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+ k <br /> 2905 West Benjamin Holt Drive, Stockton, California March 16, 1994 <br /> Chevron U.S.A. Products Company Page 18 <br /> 6.0 CONCLUSION <br /> The results of environmental assessment at the Chevron service station located at 2905 West Benjamin <br /> Halt Drive in Stockton, California indicate that soil and groundwater have been impacted by <br /> gasoline-range hydrocarbons released from the former UST complex-located in the southern portion of <br /> the site. Evaluation of data collected in past environmental investigations has defined the northern, <br /> western and eastern boundaries and vertical boundaries of hydrocarbon-impacted soil and groundwater <br /> related to the Chevron site. Southern extent of hydrocarbon-impacted material is undefined due to the <br /> presence of material impacted from past unauthorized releases from the ARCO station. Based on the <br /> boundaries of impacted soil and groundwater, no immediate risk is apparent to the local water supply. <br /> Four proposed alternatives for corrective action have been proposed and include source removal, <br /> isolation, and groundwater monitoring and sampling, bio-sparging, soil vapor extraction, and air sparging <br /> with soil vapor extraction. Based on the technical and economic evaluation presented in the report the <br /> following relative ranking matrix has been developed to summarize the analysis of each alternative. <br /> Technologic evaluation is based on the ease of implementation (1 = easiest, 4 = most difficult) and the <br /> ..• hydrocarbon removal rate (1 = most rapid removal, 4 = slowest removal). Economic evaluation is <br /> based on the capital costs (1 = lowest capital cost, 4 = highest capital cost) and operating costs <br /> (1 = lowest operating costs, 4 = highest operating costs) over the lifecycle of the project. A ranking <br /> according to the above parameters is listed below. <br /> Corrective Action Alternative Comparison <br /> Corrective Action Implementation Removal Rate Capital Costs Operating Cost <br /> Alternative <br /> Source Removal/ 1 4 1 1 <br /> Isolation <br /> Soil Vapor 3 2 3 3 <br /> Extraction <br /> Air Sparging 4 1 4 4 <br /> Bio-Sparging 2 3 2 2 <br /> 5073PA RAPT <br /> GROUNDWATER <br /> TECHNOLOGY <br />