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3-15 treatment facility consisted of two extraction wells, EW -1 and EW -2. These wells and the groundwater treatment facility are still functional and operating and groundwater is extracted at a rate of approximately 50 to 85 gpm for E-1 and 85 to 120 gpm for EW -2. In order to better understand the dimensions and impacts of the plume, the RWQCB ordered further investigations to be conducted. In January 1999, Camp Dresser & McKee (CDM) prepared the "Austin Road Landfill Contaminant Plume Report" and the "Groundwater Corrective Action Feasibility Study Report". In addition, bottled water is supplied to all downgradient well owners where there has been a detection of any VOCs above drinking water standards. This has been performed since 1997 when downgradient wells first detected PCE above 5 pg/L. Based on these reports, the VOC contaminant plume was estimated to extend approximately 4,000 feet northeast (downgradient) from the northern border of the Austin Road Unit. The plume appears to have migrated to a lower depth at the leading edge of the plume. The primary contaminants of concern are perch loroethylene (PCE) and trichloroethylene (TCE), with concentration levels up to 69 and 48 micrograms per liter (pg/L), respectively. The highest VOC concentrations are present within a sand layer that extends over an interval of approximately 80 to 104 feet below ground surface (bgs). The investigation results indicate that contaminant concentrations decrease at distances from the source, with the plume migrating in deeper lithologic units at a distance from the site. The plume shape reflects the north to northeast groundwater flow direction, with the leading edge of the plume extending east of Austin Road. The contaminant plume is moving at a similar rate, approximately 4 feet per day, as the general groundwater flow rate. This suggests that VOC migration rates are not affected significantly by sorption of contaminants to aquifer materials. The trend of reduced contaminant concentrations away from the landfill is attributed primarily to dilution occurring through mixing with unimpacted groundwater and with surface water recharge. Forward Landfill has been addressing groundwater quality impacts associated with the City of Stockton's unlined landfill since Forward purchased the former Austin Road Landfill from the City in 2000. It is possible that the VOC impacts in groundwater at the Austin Road Unit are attributable to landfill gas. VOC concentrations have been trending downward, and leachate analyses from the Austin Road Unit indicate no significant VOCs. VOCs are detected, however, in landfill gas samples. Forward Inc. has assessed landfill gas and groundwater issues at the Austin Road Unit and, as required by the RWQCB, a revised Engineering Feasibility Study (EFS) was prepared for the Corrective Action Program (HA/AEE, 2001). The revised EFS that was completed by HA/AEE involved review of available data and preparation of a detailed groundwater flow and transport model to assess the most efficient means of controlling groundwater impacts at the Austin Road Unit. The model incorporated hydrogeologic and hydrochemical information that were collected in previous investigations of the landfill, and included data collected in aquifer pumping tests that were completed at the site. Forward Landfill SWT Engineering Joint Technical Document - April 2014 z:\projects\allied waste\forward\five year permit rvw 2013\jtd-5 yr pr 2013\text\sec 3_final.doc