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FORWARD LANDFILL NON-WATER CORRECTIVE ACTION PLAN 3.3 SURFACE WATER CONTROLS Surface water control includes protection of the landfill from surface water run-on and flood influence by Littlejohns Creek, as well as proper management of surface water run-off from the landfill areas. The drainage control facilities include a network of top deck diversion berms and inlets, down drains, perimeter channels and bench drains for managing surface water run-off. A brief description of the drainage facilities are discussed in the following sections. Permanent storm water run-off and drainage control facilities on site were designed to carry the peak discharge resulting from a 1,000-year, 24-hour storm event, as required by 27 CCR, Section 20320 for a Class II waste management unit. This design storm rainfall intensity used in the approved closure plan was 4.53 inches of precipitation. The drainage network for the completed landfill is designed to carry storm water at velocities that will control run-off and minimize erosion. Forward Landfill's surface water control plan consists of an integrated system of bench ditches,perimeter channels, top deck perimeter berms, and storm water sedimentation. The final landfill grades are designed so that surface water will run-off the landfill via sheet flow until intercepted by a deck berm or bench ditch. The bench ditches subsequently drain toward trapezoidal hardscape down drains or corrugated steel pipes, which discharge to perimeter channels. Finally, the perimeter channels drain to a stormwater sedimentation basin. ® All landfill surface water is routed to one of three sedimentation basins. The sedimentation basins for Forward are located in the southwest corner of the site, on either side of the South Fork of South Littlejohns Creek. The sedimentation basin for the former Austin Road Landfill is located southwest of the facility. Water collected in the sedimentation ponds is sampled in accordance with the site's Stormwater Pollution Prevention Plan(SWPPP)before it is discharged to the North or South Forks of South Littlejohns Creek. Proposed landfill slopes for the Forward Landfill were evaluated using the Universal Soil Loss Equation(USLE). The evaluation method determines the potential for soil erosion based on the rainfall and run-off factor, the soil erodibility factor, the topographic factor derived from the slope gradient and length, the cover and management factor, and the support practice factor. The evaluation indicates that the average soil loss will be approximately 1 ton per acre per year for each area evaluated, which is below the two tons per acre per year industry standard maximum soil loss. The vegetative layer of the final soil cover will be seeded with native grasses to protect the upper layer of soil, and to minimize erosion. M:\2011-012MWFA REPORT.DOCX 7 Geo-Logic Associates