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s�S <br />GeoLogic Associates <br />Geologists, Hydrogeologists and Engineers <br />Allied Waste Industries, Inc. <br />901 Bailey Road <br />Pittsburg, California 94565 <br />Attention: Mr. Locklin Caffey <br />Ilii► � � Z• I�Y��7�1 <br />June 16, 2005 <br />Job No. 2005-082 <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 />0 1.1 REGULATORY REQUIREMENTS <br />U <br />California Code of Regulations (CCR) Title 27 § 21090 (a) require that landfill <br />final covers be constructed according to identified minimum standards. For <br />unlined Class III landfills similar to the Forward Sanitary Landfill (FSL), the <br />minimum regulatory requirements include a two -foot thick foundation layer, a <br />one -foot thick low -hydraulic conductivity layer, and a one -foot thick vegetative <br />layer. As prescribed, the low -hydraulic conductivity layer is to consist of soils <br />with a saturated hydraulic conductivity of less than 1 x 10-6 cm/sec. <br />CCR Title 27, Section 21090 (a) allows for alternatives to this <br />prescriptive standard in stating: <br />"The Regional Water Quality Control Board (RWQCB) can allow any <br />alternative final cover design that it finds will continue to isolate the waste <br />in the Unit from precipitation and irrigation waters at least as well as <br />would a final cover built in accordance with applicable prescriptive <br />standards under ¶(a)(1-3)." <br />1360 Valley Vista Dr., Suite 100, Diamond Bar, CA 91765 Phone: (909) 860-3448 FAX: (909) 860-2024 <br />