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Non-Water Release Corrective Action Plan Corral Hollow Sanitary Landfill • 4.4 FLOODING IMPACTS CalRecycle's BMPs require evaluation of the landfill in relation to the 500-year flood zone, shown as Zone C or X (unshaded area) on a flood map, if available. If the 500-year flood zone covers the refuse disposal area, the evaluation should analyze the predicted elevation of the flood waters to the landfill perimeter. If the predicted elevation covers the landfill, the flood event should be analyzed and assessed for potential erosion and saturation of the landfill due to the force of moving or standing water. Flooding can be caused by storms, heavy rains, changes in the landscape due to development, or failure of engineered flood control systems such as levees or dams. The BMP for the flood as a casual event states: • Flooding is not considered a reasonably foreseeable casual event if the landfill is not located in the 500-year flood zone. • For the purposes of determining corrective action, any landfill located within the 500-year flood zone needs to assess the potential damage resulting from the 500-year flood. The CHSL is located adjacent to Corral Hollow Creek. Based on the Federal Emergency • Management Agency (FEMA) Flood Insurance Rate Map (FIRM) for the San Joaquin County, the CHSL is located within the FIRM Panel: 06077CO74OF (see Appendix D). From the FEMA Flood Zone Designations section, the landfill is located within "Zone X, shaded" (see definition in Appendix D), which are areas of a 500-year flood or 100-year flood with average depths of less than 1-foot are possible. The County evaluated the landfill in relation to the most current FEMA flood plain map in November 2012. This evaluation indicated that the landfill is outside of the 100-year flood plain. However, the limits of the 100-year flood plain are near the toe of the southern slope of the landfill. Due to the southern slope of the landfill being near the limits of the 100-year flood plain, it is predicted that the 500-year flood would encroach on the lower portion of the side slope, therefore flood impacts are considered a causal event for this facility and mitigation measures were evaluated as part of this NWRCAP. 4.5 NON-SEISMIC LONG-TERM PERFORMANCE 4.5.1 Final Cover System The majority of the landfill final cover system for the CHSL is a soil cover, with only a small portion of the landfill (1.6 acres) covered with a LLDPE geomembrane protected by a • geocomposite and a 1-foot protective soil layer. 15 Geo-Logic ASSOCIATES