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'• INTRODUCTION This update, STATUS UPDATE 45, presents data from June 27, through October 17, 1996 and includes the Quarterly Groundwater Sampling, Vapor Extraction System Monitoring and Venting of MWS . The permit to dump treated groundwater to the sewer has been renewed Presently we are batch dumping the treated water from the "ConVault" whenever it is full . The water for treatment is collected from the vapor recovery condensate dropouts and produced from the sampling and monitoring of the monitor wells by Lawrence Tank Testing (LTT) pumping service LOCATION The station is located at 6425 Pacific Avenue at the intersection of Douglas Road, Stockton, in San Joaquin County, California . The site lies in Section 21, T2N, R6E; MDB&M at approximately 12 feet above mean sea level (MSL) (see Figures 1, 2 , 3) . The parcel is # 31 and can be located in Assessor' s Book 97 on page 41 (97-041-31) On October 2, 1992, a licensed surveyor with Nolte & Assoc surveyed all monitoring well locations and top of casing elevations to a known datum, ie City of Stockton Bench Mark Number 12, elevation 11 74 ' above mean sea level GROUNDWATER MONITORING Depth to groundwater measurements and water samples were obtained from all monitor wells on June 20, July 30, and September 19, 1996 The vapor extraction system (VES) was operating at those times Corrections for vacuum were necessary for the depth to water measurements, see Appendix D - Field Notes and Methods and Proceedures Figure 4, represents the measurements obtained on September 19, 1996 Groundwater gradient shows a discharge cycle, with the exception of MW2, groundwater has dropped from 0 35 feet at MW8 to 2 69 feet at MW1, averaging a little over 1 foot across the site A low pressure basin has formed at the wells being used for vapor recovery (MW1, MW3 and MW10) The overall flow direction is predominately to the east GROUNDWATER SAMPLING On September 1.9, 1996 , quarterly groundwater samples were oiDcained from all of the wells, see Table 1 and Appendix A. These samples were collected by a WEGE Geotechnician and "Chain of Custody" delivered on ice to a State certified testing laboratory, AMERICAN ENVIRONMENTAL NETWORK, INC. DHS #1172, for chemical analyses. These samples were analyzed for TPH, BTEX and MTBE concentrations using EPA Methods 8015/5030 and 602 respectively, see Appendix A, Table 1 and Figure 5 The next quarterly sampling will occur in December, 1996 PAGE 1 R603 UPDATE-45 11/07/96