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• The County has already committed to expanding the final cover system to extend over the 1.3-acre segment of waste that lies outside of the current closure area and to installing additional landfill gas extraction wells in that area. Monitoring of groundwater quality at the point of compliance wells (MW-5, MW-8, and SB-1) would continue as a means to evaluate the effectiveness of closure cover and gas extraction efforts. Monitoring of the three EMP wells (MW-9A, MW-10A, and MW-11A) would be continue to evaluate intrinsic remediation of VOC impacted groundwater passing the point of compliance. By preventing natural intrusion of air into the refuse and the venting of landfill gas generated in this area of the site, construction of the final cover system extension may result in temporary increases in VOC concentrations at point-of-compliance groundwater monitoring wells. Once the landfill gas extraction system enhancements are operational and adjusted to optimize collection, VOC impacts to groundwater should begin to diminish, assuming that there are no sources of VOCs other than the landfill that contribute to VOCs impacts to the shallow aquifer. Monitoring of landfill gas and groundwater chemistry will be conducted to evaluate the effectiveness of the corrective actions. • The County will document construction of the new landfill gas extraction wells and final cover system extension, and will report to the Central Valley RWQCB upon completion of the construction project. Construction of the EMP wells has been documented and submitted to the Central Valley RWQCB in the CHSL EMP Report (GLA, 2012). Operations, monitoring, and maintenance of the final cover, landfill gas extraction, and groundwater monitoring systems will be reported annually as part of the annual groundwater monitoring report. The annual monitoring will continue to include collection and analysis of groundwater chemistry data, landfill gas chemistry data, and erosion control and settlement observations for the final cover system. 6.2 CORRECTIVE ACTION IMPLEMENTATION PLAN With the submittal of this EFS, the County reaffirms its commitment to proceed with corrective actions to mitigate VOC impacts associated with the CHSL. The corrective action approach outlined in Section 6.1 represents an appropriate course of action based on site- specific data; however, in concert with these corrective actions the County will implement a corrective action plan to monitor, maintain, and improve corrective actions at the site until • compliance with federal and State of California regulations is achieved (Figure 12). Engineering Feasibility Study Geo-L.og0c Page ■ 33 Corral Hollow Sanitary Landfill ASSOCIATES January 25,2013