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ArKDAMES & MOORE APROFESSIONAL I IMITED PARTNERSHIP <br /> The site-specific soil cleanup level was devel ped following the <br /> performance of a baseline risk assessment and feasibility study <br /> conducted in general accordance with the State of California Site <br /> Mitigation Decision Tree Manual. The purpose cf the risk <br /> assessment was to identify and conservatively estimate risks posed <br /> by existing site conditions and develop remedial action goals which <br /> if meet, would be protective of the public health and environment. <br /> Based on the identified risks, Dames & Moor developed several <br /> remedial action alternatives. These alternate es were then <br /> screened based on technical feasibility, public health and <br /> environmental protectiveness, institutional recuirments, and cost <br /> effectiveness. It is our judgement that the p oposed remediation <br /> plan, which includes excavation of approximately 1200 cubic yards <br /> of contaminated soil to a depth of approximately 30 feet below <br /> ground surface in the vicinity of the former and rground tanks will <br /> effectively remove the most highly contaminate soils and further <br /> reduce potential impact to the underlying grou dwater. <br /> It is our understanding that the San Joaquin Local Health <br /> District has the authority under the California Underground Storage <br /> Act to act as the lead agency for overseeing the underground <br /> storage tank cleanup at this site. In an April 7 , 1988 letter to <br /> Mr. Mary Palmer of AM&M from the Department of Health Services <br /> (DHS) , the DHS stated that the San Joaquin Local Health District <br /> and the Central Valley Regional Water Quality ontrol Board have <br /> authority and expertise to establish cleanup 1 eels for soil and <br /> groundwater, respectively. Given that groundwater has not <br /> apparently been impacted by the presence of diesel fuel in the <br /> soils, the establishment of groundwater cleanup levels is not <br /> applicable to this site. The 50 ppm cleanup level for soils <br /> referenced in a September 26, 1986 letter from DHS specifically <br /> refers to EPA 8240 compounds, not total petro eum hydrocarbons. <br /> Dames & Moore, has been and is currently coopera ing with Ms. Diane <br /> Hensen of your agency to resolve this issue. In addition, we have <br /> provided copies of the FS/RAP report and the results of additional <br /> groundwater monitoring to the DHS. <br /> AM&M has raised concerns that site investigations to date <br /> have not adequetly evaluated the potential for groundwater impact, <br /> and that the existing groundwater monitoring wall network is not <br /> adequete to detect the migration of diesel fuel or its components <br /> from the soil to the underlying groundwater due to the distance of <br /> the wells from the source. The existing network consists of three <br /> wells, two of which are located hydraulically do ngradient from the <br /> contaminant source area, and one upgradient of the source area. <br /> The two downgradient wells (MW-2 and MW-3) are located <br /> approximately 75 feet and 190 feet from the former tank locations. <br /> Dames & Moore has concluded that the likelihood that groundwater <br />