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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2010-0016 -27- SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS NORTH COUNTY LANDFILL SAN JOAQUIN COUNTY <br /> <br /> Secondary Composite Liner 60-mil HDPE/GCL Foundation Layer ≥ 1’ compacted subgrade ____________________________ 1. Sump shall be equipped with an automatic pump, flow meter, and recordation device, allowing instantaneous measurement of rate and volumes removed. High and low liquid level sensors and associated alarms shall also be included in design. 2. 8 oz/yd2 non-woven fabric. 3. 12-inch HDPE riser included for leachate monitoring and removal. <br />3. The foundation layer in the above composite liner designs (D.2.a and D.2.b) shall be constructed as follows: <br />a. Project CQA shall include preparation of the foundation surface so as to minimize the risk of liner puncture and leak detection testing. In both of the above designs, the foundation layer shall consist of select fine-grained soil materials compacted as follows: <br />1) In lifts of 6 inches or less; and 2) To 90% of maximum dry density at 0 to 4% wet of optimum moisture content, in accordance with the approved CQA plan; and 3) To a minimum hydraulic conductivity of 1 x 10-5 cm/sec; or 4) In accordance with the following gradation criteria: i. A maximum size of 3/8-inch; and ii. At least 30% of the material, by dry weight, passing the No. 200 U.S. Standard sieve; and iii. A gradation series (i.e., well-graded) that is amenable to compaction. <br />b. Additionally, for the EAD (D.2.b), the subgrade for the bottom and side slopes shall be prepared in an appropriate manner using accepted engineering and construction methods so as to provide a smooth surface free from rocks, sticks, or other debris that could damage or otherwise limit the performance of the GCL. 4. The Discharger may propose changes to the liner system design prior to construction provided that approved components are not eliminated, the engineering properties of the components are not substantially reduced, and the proposed liner system results in the protection of water quality equal to or greater than the design prescribed by Title 27 and this Order. The proposed changes may be made following approval by the Executive Officer. Substantive changes to the design, including, but not necessarily limited to, changes affecting the landfill containment system; LCRS; precipitation and drainage controls; final cover; and/or slope stability shall require re-evaluation as an EAD and approval by the Board.