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Earthen Materials in Surface Barriers
Pages 97-107

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From page 97...
... Design of an earthen cap to minimize percolation entails manipulating soil water storage capacity, lateral drainage, transpiration, and evaporation such that an acceptable value for percolation occurs in a worst-case design year (e.g., year when rainfall or snowfall is abnormally high and temperature and solar radiation are abnormally low)
From page 98...
... RESISTIVE BARRIlERS Principle Traditional resistive barriers are the most commonly used earthen caps today, even though their cost, performance, and durability can be poorer than other types of earthen caps. A traditional resistive cap consists of a battier layer of compacted fine-gra~ned soil and a vegetated surface layer (Figure 21.
From page 99...
... D-81 Lateral Drain Barrier Layer Adequate performance of a traditional resistive battler is predicated on the barrier layer having low saturated hydraulic conductivity. If the battier layer has low saturated hydraulic conductivity, percolation from the base of the cap is controlled by the saturated hydraulic conductivity of the barrier layer and the gradient imposed by water pending on the barrier layer.
From page 100...
... . FIGURE 4 Desiccation Crack in Cap Designed as a Resistive Barrier
From page 101...
... The resistive battier consists of 600 mm of compacted silty clay and 150 mm of vegetated silty topsoil. The test section is instrumented extensively to obtain detailed information about the water balance (Benson et al., 1994~.
From page 102...
... These caps employ the capillary barrier principle to divert infiltrating water via lateral flow while ensuring that deep percolation does not occur (Nyhan et al., 1993; Yeh et al., 19944. pi pi P 1~ 1 Fine-Grained Soil coarse-Grained Soil (a)
From page 103...
... - recommended resistive battier cap (topsoil layer, sand drainage layer, and a 600-mm-thick soil layer having saturated hydraulic conductivity less than 1 x loo m/s) , a loam capillary barrier (topsoil layer, fine sand wicking layer, grave!
From page 104...
... Low saturated hydraulic conductivity limits infiltration through the surface during rainfall or snow melt. High soil water storage capacity provides the capability to store water that does infiltrate until it can be removed by evapotransp~ration.
From page 105...
... describe the performance of a monolayer barrier proposed as a cap over contaminated soil at Rocky Mountain Arsenal in Commerce City, Colorado. The battier, which is constructed over trenches containing hazardous constituents, consists of a vegetated layer of topsoil underlain by a compacted layer of fine-grained soil (Figure 81.
From page 106...
... Currently, three designs for earthen caps are being used: resistive baITiers, capillary barriers, and monolayer barriers. Resistive barriers rely on the low saturated hydraulic conductivity of a barrier layer to limit percolation.
From page 107...
... 1993. Evaluation of Unsaturated Fluid Flow, Coastal Sage Scrub Habitat Area, Coyote Canyon Final Cover System, Orange County, California, report prepared by GeoLogic Associates for Orange County Integrated Waste Management Department.


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