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Draft Supplemental Environmental Impact Report Page 111-26 Forward Inc.Landfill 2014 Expansion Project Surface Water and Erosion Maintenance and Monitoring Water collected in the three sedimentation basins(on the northwest side of the existing landfill, and in the southwest corner of the site,on either side of the South Branch)is sampled quarterly in accordance with the site's Storm Water Pollution Prevention Plan(SWPPP),WDRs,and Mitigation Monitoring and Reporting Program(MMRP). Leachate Control and Recovery Systems As discussed in Existing Permitted Waste Management Units and Facilities,above,the majority of the existing WMUs at the existing Forward Landfill contain blanket Leachate Collection and Recovery Systems(LCRSs). There is no LCRS underlying the northern portion of the landfill (the former Austin Road Sanitary Landfill),and portions of the eastern part of the site(original Forward Landfill). However,there is a LCRS located above the top of the former Austin Road Landfill to drain leachate from WMUs FU-03 to FU-08 that overlie the former Austin Road Landfill top deck. The LCRS design utilizes two configurations to account for the two types of slopes encountered; base grades and side slopes. On the base of the WMUs the LCRS consists of a 1-foot thick layer of granular material sloped towards a system of perforated HDPE leachate collection header pipes. The LCRS collection header pipes slope at a minimum of one percent toward the sumps. The piping and drainage layer is directly underlain by the composite lining system. A geotextile is -- used under all pipes to protect the HDPE geomembrane liner from potential abrasion caused by the pipes. The drainage layer is separated from the operations layer above by a nonwoven geotextile to prevent migration of fine-grained material into the LCRS. The LCRS design for slopes greater than 15 percent consists of a geocomposite drainage net (GDN). GDN is used due to construction and stability concerns associated with placement of granular materials on steep slopes. No collection pipes are required on the side slopes because any leachate occurring on the slope would naturally flow down slope. Leachate collected in the LCRS would flow through the drainage layer to the pipes and _ subsequently into leachate collection sumps. Submersible pumps located in each sump would pump leachate from the LCRS to lined surface ponds,from which the leachate evaporates. Three leachate evaporation impoundments are permitted at the site,of which two are constructed and are currently in use. WMU F North is located in the southwest region of the existing Forward Landfill,just north of the South Branch. It was constructed in 1999 and provides containment for leachate from the active portions of the southern WMUs. The leachate impoundment was sized -� based on actual leachate generation records from 1991 to 1997 and has a design capacity of approximately 3.5 million gallons. WMU F West is located in the northern portion of the site, directly west of WMU FU-03. It was constructed in 2003 with a design capacity of 3.4 million gallons and receives leachate from the northern waste management units. A third impoundment, WMU F South,has not yet been constructed as no waste has yet been landfilled south of the South Branch. If,during the service life of the landfill,the demand on the leachate impoundment exceeds capacity,Forward would implement an alternative leachate management plan. Leachate in excess of the impoundment's capacity would either be pumped to temporary onsite tanks,trucked for off- site disposal at the City of Stockton Municipal Utility Department wastewater treatment plant located at 2500 North Navy Drive in Stockton,or trucked to another off-site licensed Treatment and Disposal Facility. Leachate stored in the temporary on-site tanks may be released back into the impoundment at a later date.