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and minimize the effects of settlement. Perimeter maintenance and deck <br /> access roads are also designed to provide for maintenance of the final cover <br /> and environmental control systems throughout the post-closure maintenance <br /> period. <br /> The final grading plan (Drawing Sheets 3, 4, 5, 6 and 7) presents the landfill <br /> configuration after closure of Stage IA. The final slopes of Stage IA are <br /> designed at maximum grades of 3:1 (horizontal to vertical) or flatter with <br /> exception of the bench which is set at a maximum of a 50-foot interval with <br /> 2:1 slope as shown on Detail 5 on Drawing Sheet D-1. The final grading <br /> configuration was designed by a registered civil engineer in accordance with <br /> 27 CCR, Section 21090 (b)(1)(C). <br /> In addition to prevent any future inundation of the landfill from the adjacent <br /> creek during peak storm events, a flood protection berm/perimeter road <br /> improvement is proposed. Soil will be placed and compacted along a portion <br /> of the toe of the west facing slope of the Austin Unit (see Detail 2 of Drawing <br /> Sheet D-2). The objective of this engineering fill will be to build up the grade <br /> of the perimeter road to elevation above a 100-year flood event. Forward <br /> Landfill Inc. will monitor this area for performance and any excess erosion <br /> during future storm events. <br /> 3.4 LANDFILL SETTLEMENT <br /> 3.4.1 SETTLEMENT ANALYSIS <br /> Settlement analyses were completed to evaluate how the Forward Landfill <br /> containment system will respond through time as refuse decomposes and is <br /> mechanically compressed. These analyses considered the consolidation <br /> potential of native subgrade soils as well as the settlement potential of both <br /> existing and future refuse materials. These analyses are included in <br /> Appendix B. <br /> The results of the settlement analyses indicate that the subgrade soils could <br /> consolidate up to 2 feet in response to maximum refuse loads, but that the <br /> differential settlement of subgrade soils across the planned refuse footprint <br /> would be relatively minor (0.36%). While the potential for existing refuse to <br /> settle continues to exist, since the existing landfill configuration mimics the <br /> Forward Landfill PFCPCMP 3-7 <br /> Z:\PROJECTSWIIied Waste\Forward\Reference Files Prior JTD\June 05 Stage IA Partial FCPCMP\FL-sec3.doc:6/16/2008 <br />