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0 5.2 DESIGN PLANS 5.2.1 Previous Designs • The design service area for this facility was the northern portion of San Joaquin County. Module 1 (previously designated "Modules 1 and 2") was constructed in 1991. This module is provided with a 60 -mil HDPE liner installed over a 6 -inch (minimum) thick layer of compacted native soil. The side slopes are provided with a non -woven geofabric over HDPE liner. The base is provided with a geonet drainage layer for the collection of leachate. An operations soil layer, not less than 2 feet thick, was placed on the side -slopes and base prior to the placement of refuse. Leachate drains through the geonet to shallow gravel -filled "V" ditches which drain the leachate through pipes out a sump at the south east corner of Module 1. • Module 3 was constructed in 1995 in conformance to RCRA Subtitle D and CCR Title 27 standards. The base of this module is covered with a composite liner consisting of a geosynthetic liner (GCL) under a 60 -mil HDPE membrane. The GCL extends under the HDPE approximately 6 feet up the side -slopes. The side sloes are protected by 80 -mil HDPE is over a minimum 6 -inch layer of compacted soil. Base and side -slopes are provided with a geonet drain layer. An operations soil layer, not less than 2 feet thick, was placed over the geonet prior to the placement of refuse. Leachate drains through geonet to shallow "V" trenches, then through pipes to a leachate sump. The interface between Modules 2 and 3 is composed of an anchor trench/berm, raised approximately three feet above the surrounding surfaces. • Module 4 was constructed in 2003, also in conformance to RCRA Subtitle D and CCR Title 27 standards. This module is lined with a composite liner comprised of 60 -mil HDPE over GCL. On the side -slopes, the composite liner is placed on a 6 -inch thick layer of prepared soil, and is overlaid by a geonet drain layer. At the base, the composite liner is placed over a one -foot thick layer of soil with not less than 30% passing 200 sieve, compacted to not less than 90% relative density. A 9 -inch layer of pea gravel is installed above the bas liner, over which filter fabric and not less than two feet of operations soil is placed. In addition, the first two feet of refuse placed on the operations layer is "packer waste" or other material free of large objects that could penetrate through the operations layer and the liner beneath. 0 North County RC&SL Page 24 of 69 Public Works/Solid Waste Joint Technical Document County of San Joaquin — February 10, 2010