4 The Field Lysimeter Test Facility: Schematic View.
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From page 30... ...
Vegetated battier systems are able to accommodate even greater amounts of precipitation because of the water extraction capabilities of plants, thereby providing increased storage capacity. Low-Permeability Layers The basic premise of the capillary barrier concept is that most, if not all, of the meteoric water that infiltrates the barrier surface can be returned to the atmosphere by surface evaporation and plant transpiration.
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From page 31... ...
The lack of significant water infiltration at depth and the overall water loss in the lysimeter plots occurred despite the following worst-case conditions: .
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FIGURE 5 Animal intrusion Lysimeter Facility: Experimental Design. Other observations were made with the large-mammal burrows.
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From page 33... ...
The presence of vegetation on the barrier surface will reduce the amount of fine soil lost from the barrier by wind and water erosion significantly. However, to protect the barrier surface during periods when the vegetative cover is disturbed by range fires, drought, disease, or some other phenomenon, surface gravels will be admixed into the surface of the protective barrier.
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From page 34... ...
Because of these results, the use of admix gravels rather than gravel mulches is recommended to avoid water infiltration. ASSESSING WATER INFILTRATION T~OUGII TlIE PROTOTYPE BARRIER The prototype surface barrier constructed at the Hanford Site in 1994 is shown in cross section and plan view in Figure 3.
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From page 35... ...
Bimodal Gravel V FIGURE 6 Small-Tube Lysimeter Facility: Experimental Design. Treatment Combinations ~3 Gravel Admix Dune Sand Surface Gravel McGee Soil No.
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From page 36... ...
1 1 1 1 1 1 1 1 1 S O N D J F M A M J J A S O N D J F M A M J J A S O 1994 1995 1996 Time (mo) FIGURE7 Temporal Variation ~n Soil-Water Storage at the Prototype Barr~er S~nce September 1994.
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From page 37... ...
O N- D 1996 F M A M J J A S O FIGURE 9 Monthly Drainage From Sideslope at the Prototype Barrier Since September 1994.
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From page 38... ...
Because only a finite amount of time exists to test a battier that is intended to function for a minimum of 1,000 years, the testing program has been designed to "stress" the prototype so that barrier performance can be determined within a reasonable hme frame. Continued monitoring of prototype barrier performance for extended periods is desirable because the succession of vegetation types, the full development of root profiles, and the natural colonization of the barrier surface by burrowing animals will occur over a longer time period.
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From page 39... ...
1993. Water Erosion Field Tests for Hanford Protective Barriers: FY 1992 Status Report, PNL-8949, Pacific Northwest Laboratory, Richiand, Washington.
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From page 40... ...
1993. Permanent Isolation Surface Barner Development Plan, WHC-EP-0673, Westinghouse Hanford Company, Richiand, Washington.
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