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REG 603 UPDATE-7 3/24/92 <br />• <br /> 1. 0 INTRODUCTION <br /> This update, STATUS UPDATE #7, represents data collected at the <br /> site for quarterly ground water sampling and remediation <br /> documentation during the months of February and March, 1992 . <br /> During this time a thermal oxidation unit has been operating and <br /> vapor extraction for soil and ground water remediation is taking <br /> place. Also represented in this report are quarterly ground water <br /> sampling results from samples obtained on March 10, 1992 . <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. The <br /> site lies in Section 21; T2N; R6E; MDB&M at approximately 12 feet <br /> above mean sea level (MSL) ( see Figures 1, 2, and 3 ) . The parcel <br /> is # 31 and can be located in Assessor' s Book 97 on page 41 ( 97- <br /> 041-31 ) . <br /> 1. 2 PREVIOUS REPORT (UPDATE STATUS REPORT #6, July, 1991 - <br />• January, 1992) . <br /> The following are the conclusions and recommendations of the <br /> UPDATE STATUS REPORT #6 : <br /> 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 and <br /> MW10. Ground water beneath the site contains the disolved <br /> constituents of gasoline range hydrocarbons and has spread out <br /> from beneath the site to the north MW-6, to the south M-W-7 to the <br /> west MW-9 and to the east MW-8 . <br /> Vapor extraction commenced on October 17, 1991 and up until <br /> February 3 , 1992 has operated for 1869 hours out of a possible <br /> r w ro �.� <br /> 11 ?71 nn11n Hcz of aasali-ne <br /> 2615 . 5 for a 71 . 3 run time, vA CP . WX� —j At., r--�__�� I___ <br /> range hydrocarbons. DCE, TCE and PCE screening indicates that <br /> these compounds are not present in the vapor stream at this site. <br /> Ground water sample results obtained on June 27 , 1991, prior to <br /> vapor extraction, compared to ground water sa,-aple results obtained <br /> on December 17, 1991, approximately 826 hours of operation after <br /> commencement of vapor extraction show a decline in the extent of <br /> the floating product plume as well as a decline in the dissolved <br /> constituents in monitoring wells MW4 and MW6 (the two ground water <br /> PAGE 1 <br />