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• <br />Geo-Loqk <br />A S S 0 C I A T E 5 <br />May 08, 2018 <br />GLA P/N: AU17.1254 <br />Mr. Taj Bahadori <br />San Joaquin County Public Works Department <br />Solid Waste Division <br />1810 Hazelton Avenue <br />Stockton, California 95205 <br />REQUEST FOR ALTERNATIVE LEACHATE COLLECTION AND REMOVAL SYSTEM (LCRS) <br />DRAINAGE LAYER MATERIAL— FOOTHILL SANITARY LANDFILL <br />Mr. Bahadori: <br />Per your request, Geo -Logic Associates (GLA) has reviewed the feasibility of using an alternative <br />material for the Leachate Collection and Removal System (LCRS) drainage layer at the base of <br />the Area 2B expansion of the Foothill Sanitary Landfill (FSL). GLA understands that the <br />alternative LCRS drainage layer is of interest to the County due to the limited availability of <br />locally derived gravel drainage media meeting common LCRS requirements. Due to the limited <br />nature of gravel sources, significant haul distances are necessary to obtain the material, <br />resulting in increased LCRS construction costs and environmental impacts from material <br />haulage. A Geocomposite Drainage Net (GDN) was reviewed as an alternative to the 0.75 -foot - <br />thick gravel drainage layer (GDL) that was used for previous module Area 2A and that is <br />discussed in the FSL's current Waste Discharge Requirements Order Number R5-2015-0058 <br />(WDR). <br />The previous LCRS was designed to be constructed, operated, and maintained to collect twice <br />the maximum anticipated daily volume of leachate from the FSL as required by the California <br />Code of Regulations (CCR) Title 27 (Section 20340[b]), and by the FSL's WDRs. To meet CCR Title <br />27 and WDR requirements, the previous LCRS design for the FSL was developed consisting of a <br />ridge and valley system having 6 -inch diameter perforated high density polyethylene (HDPE) <br />pipes placed within a 0.75 -foot -thick granular drainage layer. Furthermore, the LCRS is sloped <br />on the floor to convey leachate by gravity to the LCRS sump located at the eastern side of the <br />module. In addition to providing adequate drainage and limiting hydraulic head on the liner, the <br />previous LCRS was designed to resist collapse under the weight of the final waste mass resulting <br />from the landfill configuration after final closure. <br />GLA has considered the above described LCRS design and evaluated the feasibility of using an <br />engineered alternative design (EAD) in the form of a GDN drainage layer with respect to <br />structural and hydraulic characteristics. Specifically, GLA has evaluated an alternative LCRS <br />design comprised of a GDN placed directly above the 60 -mil HDPE barrier layer that drains via <br />ridge and valley floor grading to 6 -inch HDPE pipes located in gravel filled trenches below the <br />143E Spring Hill Drive • Grass Valley, California 95945 • T 530.272.2448 • F 530.272.8533 • www.geo-logic.com <br />