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• Global Presence Personal Attention HERST &ASSOCIATES, INC. Mr. Howard Hold California Regional Water Quality Control Board Central Valley Region 11020 Sun Center Drive, Suite 200 Rancho Cordova, California 95670-6114 July 30, 2014 Dear Mr. Hold: 2014 Annual Corrective Action Evaluation Report, Austin Road Landfill, San Joaquin County, California In February 2002, the Austin Road Landfill submitted a report titled Evaluation Procedures for Proposed Corrective Action at Austin Road Landfill, Addendum to May 2001 EFS (Revised August 2001) (Evaluation Procedures Report). The February 2002 report described procedures that would be followed to verify the continued effectiveness of previous and future corrective action measures at the site using groundwater quality results. Corrective actions implemented to date at the Austin Road Landfill includes landfill gas management, groundwater pumping, and an artificial groundwater • recharge area. Landfill gas collection began in 1985. Groundwater pumping at extraction wells EW -1 and EW -2 has reportedly been underway since 1994. Groundwater pumping at extraction well EW -4 has reportedly been underway since May 2009. Groundwater pumping at extraction well EW -3R has reportedly been underway since October 2009. The artificial recharge area was constructed in October 2002 and has reportedly been in use since May 2003. The February 2002 report described three criteria that would be used to determine if a groundwater exceedance has occurred: ➢ A total VOC mass Threshold Limit exceedance, ➢ A total VOC mass increase for four consecutive events, or ➢ An individual well total VOC concentration Threshold Limit exceedance. Using available groundwater volatile organic compound (VOC) data, a threshold limit was calculated for total VOC mass in the impacted groundwater. The threshold VOC mass limit represents the upper bound of typical VOC mass in the impacted groundwater. A value above the threshold VOC mass limit would be suggestive of potential increasing VOC concentrations on a plume -wide basis. An increase in total VOC mass over four consecutive quarters would also suggest possible increasing VOC concentrations on a plume -wide basis, and was therefore included as a second evaluation criteria. Finally, historic individual well total VOC concentrations were used to develop well -specific threshold limits. A value above an individual well's threshold VOC limit would be suggestive of potential increasing VOC concentrations in that particular well. is 4631 North St. Peters Parkway Telephone (636) 939-9111 St. Charles, Missouri 63304 Fax (636) 939-9757