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