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5.3.4.3 SETTLEMENT OF NEW WASTES <br /> As shown in Appendix F, the refuse settlement analyses that were completed by <br /> R. W. Beck conservatively assumed that refuse will settle approximately 25% <br /> over a 30-year period, and that settlement during the operating life of the landfill <br /> can be disregarded. Since positive drainage on the finished final cover surface <br /> must be assured, the critical area for analysis was assumed to be the area of <br /> minimum (5%) grades near the center of the landfill where the depth of new <br /> refuse will be thickest. <br /> Assuming a uniform settlement of 25% of all new wastes, the analyses indicate <br /> that the 5% final cover gradient could be reduced to approximately 3.75%. <br /> Using a grid approach and assigning a random settlement value between 22% <br /> and 28%, Beck's analyses also considered differential settlement of waste <br /> materials and concluded that final grades could range from 1% to 6%, but that <br /> positive drainage would have to be maintained. <br /> Assuming the presence of a large (3 ft. x 3 ft. x 6 ft.) void beneath a 5% landfill <br /> slope, Beck's calculations indicate that ponding conditions could exist if the void <br /> is within 10 feet of the final cover. The calculations also indicate that the <br /> geomembrane could be endangered if the void exists within 3 feet of the final <br /> cover. In order to minimize this potential, load checks and waste disposal <br /> inspections will be employed to verify that large, void-promoting decomposable <br /> materials are not disposed within 10 feet of final landfill grades. <br /> 5.3.4.4 SETTLEMENT OF EXISTING REFUSE <br /> R.W. Beck (1995) calculated that the refuse within the existing Austin Road <br /> Landfill could settle as much as 2 to 4 feet under the anticipated new refuse <br /> loads. However, since the planned landfill expansion grades will mimic the <br /> existing grades, the differential settlement of existing refuse was calculated to be <br /> minimal, resulting in a differential final cover grade that ranges from 4.9% to <br /> 5.6%. Since this existing and planned configuration exists at the existing <br /> Forward Landfill, this conclusion is also considered applicable at that location. <br /> Based on this evaluation, the overall strain on the liner system associated with <br /> differential settlement of the underlying existing refuse, is anticipated to be <br /> negligible. <br /> Forward Landfill)TD 5-19 <br /> L\Allied\2000.193\Reports\ITD-PC PCMP702:Sec-5.0:5/24/02 <br /> Revision 1:07/16/02 <br /> BRYAN A.STIRRAT 6 ASSOCIATES <br />