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WASTE DISCHARGE REQUIREMENTS ORDER R5-2015-0058-01 -47- <br />SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS <br />FOOTHILL SANITARY LANDFILL, INC. <br />FOOTHILL LANDFILL <br />SAN JOAQUIN COUNTY <br /> <br />Base Liner 60-mil HDPE3 None4 <br />Geosynthetic Clay Liner (GCL)5,6 <br />Foundation Layer ≥ 1 foot prepared subgrade7 <br /> <br />1. Geotextile consists of 8 oz/yd2 non-woven fabric. <br />2. Geonet with geotextile on at least one side. <br />3. HDPE textured on at least one side. <br />4. Additional containment components (e.g., synthetic barrier layer) shall be installed if (and to the <br />extent) required under an approved corrective action program submitted under these WDRs and/or <br />separate Central Valley Water Board order (e.g., CAO R5-2004-0706). <br />5. GCL shall exhibit appropriate strength characteristics (hydrated) to accommodate stresses <br />associated with specific landfill design parameters, with particular attention to interface, long-term <br />creep, shear, and bearing capacity. <br />6. May alternatively be constructed with a Title 27 prescriptive clay liner. See Title 27, section <br />20330(a). <br />7. See Construction Specification D.2. <br /> <br />2. The foundation layer in the above composite liner design (D.1) shall be <br />constructed as follows: <br />a. Project CQA shall include both preparation of the foundation surface so as to <br />minimize the risk of liner puncture, and leak detection testing. The foundation <br />layer shall consist of select fine-grained soil materials compacted as follows: <br />1) In lifts of 6 inches or less; and <br />2) To at least 90% of maximum dry density per moisture content specification <br />in approved CQA plan; and <br />3) To a minimum hydraulic conductivity of 1 x 10-5 cm/sec; or <br />4) In accordance with the following gradation criteria: <br />i. A maximum size of 3/8-inch; and <br />ii. At least 30% of the material, by dry weight, passing the No. 200 U.S. <br />Standard sieve. <br />b. The subgrade for the bottom and side slopes (including LF-1/LF-2 interface <br />areas) shall be prepared in an appropriate manner using accepted <br />engineering and construction methods so as to provide a smooth surface free <br />from rocks, sticks, or other debris that could damage or otherwise limit the <br />performance of the GCL. <br />Landfill LCRS <br />3. The LCRS for LF-2 expansion modules shall, at a minimum, be constructed in <br />accordance with the following, from top to bottom: <br />a. Blanket Drainage Layer – <br />1) Minimum 9-inches thick layer of sufficiently rounded or cushioned <br />drainage gravel over base liner <br />2) Geocomposite (or equivalent combination of geonet and filter fabric) over <br />side slopes, including LF-1/LF-2 interface areas. <br />b. Collection Piping <br />1) Perforated HDPE laterals installed in collection troughs (or directly on <br />base liner) and plumbed to header pipe(s) or directly to an LCRS sump <br />(e.g., depending on module design/geometry). Laterals shall be equipped