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5 <br /> Mr Paul Supple Project 20805-140 006 <br /> . January 28, 1998 <br /> Page 2 <br /> RESNA began monitoring the groundwater in wells MW-1 through MW-4 on <br /> October 30, 1991 (RESNA, June 26, 1991, Report No 30004-4) Wells MW-5 and <br /> MW-6 were added to the monitoring program in March 1993 and December 1993, <br /> respectively Dissolved hydrocarbons have been detected in wells MW-1 and MW-5 since <br /> monitoring began <br /> In March 1992, EA Engineering, Science and Technology (EA) observed removal of the <br /> oil-water separator/clarifier (EA, August 1992, Report No 80633 01) EA collected one <br /> soil sample from beneath the former oil-water separator and one sample from the <br /> concrete Analytical results from the soil samples indicated that oil and grease (quantified <br /> as total oil and grease) were present Concentrations of volatile organic compounds, <br /> semivolatile organic compounds, and polychlorinated biphenyls were below detection <br /> turuts Total metals were also below detection limits, with the exception of arsenic and <br /> barium, which were detected at concentrations of 0 0051 and 0 12 parts per million, <br /> respectively <br /> On March 2, 1992, RESNA conducted a vapor extraction test at the site (RESNA, <br /> June 15, 1992, Report No 30004-5) Results of the test indicated that soil beneath the site <br /> • can be remediated by vapor extraction, and the evaluated radius of influence was 30 feet <br /> In May 1994, RESNA submitted a problem assessment report (RESNA, May 11, 1994, <br /> Report No 30004-8) to the San Joaquin County Public Health Services (SJCPHS) and the <br /> California Regional Water Quality Control Board. A final remediation plan will be <br /> prepared by EMCON, and subsequent remediation will be implemented in the future <br /> EMCON subrrutted a workplan dated July 23, 1996, for activities associated with removal <br /> of the USTs The scope of work includes tank and piping removal oversight, collection of <br /> soil samples, abandonment of well MW-3, and installation of a new vapor extraction well <br /> The scope of work will be implemented concurrent with the UST removal The <br /> July 23, 1996, workplan also supersedes an October 5, 1995, workplan and a <br /> November 14, 1995, addendum to the October 5 workplan. <br /> The UST removal permit applications are currently being reviewed by the SJCPHS UST <br /> removal will occur after the permits are issued <br /> PROPOSED SCOPE OF WORK <br /> The purpose of this investigation is to further delineate dissolved hydrocarbons <br /> downgradient of the USTs Field work will be conducted following Th-Regional Water <br /> Quality Control Board Guidelines EMCON field procedures are presented in the j <br /> • appendix EMCON proposes to conduct the following scope of work <br /> SAC,N\PJfA080%8051400 6AS-99cbeli 2 <br />