CORRESPONDENCE_2005-2006 - Laserfiche WebLink

Home Browse Search

incorporated such that seepage is minimized, the factor of safety of the long-term partial cover was estimated to be 1.9, which is greater than the minimum required factor of safety of 1.5. 3.3. Borrow Source Characterization and Volume Estimation Soil used for construction of both the intermediate cover and partial cover on Module "I" will come from an existing borrow area immediately south of Module 1 (Drawing C-1). Two soil samples were collected from the borrow area, (BA -1 and BA -2). These samples were tested for particle size distribution, plasticity index, moisture -density relationship, hydraulic conductivity (remolded to 80%, 85%, and 90% relative compaction), and agricultural suitability. These test results are contained in the Kleinfelder report "Landfill Closure Method Selection Report, Foothill Sanitary Landfill, San Joaquin County, California" dated September 21, 2004. Figure 4-1 of that report shows the footprint of the borrow area and the locations of samples BA -1 and BA -2. Appendix A contains the soil sample analytical results. No test pits were placed at the top of Module "I" (partial final closure area) to assess the thickness of the existing intermediate cover. Test Pits S1 through S11, located on the side slopes of Module "I", showed thickness of the intermediate cover to range from 13 to 38 inches thick. We do not expect the intermediate cover thickness in the partial final closure area to differ a great deal from these measurements. We therefore anticipate that no additional soil will need be placed to meet the intermediate cover thickness requirement of one foot. The partial cover area of Module "I" (that area within the footprint of Module "I" not included in the partial final closure area) is approximately 67.3 acres. Six of the eleven soil test pits (S1 through S11) did not meet the two foot thick standard for partial cover (with few exceptions the slopes of Module "I" are 4:1 which calls for a two -foot -thick partial cover). The average thickness of these six measurements is 18 inches. For the purpose of estimating the amount of borrow soil necessary to complete the partial cover on Module "I", we will assume that 6/11 the of 67.3 acre area will require an additional six inches (24 inches minus 18 inches). This equates to approximately 30,000 in-place cubic yards of soil. 47717/SAC4R475 Page 11 of 19 Revised May 31, 2005 Copyright 2004 Kleinfelder, Inc. Partial Cover, Intermediate Cover and Drainage and Erosion Control Plan Foothill Sanitary Landfill