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eoLogic Associates <br />Geologists, Hydrogeologists and Engineers <br />July 13, 2005 <br />9 Job No. 2005-082 <br />Allied Waste Industries, Inc. <br />901 Bailey Road <br />Pittsburg, California 94565 <br />Attention: Mr. Locklin Caffey <br />I To a stm Li 11 mg, 1 g 10 1 & I W-1 e 1115 11 N M M, q g M Lug-' 01 gemm <br />This report is presented as an evaluation of the performance of an alternative final cover <br />system proposed for the closure of the North and Northwest slopes of the Forward <br />Sanitary Landfill in San Joaquin County, California. The analyses presented herein are <br />submitted as a basis for agency approval of this final cover system. The analyses have <br />been completed using local climatological data, soil data specific to the existing final <br />cover soils and the potential on-site borrow source and vegetative conditions typical of <br />the natural environment adjacent to the landfill. <br />1.1 REGULATORY REQUIREMENTS <br />California Code of Regulations (CCR) Title 27 § 21090 (a) require that landfill final <br />covers be constructed according to identified minimum standards. For unlined Class III <br />landfills similar to the Forward Sanitary Landfill (FSL), the minimum regulatory <br />requirements include a two -foot thick foundation layer, a one -foot thick low -hydraulic <br />conductivity layer, and a one -foot thick vegetative layer. As prescribed, the low - <br />hydraulic conductivity layer is to consist of soils with a saturated hydraulic conductivity <br />of less than 1 x 10-6 cm/sec. <br />CCR Title 27, Section 21090 (a) allows for alternatives to this prescriptive <br />standard in stating: <br />"The Regional Water Quality Control Board (RWQCB) can allow any alternative <br />final cover design that it finds will continue to isolate the waste in the Unit from <br />precipitation and irrigation waters at least as well as would a final cover built in <br />accordance with applicable prescriptive standards under ¶(a)(1-3)." <br />In addition, under the CCR Title 27 § 20080 (e)(1) the StateWater. Resources Control <br />Board (SWRCB) requires the discharger to demonstrate that the prescriptive is not <br />feasible because it: <br />1360 Valley Vista Dr., Suite 100, Diamond Bar, CA 91765 Phone: (909) 860-3448 FAX: (909) 860-2024 <br />