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R603 UPDATE-17 5/24/93 <br /> 1 .0 INTRODUCTION <br /> This update, STATUS UPDATE #17, represents data collected at the <br /> Bite from April 23 , through May 18, 1993 . During this time, a <br /> thermal oxidation unit was operating and vapor extraction for <br /> soil and ground water remediation was taking place . Lawrence <br /> Tank Testing (LTT) was also performing twice a week purging of <br /> selected wells for ground water removal and treatment . <br /> The permit to dump treated ground water to the sewer was received <br /> and presently we are batch dumping the treated water from the <br /> "ConVault" monthly. This water is collected from the vapor <br /> recovery condensate dropouts and the twice weekly purging of <br /> monitor wells MW1, MW2, MW3, MW8 and MW10 by Lawrence Tank <br /> Testing (LTT) pumping service There was no water dumped to the <br /> sanitary sewer during the month of May, 1993 . <br /> LOCATION <br /> The station is located at 6425 Pacific Avenue at the intersection <br /> of Douglas Road, in San Joaquin County, Stockton, California <br /> The site lies in Section 21; T2N, R6E, MDS&M at an elevation that <br /> ranges between 11 . 5 to 13 feet above mean sea level (MSL) (see <br /> Figures 1, 2, 3) The parcel is # 31 and can be located in <br /> Assessor' s Book 97 on page 41 (97-041-31) . <br /> 2 . 0 GROUND WATER <br /> LOCAL GROUND WATER FLOW <br /> Ground water flow direction in this region is to the west and <br /> towards south Stockton from the foothills of the Sierra Nevada <br /> Mountain Ranges, and towards the east from the Sacramento-San <br /> Joaquin Delta . At present, encroachment of saline waters from <br /> the Delta is impairing the quality of the ground water in the <br /> Stockton area Starting on December 1, 1992 , LTT has been <br /> performing twice a week purging of monitor wells MW1, MW2, MW3 , <br /> MW8 and MW10 . The twice a week well purging was reduced to once <br /> a week in May, 1993 . This purging is creating a ground water low <br /> (cone of depression) beneath the site near MW1 and MW2 , see <br /> Figures 4A - April, 1993 and 4B - May, 1993 . <br /> GROUNDWATER CUARTERLY_SAMPLING <br /> Ground water samples were collected on March 11, 1993 , see Table <br /> 1 . These samples were collected by a WEGE geologist and "Chain <br /> of Custody" delivered on ice to a state certified testing <br /> laboratory (SUPERIOR PRECISION ANALYTICAL, INC. DHS##1332) for <br /> chemical analyses These samples were analyzed for TPH and BTEX <br /> concentrations using EPA Methods 8015 and 602 respectively. <br /> The next quarterly sampling will occur in June, 1993 . <br /> PAGE 1 <br />