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On January 30, 2003, eleven months after the last detection of VOCs at MW-3, the CVRWQCB issued WDRs. These WDRs required the closure of Area"I" as corrective action because Area"I" is unlined and "assumed to be the source of contamination". These WDRs also required the monitoring of soil gas for VOCs. Groundwater contamination was not indicated at that time. In June 2003, one and one-half years after the last detection of VOCs at MW-3,the Evaluation Monitoring Program was completed. Groundwater samples from temporary borings were found free of contaminants, consistent with data from the permanent monitoring wells since February 2002. A soil gas well, SG-1, was bored to sample soil gas above the water table near groundwater monitoring well MW-3. Four VOCs were detected at SG-1; however,these compounds were not detected in the water samples taken at MW-3 at that time. Monitoring data from MW-3 until most recently did not show an impact by VOCs. Based on that data,the County concluded that the corrective action of removing the ponding had prevented further groundwater impact at that time. On September 16, 2003, due to delay in submitting the results of the Evaluation Monitoring Plan,the CVRWQCB issued a Water Code Section 13267 Order. This Order required that the County submit the results of the Evaluation Monitoring Program and an Engineering Feasibility Report that includes closure of Area `I'. That Order did not require the submittal of a Closure Plan(the Preliminary Closure Plan was on file with CVRWQCB at that time). On October 30, 2003,the County submitted a final Engineering Feasibility report to the CVRWQCB presenting the results of the Evaluation Monitoring Program which indicated that the groundwater was no longer impacted. Corrective action was identified as completed in 1998 -preventing further ponding on the landfill surface near MW-3. Closure of Area"I" was discussed,but was not proposed as further corrective action due to the apparent success of previous corrective action indicated by the of lack of groundwater contamination. On December 16, 2003, an Administrative Civil Liability Complaint was issued by the CVRWQCB for"not submitting a Closure Plan for Area `I"'. At that time, groundwater contamination had not been detected at MW-3 for nearly two years and no other groundwater monitoring well indicated contamination: groundwater was not impacted. Negotiations in January 2004 resulted in a Clean Up and Abatement Order which requires the County to initiate the Foothill Landfill Site Improvement Project, which included: • Final closure of the top deck area of Area"I" • Installation of a barrier between Area"I"and the future refuse placed over Area"I" in extension and completion of Area 1 • Landfill gas collection • Placing Partial Cover of those surfaces of Area"I"that are not covered by the inter-Area barrier or final closure ® Installation of two groundwater monitoring wells This project was to be pursued in lieu of complete closure of Area"I". On July 20, 2004,the San Joaquin County Board of Supervisors approved a contract with Kleinfelder to design the Site Improvement Project. In mid-2006,the gas-impermeable HDPE liner material was placed over Area"I"refuse. Foothill Sanitary Landfill 3 Department of Public Works/Solid Waste 15`Semester 2014 Groundwater Monitoring County of San Joaquin—July 31,2014