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On November 6, 2002, nine months after the last detection of VOCs at MW-3,the County submitted an Evaluation Monitoring Plan at the requirement of RWQCB staff. This Plan proposed methods to delineate the nature and extent of groundwater impact previously seen at MW-3, as required. The Plan included drilling and sampling from temporary borings, and a step-out step- down approach if groundwater contamination was detected at those borings. On January 30, 2003, eleven months after the last detection of VOCs at MW-3, the California Regional Water Quality Control Board, Central Valley Region(CVRWQCB), issued WDRs. These WDRs required the closure of Module"I" as corrective action because Module"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. Monitoring data from MW-3 continues to show no impact by VOCs. Based on this data,the County concluded that the groundwater impact had ceased since February 2002, and that the corrective action of removing the ponding had prevented further groundwater impact. 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 Module `I'. This Order did not require the submittal of a Closure Plan(the Preliminary Closure Plan was on file with RWQCB 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 Module"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 since . On December 16, 2003, an Administrative Civil Liability Complaint was issued by the CVRWQCB for"not submitting a Closure Plan for Module `I"'. At this time, groundwater contamination had not been detected at MW-3 for nearly two years. 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 includes: • Final closure of the crest of Module "I" Installation of a barrier between Module "I" and the future refuse placed over Module ® "I"in extension and completion of Module 1 Foothill Sanitary Landfill 3 Department of Public Works/Solid Waste 1"Semester 2010 Groundwater Monitoring County of San Joaquin—July 21,2010