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Emeon Associates <br /> 1433 North Market Boulevard.Sacramento,California 95834-1943. (916)928-3300. Fax(916)928-3341 <br /> October 3, 1994 <br /> Project 0805-109.01 <br /> Mr. Michael Infurna OCT l 0 10,% <br /> San Joaquin Public Health Services IENVIR( ,,,icit;i . ,AFH <br /> P.O. Box 2009 PERMIT/SERVICES <br /> Stockton, California 95201 <br /> Re: Addendum to Problem Assessment Report ARCO Service Station No. 2168 <br /> at 441 Charter Way, Stockton, California <br /> Dear Mr. Infuma: <br /> At the request of ARCO Products Company (ARCO), EMCON Associates (EMCON) has <br /> prepared this addendum to the Problem Assessment Report (PAR), prepared by RESNA <br /> Industries (RESNA, June 10, 1994) for the subject site. <br /> The PAR was prepared and submitted following an off-site investigation upgradient from <br /> the ARCO site. High concentrations of gasoline hydrocarbons were detected in soil and <br /> groundwater during the off-site investigation. Based on data collected to date, EMCON <br /> believes that hydrocarbons detected near capillary fringe soil and in groundwater emanate <br /> from an off-site source. This addendum outlines remedial alternatives which were not <br /> presented in the PAR. <br /> REMEDIAL ALTERNATIVES <br /> Based on the size of the site, the extent and concentrations of the hydrocarbons in soil <br /> and groundwater, and the type of soil present at the site, in-situ bioremediation, chemical <br /> neutralization, and slurry wall containment are not technically or economically feasible <br /> remedial options. The following options are presented. <br /> Soil Remediation <br /> Excavation. Due to a release of approximately 2 to 5 gallons of gasoline during drilling <br /> operations, residual hydrocarbons have been detected in soil and are present near the <br /> product line located at the eastern portion of the northern dispenser island at relatively <br /> shallow depths. The removal of this hydrocarbon bearing soil is feasible by excavation <br /> in conjunction with future removal of the underground storage tanks. Residual <br /> hydrocarbons were also detected in the capillary fringe zone (approximately 40 feet below <br /> surface grade [bsg]). Excavation as a remedial alternative will require removal of all site <br /> SAC/pift805 08051090.1cs-94 puA <br />