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Draft Environmental Impact Report Page III-17 P p g �r. Forward Inc. Landfill Expansion t facilities for the existing Forward Landfill have been designed to convey peak discharge resulting from 1,000-year,24-hour storm event runoff volumes. The storm water and drainage facilities of the proposed landfill expansion would be designed for the 1,000-year storm event. The drainage network for the completed landfill is designed to carry storm water at velocities that would minimize ditch erosion. Currently,all landfill surface water is routed to one of three sedimentation/detention basins. Two sedimentation basins are located in the southwest corner of the site,on either side of the South Branch. The basin located north of the South Branch collects runoff from the landfill area in the southern portion of the site,and the basin located south of the South Branch collects runoff from the MRF area. A third sedimentation/detention basin,located on the northwest side of the existing landfill,directly west of WMU FU-03, collects runoff from the northern portion of the landfill. For purposes of the lateral expansion, the sedimentation basin currently located in the southern portion of the site, north of the South Branch, would be relocated. New sedimentation basins would be located along the southern portion of the expansion area and in the area currently occupied by the administrative offices. The erosion control measures incorporated in the site design include the following: • Collection and control of runoff, diverting it away from highly erodible areas I ' • Construction of intermediate and final landfill slopes with drainage benches at i intervals designed to control slope runoff velocities and volumes • Hydroseeding with fast germinating drought-tolerant grass seed on intermediate surfaces that would be exposed for more than 180 days and all surfaces that are at final grade. Seeded surfaces would be watered until growth is well established. i i Soil erosion from the proposed landfill slopes was calculated to be less than the maximum allowed by the EPA for landfill final covers. The vegetative layer of the final soil cover would be seeded with native grasses to protect the upper layer of soil, and to minimize erosion. 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). r 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). t � 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 would consist of a 1-foot thick layer of granular material sloped towards a system of perforated HDPE leachate collection header t