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' The perimeter side slopes will be excavated at 3: 1 (horizontal to ver- tical ) down to an average excavation depth of 30 feet. Based on the ' hydrogeologic investigations (see Appendix A) , these base grades will be from 96 to more than 118 feet above existing ground-water eleva- tions. The base of excavation will be sloped towards the perimeter at 2 percent minimum with a cross-slope of 2 percent into the center of ' each module. A temporary runoff containment sump outside the limits of the active module will be excavated to collect runoff from within ' the active fill and excavation modules. Based on the proposed excavation grades, the total of approximately ' 9,000,000 cubic yards of soil far exceeds the estimated soil needs for landfill operation and final soil cover. However, the additional ex- cavation will provide greater volume for refuse filling, thus extend- ing the service life of the site. Excess excavated soils will be dis- posed of off site, at areas designated by the County, or sold to pro- spective buyers. ' 4.3.2 Earthfill ' Earthfill will be required at the landfill for various design features such as perimeter berms, foundations for access roads, and drainage ' facilities over refuse fill . Areas to receive earthfill will be stripped of vegetation and topsoil , scarified, and compacted before placing the initial layer of earthfill . Earthfill will then be placed by spreading the specified soil in uniform layers not over 8 inches ' thick. Each soil layer will be watered or dried as needed to bring the soil to the specified moisture content and compacted with suitable equipment to at least 90 percent relative compaction (ASTM Test Desig- nation D1557-78) . ' 4.3.3 Stockpile and Screening Berms ' Selective stockpiling of excavated soils will be necessary for later use as cover material . A screening berm north of the landfill limits ' PJ9 9390209A.00D 14 ' Emon Associates