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Californi gional Water Quality Co l Board <br /> Central Valley Region <br /> Karl E.Longley,ScD,P.E.,Chair <br /> Linda S.Adams Sacramento Main Office Arnold <br /> Secretary for 11020 Sun Center Drive 4200,Rancho Cordova,California 95670-6114 Schwarzenegger: <br /> Environmental [) Governor <br /> Protection Phone(916)464-3291•FAX(916)464 4645 �� <br /> http://www.waterboards.ca.gov/centralvalley <br /> 22 August 2007 q�q IR 0G 2 7 2001 <br /> PN V IVIS J d HEALTH <br /> Mr. Kevin Basso, General Manager IOERMIT/SERVICES <br /> Forward Inc. <br /> 1145 West Charger Way <br /> Stockton, CA 95206 <br /> REVIEW OF 2007 ANNUAL CORRECTIVE ACTION EVALUATION REPORT, AUSTIN <br /> ROA® LANDFILL, SAN JOAQUIN COUNTY <br /> Regional Water Quality Control Board staff has reviewed the 2007 Annual Corrective Action <br /> Evaluation Report, Austin Road Landfill(report) and has the following comments: <br /> 1. The isoconcentration maps in Appendix E compare current VOC concentrations with <br /> concentrations predicted by pre-construction computer simulations from the 2001 <br /> Revised Engineering Feasibility Study. The actual results are generally better than the <br /> concentrations predicted by the simulations. However, maps included in Appendix E <br /> are somewhat misleading because they do not incorporate data from wells 8106A and <br /> 7898. Figures E-1, -2, and -3 should be revised to include data from 8106A and 7898A <br /> and submitted to the Water Board by 28 September 2007. <br /> 2. The report demonstrates that the three corrective action evaluation criteria were not <br /> exceeded. The three criteria are: 1) site wide total VOC mass Threshold Limit, 2) site <br /> wide total VOC mass increase for four consecutive monitoring events or 3) an individual <br /> well Threshold Limits. Threshold Limits were established for new well AMW-18. <br /> 3. The report proposes four supplemental groundwater monitor wells to investigate the <br /> source, the horizontal extent and vertical extent of VOCs in Northern California Youth <br /> Center (NCYC) water supply wells. Staff understands that the actual location of the <br /> wells may change depending on access, utilities and NCYC approval. Staff concurs <br /> with the four proposed wells and recommends that Forward install a fifth well near the <br /> AMW-17 location. This will fill in a gap in the groundwater monitoring system. Perhaps <br /> a below grade wells can be installed at the ARL-1 B and AMW-17 locations with a traffic <br /> rated vaults in the NCYC perimeter road? <br /> 4. The tops of well screens for the NCYC wells range from 124 to 142 feet below ground <br /> surface and the bottoms range from 318 to 505 feet below ground surface. <br /> Groundwater levels are approximately 60 feet below ground surface and the existing <br /> monitor well system is designed to monitor the upper part of the groundwater column. <br /> If Austin Road is the source of VOCs in the NCYC wells, the VOCs are migrating in <br /> aquifer horizons below 125 feet. The report proposes to screen the supplemental wells <br /> between 155 and 175 feet. Staff recommends that you attempt to identify the aquifer <br /> zones transmitting VOCs by collecting discrete depth water samples at least at the first <br /> California Environmental Protection Agency <br /> Qa Recycled Paper <br />