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Draft Environmental Impact Report Page IVY-21 Forward Inc. Landfill Expansion As described in the Project Description, state and Federal standards have been established for the siting, design, construction, operation, closure, and postclosure of Class II landfills. Similarly, the closed Class I landfill has post-closure monitoring and maintenance requirements. These standards incorporate state-of-the-art engineering requirements that are intended to reduce the risks associated with waste disposal facilities to an acceptable level. An inconsistency between the proposed project and regulations related to surface or groundwater hydrology and water quality also would have the potential to result in significant impacts. Impact F.1: Uncontrolled flooding could result during peak rainfall events and result in contamination of surface water bodies through contact between the landfill refuse and surface water. If rainwater contacts the landfill refuse and picks up dissolved contaminants and is not controlled by a drainage system it could migrate to Littlejohns Creek and flow downsream to the San Joaquin River. The applicant's geotechnical report (Geologic,2008a) states site drainage run-on and runoff after heavy rainfall periods would be channeled to on-site storm water/ sedimentation ponds. The drainage study utilizes San Joaquin County local rainfall data, and the Rational Method was used to estimate maximum potential runoff. The surface water control system and drainage control structures for the proposed project are sized to accommodate the calculated peak flows. The proposed surface water control system is designed for a 1,000-year, 24-hour storm event, and would divert run-on from properties surrounding the landfill. The following surface water management procedures are proposed as part of the project: • An updated JTD by the applicant would be completed to include a new drainage study for the proposed expansion. The geotechnical drainage study would utilize San Joaquin I County local rainfall data, and the Rational Method would be used to estimate �I maximum potential runoff. The surface water control system and drainage control structures for the proposed project would be sized to accommodate the calculated peak flows. • As part of the design plans for the proposed landfill, Forward Landfill would complete calculations of the 1000-year, 24-hour storm event peak discharges. The hydraulic and drainage study would be used to design appropriate drainage controls. Drainage controls would be designed to prevent contact between surface water and refuse. Site run-on and-run-off control facilities consist of drains and perimeter ditches that channel surface water to holding and evaporation ponds on the site. The surface-water collection drain system would be designed to divert the water to the storm water collection basin in the southwest corner of the Austin Road Landfill unit. All waste at the proposed Forward Landfill would be separated from the north and south branches of Littlejohns Creek by a levee system or other acceptable method designed to protect the site from a 100-year flood event. • The project includes channel reconfiguration and localized flood protection berms to isolate the landfill surfaces from floodwaters. i • The project design shall also include provision of replacement floodplain area and 6J storage volume in an easement along the relocated Littlejohns Creek. • The,channel and floodplain storage easement are designed to accommodate the 100- year,24-hour storm. The design would also include a three-foot freeboard.