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R603 UPDATE-13 2/15/93 <br /> 1. 0 INTRODUCTION <br /> This update, STATUS UPDATE #13 , represents data collected at the <br /> site from December 18, 1992 through January 19, 1993 . During <br /> this time, a thermal oxidation unit was operating and vapor <br /> extraction for soil and ground water remediation was taking <br /> place . Lawrence Tank Testing (LTT) was also performing the twice <br /> a week purging of selected wells for ground water removal and <br /> 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 Once the ground water recovery - <br /> treatment system has been completed, pumping will occur from <br /> monitor wells MW1 and MW3 . <br /> 1 . 1 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; MDB&M at approximately 12 <br /> feet above mean sea level (MSL) (see Figures 1, 2 , 3 ) The <br /> parcel is # 31 and can be located in Assessor' s Book 97 on page <br /> 41 (97-041 -31) On October 2, 1992, a licensed surveyor with <br /> Nolte & Assoc surveyed all monitoring well locations and top of <br /> casing elevations to a known datum, City of Stockton Bench Mark <br /> Number 12 , elevation 11 . 74 ' above mean sea level . <br /> 1 . 2 PREVIOUS REPORT UPDATE STATUS REPORT 12 DECEMBER 1992- <br /> JANUARY, 1993 UPDATE STATUS REPORT) <br /> The following are the conclusions and recommendations of the <br /> previously submitted UPDATE STATUS REPORT #12 <br /> 4 . 0 DISCUSSION AND CONCLUSIONS <br /> As stated in earlier reports, the soil is contaminated with <br /> gasoline range hydrocarbons beneath the tank field (MW10) and <br /> along the capillary fringe of the ground water, (MW1, MW2, MW3 <br /> and MW10) , see Figure 6 Ground water beneath the site contains <br /> the dissolved constituents of gasoline range hydrocarbons and had <br /> 4.,,, "� *•, the nnrr}, IMW-91 to the eniith (KW-7) t_o the west (MW- <br /> 9)14and�to the east (MW-12) The latest ground water sampling, <br /> December 9, 1992 , shows the continual decline in the lateral <br /> extent of the plume, see Table 1 and Figures 5A and 5B <br /> Vapor extraction started October 17, 1991 and has operated for <br /> 5388 hours (December 18 , 1992) out of a possible 8821 . 5 hours, <br /> 611r run time, destroying 48310 pounds of gasoline range <br /> hydrocarbons . Since the last status report, November 17, 1992, <br /> 8768 pounds of gasoline range hydrocarbons have been <br /> PAGE 1 <br />