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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2010-0016 -13- <br />SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS <br />NORTH COUNTY LANDFILL <br />SAN JOAQUIN COUNTY <br /> <br /> <br />Title 27 standards (56.2 gal/min and 145.8 gal/min, equal to twice the computed <br />anticipated peak leachate flow rates). The results of site-specific unsaturated zone <br />modeling (using V-Leach software) based on the above data indicated <br />concentrations in groundwater below laboratory detection limits (i.e., < 1.0 μg/L) for <br />all modeled constituents after 100 years. <br /> <br />51. Previous WDRs Order No. R5-2002-0219 approved the above EAD for Module 4 <br />and future modules. Module 4 was constructed in 2004 consistent with the <br />approved EAD and LCRS design. Construction of the module was documented in <br />the November 2003 report Final Construction Quality Assurance Report for Module <br />4 at the North County Recycling Center and Sanitary Landfill, prepared by Vector <br />Engineering, Inc. <br />Grading and Drainage <br />52. Modules 1 through 4 included the following grading features: <br />a. 3H:1V interior excavation slopes; <br />b. 3H:1V exterior slopes; <br />c. Side slope benching every 50 vertical feet (20-foot wide benches). <br /> <br />53. Precipitation and drainage controls installed on the modules included: <br />a. Top decks graded at 5% minimum for drainage. <br />b. Soil berms along top deck perimeter to direct runoff to corner drop inlets. <br />c. Overside (O/S) drains to capture top deck and side slope bench runoff. <br />d. Side slope benches graded at 2% with central “V” drains to intercept and <br />convey runoff to O/S drains. <br />e. Soil berms and outboard ditch within 100-foot setback area along east, west, <br />and south site perimeter to divert run-on and convey runoff to natural drains. <br /> <br />54. Runoff from the landfill is handled as follows: <br />a. Inactive modules (i.e., M1, northern portion of M3) - runoff directed east into <br />ISB ditch system. <br />b. Active modules (i.e., M4, southern portion of M3) - runoff directed south to <br />temporary pond in future Module 5 and 6 excavation areas. <br />c. Future Module 5 and 6 areas - water from excavation area periodically <br />pumped out to ditch that flows to ISB. <br />d. Future Modules 7 through 11 areas – Runoff from these areas either flows <br />directly to the ISB ditch system, or collects in low areas and is pumped into the <br />ISB ditch system as part of site maintenance. The ISB ditch system drains to <br />ISB. <br />