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1 <br /> r � <br /> 100 Pringle Avenue. Suit, D <br /> Walnut Creek,CA 94596 4 <br /> 415-945-3000 Woodwew d■Clyde Consultants <br /> September 30, 1986 <br /> Mr. Ron Valinoti <br /> Assistant Director <br /> San Joaquin Local Health District <br /> 1601 East Hazelton Avenue <br /> Stockton, CA 95201 <br /> Dear Mr. Valinoti: <br /> This letter has been prepared on behalf of LOF Glass Company and is in <br /> response to your request for a Site Cleanup Assessment Plan for subsurface <br /> hydrocarbon contamination discovered recently at the LOF Lathrop, <br /> California facility. The soil contamination was discovered during the <br /> removal of the smaller (550 gal .) of two underground gasoline storage <br /> tanks. The adjacent 5,000 gal , tank is being left in service although it <br /> has been partially uncovered to permit the installation of an inventory <br /> reconciliation monitoring system. The tank locations and general <br /> groundwater gradient are shown in Figure 1. In conjunction with the <br /> removal of the smaller tank, a soil sample was taken from beneath the fill <br /> pipe end of the tank. The sample was found to contain only 49 mg/kg total <br /> hydrocarbons although BTX levels were relatively high. The tank pit was <br /> backfilled with clean materials to avoid a safety hazard. The following <br /> discussion outlines our recommendations for the investigation and <br /> remediation of the subsurface contamination. <br /> The available information has been reviewed and suggests that the <br /> contamination may be limited and is probably confined to the immediate <br /> vicinity of the tank. This is based on the fact that the tank has not <br /> experienced any known spills or inventory losses during its time in service <br /> and that following removal , the tank was inspected and appeared to be in <br /> sound condition. Observations made during removal did not note any <br /> significant evidence of contamination other than a strop odor. In <br /> addition, the excavation around the adjacent tank extends below the water <br /> table and no evidence of hydrocarbons were apparent on the groundwater <br /> surface during our inspection. The existing contamination is most likely a <br /> result of a single or occasional overfilling of the tank. <br /> The recommended investigation and mitigative measures included obtaining a <br /> groundwater sample from the adjacent tank excavation and removing the <br /> contaminated soil surrounding the former location of the removed tank. The <br /> water sample wil be taken by first pumping three to four volumes of water <br /> from the excavation and then taking a sample from just below the surface. <br /> The sample will be analyzed for total petroleum hydrocarbons and BTX using <br /> EPA method 5020 or 5030. The contaminated soil will be removed from the <br /> Consulting Engineers,Geologists <br /> and Environmental Scientists <br /> Ni V; <br /> Offices in Other Principal Cities - — '•• _=.-.L?;� - <br /> r- <br />