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0 3.0 LABORATORY TESTING <br />In accordance with ASTM and other acceptable standards, the proposed on-site borrow <br />soils and the existing cover soils were tested for classification (ASTM D-2487), moisture <br />content (ASTM D-2216), gradation analysis (ASTM D-422), maximum relative density <br />and optimum moisture content (ASTM D-1557), permeability testing (ASTM D 5084) <br />and soil matric potential (ASTM D-6836). The results of the laboratory testing conducted <br />on the selected samples are summarized in Table 1, and complete test results are included <br />in Appendix B. <br />With regard to permeability, it should be noted that the bulk of the available borrow soils <br />are expected to yield a remolded saturated hydraulic conductivity of less than 1x10-6 cm/s <br />(the prescriptive standard for an unlined cell). As indicated by the testing of relatively <br />undisturbed samples of the interim cover however, it is likely that these soils will weather <br />over time to yield a long-term in-situ conductivity of greater than 1x10"6 <br />4.1 GENERAL <br />The infiltration modeling program LEACHM (Leaching Estimation and Chemistry <br />Model) was selected for the alternative final cover analyses summarized herein. <br />LEACHM is a one-dimensional finite difference computer model developed at Cornell <br />University. The model simulates water and solute transport in unsaturated or partially <br />saturated soils to a depth of about two meters. Estimates of plant growth and absorption <br />of water by plant roots are included in the model as are climatic factors such as <br />precipitation and evaporation. LEACHM is able to predict net flux through a final cover <br />soil configuration by allowing the user to stipulate laboratory determined matric <br />potential/soil moisture content relationships, bulk density/porosity relationships, and <br />saturated hydraulic conductivity values. These values are transformed in a curve fitting <br />routine to produce the air entry value and exponent ("a" and "b" coefficients) used in <br />Campbell's retentivity equation. Unsaturated hydraulic conductivity is then estimated for <br />a given soil moisture content using Campbell's conductivity relationship. After <br />calculation of soil retentivity and unsaturated hydraulic conductivity, LEACHM simulates <br />unsaturated flow through the modeled profile using Richards' equation. <br />The following sections describe the critical assumptions, variables, and input <br />requirements incorporated into the LEACHM computer analysis. Variables specified in <br />the model include the iteratively calculated transient soil water status factors, plant <br />growth, plant maturity, plant harvest variables, soil matric potential and saturated <br />hydraulic conductivity. Sample input/output files for the LEACHM program are <br />provided in Appendix C. <br />Rn <br />C. -MOS -009 ORWARnrt+arwsrdCOVEn.noam3/soos <br />Geologic Associates <br />