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VOCs above the trace level have not been detected at G-4 since January 2003. All other groundwater wells continued to be free of VOCs. Note that VOCs are found at many of the soil gas wells, but not in the groundwater, indicating that the presence of VOCs in the soil does not necessarily indicate the potential for impact to groundwater. Although groundwater impact has not been seen since January 2003,the results of the first phase of evaluation monitoring allowed the County to delineate the problem sufficiently to proceed with engineering feasibility of corrective action options. It was apparent that the cause of the impact at G-4 was landfill gas (LFG), and that sporadic detections at G-4 could occur in the future unless corrective action was taken. After evaluating soil gas extraction as a possible method to prevent further impacts to G-4,the County submitted an addendum to the Engineering Feasibility Study with associated Amended Report of Waste Discharge(December 21, 2004). This addendum proposed active LFG collection. In accordance with the Report of Waste Discharge (January 29, 2010), all groundwater monitoring wells will continue to be sampled semi-annually for field and monitoring parameters per the WDRs. Soil gas continues to be sampled semi-annually per the WDRs. This data is included in semi-annual reports for this site. The LFG system was installed in the autumn of 2006, and has been in full operation since May 2007. Groundwater continues to be un-impacted by the landfill. Due to falling groundwater elevations, reliable samples could no longer be collected from wells G-2 and G-5. These wells were replaced with wells G-2A and -5A this semester, each installed nearby the well they replaced. Analyses of samples taken from the replacement wells are consistent with the most recent analyses from the wells they replaced. r MONITORING PROGRAM Water quality is monitored consistent with WDR Order No. R5-2010-0016. Groundwater The groundwater well network consists of up-gradient well G-1 and down-gradient wells G2-A G-3 D, G-4, G5A and G-6 (Figure 3). Replacement down-gradient wells G-2A and G-5A were installed during the 2°a Semester 2013. Groundwater samples are analyzed semiannually for the following field and monitoring parameters as specified in WDR Order No. R5-2010-0016. Temperature Total Alkalinity Electrical Conductivity (EC) Total Hardness pH Chemical Oxygen Demand (COD) North County RC&SL Public Works/Solid Waste 2otl Semester and Annual 2013 Groundwater Monitoring 3 County of San Joaquin—January 25,2014