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COMPLIANCE HISTORY SUMMARY Groundwater impacts were not observed at the landfill prior to first quarter 2000. Volatile organic compounds (VOCs)were first detected at well MW-3 during the first quarter 2000 monitoring event. Based on our review of the monitoring record of well MW-3 and landfilling practices conducted at FSL, the following release scenario has been developed: • Ponding occurred near MW-3 from 1995 to 1998. • In the spring of 1998, the ponding was corrected by filling the depressions and re-grading the area to drain away from refuse. • In March 2000, groundwater impact was first detected at well MW-3, approximately 4.5 years after ponding first occurred. No other wells were impacted. • In February 2002, groundwater impact was no longer detected at well MW-3, approximately four years after the ponding was corrected. • On November 6, 2002, nine months after the last detection of VOCs at MW-3, the County submitted an Evaluation Monitoring Plan(EMP) at the requirement of CVRWQCB. This EMP proposed methods to delineate the nature and extent of groundwater impact previously seen at M -3. The EMP included drilling and sampling from temporary borings, and a step-out step-down approach if groundwater contamination was detected at those borings. There were no detections. • On January 30, 2003, Waste Discharge Requirements (WDR) R5-2003-0020 was issued. The WDRs required the closure of unlined Area"I" and required the monitoring of soil gas for VOCs as corrective action measures. To comply with the soil gas monitoring requirements of the WDRs,the County commenced the analysis of VOCs from gas samples collected from the site's LFG probes that had previously been installed to comply with the LFG migration monitoring requirements set by CalRecycle. • In June 2003, an EMP was completed. The EMP consisted of the collection of groundwater samples from several temporary soil borings in the vicinity of MW-3, which resulted in no VOC detections in the water samples from the soil borings. Additionally, soil gas probe SG-1 was installed. Although, VOCs were detected at SG-1, they were not detected at MW-3 at that time. • On October 30, 2003, the County submitted an EFS presenting the results of the EMP, which indicated that corrective action was completed in 1998, and the groundwater was no longer impacted. • On May 18, 2004, subsequent to negotiations with the County, the CVRWQCB issued Cleanup and Abatement Order (CAO) R5-2004-0706, which initiated the Foothill Landfill Site Improvement Project, which included: ■ Final closure of the top deck area of Area"I" ■ Installation of an HDPE barrier (liner) between Area"I" and the future refuse placed over Area"I" in extension and completion of Area 1. Foothill Sanitary Landfill 2 Department of Public Works/Solid Waste Engineering Feasibility Study County of San Joaquin—August 2014