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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:\PROJECTS\Allied Waste\Forward\Reference Files Prior JTD\June 05 Stage IA Partial FCPCMP\FL-sec3.doc: 6/16/2008 <br />