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0 <br />4.2.3 SOIL COVER CHARACTERISTICS <br />For each node or interval in the defined profile, LEACHM requires input of <br />specific soil properties including: remolded dry bulk density; initial matric <br />potential and soil moisture content; Campbell's "a" and "b" coefficients <br />(Campbell, G.S., 1974), and saturated hydraulic conductivity. Porosity is then <br />calculated as a function of the stipulated specific gravity of the soils and their <br />remolded dry bulk density. <br />Prior to initiation of modeling, the existing cover and the proposed borrow source <br />soils were tested for grain size (ASTM D-422), maximum density/optimum <br />moisture (ASTM D-1557), hydraulic conductivity (ASTM D 5084), and matric <br />potential testing (ASTM D-6836) (Table 1). Table 2 lists the soil characteristics <br />actually incorporated in modeling. It should be noted that for modeling purposes, <br />the soil characteristics of a long-term weathered soil profile similar to the existing <br />interim cover were utilized. Campbell's "a" and "b" coefficients were calculated <br />using the LEACHM RETFIT program and are based on soil grain size <br />distribution, bulk density, matric potentials and hydraulic conductivity. <br />TABLE 2- SOILS ENGINEERING PROPERTIES USED FOR MODELING <br />Soil Properties <br />Alternative Final Cover <br />Mixture at 10% <br />Compacted Relative Density <br />90% <br />Sat. Permeability cm/sec degraded on-site soils <br />3.30 x 10'' <br />Optimum Moisture Content <br />16.8 <br />Dry Density (PCF) <br />99.5 <br />Liquid Limit <br />NA <br />Plasticity Index <br />NA <br />< #200 Sieve <br />76 <br /><5 Micron (%) <br />30 <br />U.S.C.S. Classification <br />CL <br />Remolded Bulk Dry Density cm) <br />1.56 <br />Cam bell's A Coefficient <br />-4.89 <br />Campbell's B Coefficient <br />8.403 <br />4.2.4 CLIMATIC CONDITIONS <br />Precipitation - Another critical element in modeling cover performance using <br />LEACHM involves identification of total daily precipitation, as well as the time <br />and rate of water application. For each rain event, LEACHM calculates the <br />maximum time period allowed for infiltration as the specified quantity of water to <br />be applied divided by the application rate. Water, which has not entered the soil <br />profile at the end of the application period, is assigned to an excess runoff term <br />and included in the mass balance calculations. The matric potential of the soil and <br />isthe unsaturated hydraulic conductivity of the soil thus limit infiltration into the <br />5a <br />C:0003-03AEDOM HILL ALTERNATIVE COVER.D006/16/2005 <br />Geologic Associates <br />