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INTRODUCTION This update, STATUS UPDATE 47, presents data from January 15, through March 18, 1997 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, RGE, 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 feet above mean sea level GROUNDWATER MONITORING Depth to groundwater measurements and vacuum readings were obtained from all monitor wells on March 18, 1997 . Water samples were obtained from all wells associated with this site MW1 through MW12 at that time The vapor extraction system (VES) is monitored weekly and was operating at the time of the quarterly sampling/monitoring 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 March 18, 1997 Groundwater gradient shows a recharge cycle The overall flow direction is predominately to the east with localized drainage at MW1 from MW10 or westardly GROUNDWATER SAMPLING On March 18 , 1997, quarterly groundwater samples were obtained from all 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 642 respectively Confirmation of MTBE using EPA method 8060 was made on samples obtained fro monitor wells MW4 , MW11 and MW12 only MW11 confirmed MTBE, see Appendix A, Table 1 and Figure 5 The next 40 quarterly sampling will occur in June, 1997 . PAGE 1 R603 UPDATE-47 04/03/97