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Draft Cleanup and Abateme rder No. R5-2008- - 3 - Forward 3 - Forward Landfill San Joaquin County GROUNDWATER IMPACTS FROM THE AUSTIN ROAD LANDFILL 11.Significant volatile organic compound (VOC) groundwater impacts including, but not limited to, 1,1-dichloroethane, cis-1,2-d ichloroethylene, tetrachloroethylene, and trichloroethylene are associated with waste discharged to the Austin Road Landfill. Impacts were initially detected in 1989. By 1991, evaluation monitoring determined that chlorinated hydrocarbon impacts extended as far as 1,000 feet down-gradient from the Austin Road Landfill. A corrective action plan, consisting of a phased approach to remediate the plume, was approved in 1991, but by 1998 it was apparent that the initial corrective actions had failed to remediate the groundwater impacts because detections of 1,1-dichloroethane, cis-1,2-dichloroethylene, tetrachloroethylene, and trichloroethylene were still detected in downgradient monitoring wells. 12.The Discharger stated in its 2002 Joint Technical Document that "the VOC polluted groundwater extends approximately 4,000 feet northeast from the northern border of the existing Austin Road Landfill. The plume appears to have migrated to a lower depth at the leading edge of the plume. The primary contaminants of concern are Tetrachloroethylene and Trichloroethene, with concentrations levels up to 59 and 48 micrograms per liter, respectively. The highest VOC concentrations are present within a sand layer that extends beneath the site between approximately 80 to 104 feet below ground surface." 13.There are no monitoring wells installed at the downgradient edge (vertically or laterally) of the plume. 14.In 2003, the Central Valley Water Board adopted WDRs Orders R5-2003-0049 and R5-2003-0080 to implement revised corrective actions to remediate groundwater impacts. The Discharger extracts groundwater from two wells adjacent to the northern boundary of the Austin Road Landfill, and then runs it through an air sparger prior to discharging the effluent to an infiltration area. From 1 October through 31 December 2007, the two wells extracted at an average rate of 209 gallons per minute or 301,000 gallons per day. Based on the continuing detections in the downgradient wells, the current extraction rate is insufficient to control the plume and remediate the release of waste from the landfill. 15.The Austin Road Landfill corrective action monitoring system includes monitoring wells AMW 13 and AMW 14. These wells are approximately 1,600 feet directly downgradient of the two extraction wells EW-1 and EW-2. During the first Quarter 2008 sampling event the following VOCs concentrations were detected in these wells: