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