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WASTE DISCHARGE REQUIREMENTS ORDER R5-2015-0058-01 -22- SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS FOOTHILL SANITARY LANDFILL, INC. FOOTHILL LANDFILL SAN JOAQUIN COUNTY Landfill 2 93. Previous WDRs Order R5-2003-0020 approved an EAD to the Title 27/Subtitle D prescriptive liner design for an MSW landfill proposed by the Discharger for the containment systems of LF-2, Module 1 and future expansion modules at the site. The approved EAD included the following elements:9 Component Base Liner Side Slopes Operations Layer 2 feet soil Filter Fabric Geotextile1 Geocomposite2 LCRS 9-inch gravel drainage layer 4-inch HDPE collection piping in drainage troughs Base Liner 60-mil HDPE3 Geosynthetic Clay Liner (GCL) Foundation Layer Prepared subgrade ≥ 1 foot Thickness not specified 1. Geotextile consists of 8 oz/yd2 non-woven fabric. 2. Geonet with above geotextile on both sides. 3. HDPE double-side textured. In authorizing the above EAD for the landfill’s containment system, previous WDRs found that the Discharger had made the requisite demonstration under Title 27, Section 20080(b) that construction of the prescriptive design was infeasible and that the proposed EAD met Title 27 performance standards. See Information Sheet. 94. The first phase of Module 1 (M-1A) was constructed in 2003 in accordance with the above EAD. M-1A consisted of a 34-acre expansion of the landfill footprint immediately south of LF-1. Excavation side slopes were graded to 1H:1V, forming the sides of native soil berms constructed around the module. The foundation layer was graded from northwest (267 feet MSL) to the southeast (225 feet MSL) at a slope of 3%. Anchor trenches were cut into the northern and southern perimeter berms to anchor the liner. 95. The second phase of Module 1 (M-1B), constructed in 2006, consisted of a northward extension of the landfill footprint over a native soil berm between LF-1 and LF-2 and the filling of wastes up against the lower slopes of unlined unit LF-1. A geomembrane barrier layer was installed in the area of overlap between the two modules as a corrective action measure to help prevent leachate and gas migration into LF-1.10 9. Under Title 27, section 20080(b), the Discharger may construct an engineered alternative to the Title 27 prescriptive standard provided that the requisite demonstration is made (e.g., that the design meets Title 27 performance standards and that compliance with the prescriptive standard is not feasible). 10.The geomembrane barrier layer was not a construction requirement because the landfill was considered a single unit under previous WDRs and therefore the overlap area did not constitute an expansion of the landfill footprint under Title 27/Subtitle D. See Finding 96.b and Title 27, section 20164.