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n <br />LJ <br />5.4.3.2. Site Groundwater Quality <br />Groundwater quality is monitored with one up -gradient and two down -gradient wells. The Site <br />Improvement Project of 2006 is intended to include one additional up -gradient well and one <br />additional down -gradient well, the location to be determined by the Regional Water Quality <br />Control Board. <br />The groundwater at the Foothill Landfill does not appear to be impacted by the landfill at this <br />time (First Semester 2005 Groundwater and Surface Monitoring Report, San Joaquin County, <br />June 2005). Groundwater is monitored in accordance with the waste discharge permit <br />requirements. The groundwater is sampled semi-annually. <br />Prior to March 2000, impacts to groundwater were not indicated. From March 2000 to October <br />2001, volatile organic compounds (VOCs) were detected at groundwater monitoring well MW -3. <br />These detections have been ascribed to impact by LFG due to ponding along a road on refuse <br />immediately adjacent to well MW -3 during the winters of 1995/1996, 1996/1997, and <br />1997/1998. Impact to groundwater was not indicated at other wells. <br />As a result of the groundwater impact at MW -3, the WDRs required an Evaluation Monitoring <br />Program, which was completed June 2003. Groundwater samples from temporary borings were <br />found free of contaminants. A soil gas well, SG -1, was bored to sample soil gas above the water <br />table near groundwater monitoring well MW -3. Four VOCs were detected in gas samples taken <br />from SG -1; however, these compounds were not detected in the water samples taken at MW -3. <br />Monitoring data from MW -3 continues to show no impact by VOCs. <br />Corrective action taken to prevent ponding has apparently resulted in the elimination of impact <br />by landfill gas, as indicated by lack of confirmed VOC detections in groundwater since October <br />2002. <br />Sulfate exceeded the concentration limit in the background (up -gradient) well, MW -1 during that <br />sampling event. Because this data was found in the up -gradient well, the County concludes that <br />this is not due to impact by the landfill, but rather the result of other effects off site, and not <br />involving the landfill. <br />Foothill Sanitary Landfill Page 28 of 62 Public Works/Solid Waste <br />JTD County of San Joaquin — Revised 10/6/05 <br />