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1 <br /> Feasibility Study/Corrective Action Plan November 26 1996 <br /> The Drake Property,26485 Thornton Road Thornton California <br /> 1 4 INTRODUCTION <br /> This Feasibility Study/Corrective Action Plan for the Drake Property, located at 26485 Thornton Road, <br /> Thornton, California (Figures 1 and 2), presents an analysis of three alternate approaches to obtaining site <br /> closure This study Is presented in response to the March 29, 1996 written request from the San Joaquin <br /> County Public Health Services, Environmental Health Division (SJCPHS-EHD) In keeping within recent <br /> guidelines issued by the California State Water Resources Control Board (CSWRCB, 1995), and the <br /> California Regional Water Quality Control Board, Central Valley Region (CWQCB-CVR, 1996), site <br /> conditions meet criteria for "low-risk" conditions qualifying the site for'No Further Action" status Benzene <br /> concentrations in soil and groundwater are below minimum detection levels, and hydrocarbon <br /> concentrations in groundwater do not pose a threat to human health or the environment Based on the <br /> feasibility analyses presented here, the most economical and cost-effective option is to apply"No Further <br /> Action"status to the site <br /> This report follows guidelines for Final Remediation Plans detailed in Appendix A of the Tri-Regional Board <br /> Staff Recommendations for Preliminary Evaluation and Investigation of Underground Tank Sites <br /> (CRWQCB-CVR, NC, SFB, 1991) <br /> 20 BACKGROUND <br /> 21 Site History <br /> The site is located on the corner of North Thornton and Walnut Grove Roads in Thornton, San Joaquin <br /> County, California (Figures 1 and 2) The site is a grass covered lot, encompassing approximately two <br /> acres with several concrete pads on the surface where former buildings were located The site was used <br /> as a small filling station and a restaurant from 1947 through 1956 During this period gasoline was <br /> distributed by two pumps located south of the concrete slab The pumps were supplied by two 1,000-gallon <br /> steel underground storage tanks (USTs) installed in 1947 and located in the southern UST pit shown on <br /> Figure 2 Remodeling of the service station occurred in 1956 and included the addition of four new gas <br /> pumps, relocation of the pumps to the eastern pump island location, installation of two additional <br /> 1 000-gallon USTs in the northern UST pit location (Figure 2) and removal of the former dispensers The <br /> new dispensers were supplied by all four USTs The service station ceased operation in 1975, at which <br /> time the dispensers were removed and the USTs were emptied The USTs located in the northern UST pit <br /> were removed by mistake in 1975 On June 2 1993 Wallace-Kuhl and Associates (Wallace-Kuhl) <br /> supervised the removal of USTs located in the southern UST pit (Wallace-Kuhl, 1993) Diesel fuel has <br /> historically never been dispensed on site <br /> 01a1FEA RPT(Wsc 15) <br /> FLUOR DANIEL GYI <br />