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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2010-0016 -4- <br />SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS <br />NORTH COUNTY LANDFILL <br />SAN JOAQUIN COUNTY <br /> <br /> <br />15. The Water Quality Control Plan for the Sacramento River and San Joaquin River <br />Basins, Fourth Edition (hereafter Basin Plan) designates beneficial uses; <br />establishes water quality objectives; contains implementation plans and policies for <br />protecting waters of the basin; and incorporates by reference, plans and policies <br />adopted by the State Water Resources Control Board. <br />16. The beneficial uses of the San Joaquin River (between Sack Dam and the mouth <br />of the Merced River) are municipal and domestic supply; agricultural supply; <br />industrial process supply; water contact recreation; non-contact water recreation; <br />warm freshwater habitat; migration of aquatic organisms; spawning, reproduction <br />and/or early development; and wildlife habitat. <br /> <br />17. The site receives an average of 16.5 inches per year of precipitation as determined <br />from Rainfall Depth Duration Frequency data provided by the State Department of <br />Water Resources for the Linn Ranch Station about two miles north of the site. The <br />100-year, 24-hour precipitation event for this station is 3.3 inches. The estimated <br />mean Class A pan evaporation rate is about 65 inches per year. <br /> <br />18. Storm water run-on is diverted around the site by means of a perimeter berm and <br />outboard ditch within a 100-foot setback from the site boundary. Some landfill <br />runoff is also captured in the ditch. Storm water discharge locations at the site <br />include two outfalls from the landfill perimeter ditch to the wetlands mitigation area <br />and (via culvert) South Paddy Creek, one on the eastern side of the site near the <br />NE corner of future Module 11, and the other on the western side of the site near <br />the NW corner of existing Module 1. Two other (inactive) culverts along the <br />perimeter ditch are planned as future storm water discharge locations as the <br />landfill is developed. See Attachment B: Site Map. Storm water discharges to <br />South Paddy Creek are monitored under the General Industrial Storm Water <br />Permit. <br /> <br />19. Runoff from existing landfill modules and undeveloped areas of the unit is directed <br />via onsite ditches to an interim sedimentation basin (ISB) in the northeast part of <br />the site. Water collected in module excavation areas and other low spots is <br />pumped into ISB drainage system. See Finding 54. The ISB includes an overflow <br />pipe that, during periods of heavy precipitation, discharges via culvert to the <br />outboard drainage ditch. The remaining water in the ISB dissipates through <br />percolation, evaporation, and/or use in site operations (e.g., dust control). <br /> <br />20. All landfill drainage facilities, including overside drains, perimeter ditches, culverts, <br />and the ISB were designed to handle a 24-hour, 100-year storm event. See <br />Finding 53.