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0 Sites). Aeration of soil containing volatile organic compounds (VOCs) is regulated by San Joaquin Valley Air Pollution Control District(SJVAPCD)4. Based on the anticipated involvement of local regulatory agencies and to provide initial cleanup criteria for the interim remedial action proposed in this workplan, interim cleanup criteria are based on review of Environmental Screening Levels (ESLs) established for soil, groundwater and soil vapor by the California Regional Water Quality Control Board, San Francisco Bay Region. These screening level guidelines are most appropriate for evaluation of site conditions. The ESLs are based on human health and ecological risk factors and considered to be conservative. Under most circumstances, and within certain limitations, the presence of a chemical in soil, soil gas or groundwater at concentrations below the corresponding ESL can be assumed to not pose a significant, long-term (chronic) threat to human health and the environment. Additional evaluation is usually necessary at sites where a chemical is present at concentrations above the corresponding ESL. Active remediation may or may not be required depending on site-specific conditions and considerations. Site specific clean-up goals will be based on anticipated future land use and formally established with regulatory oversight once the site conditions are further defined. 3.0 SITE DESCRIPTION The site is a roughly rectangular but irregularly shaped 1.92-acre property located on the northeast corner of El Dorado Street and Eighth Street in Stockton, California(Figure 1). It is a relatively flat, vacant parcel. The site surface consists of loose fill soil over most of the property with perimeter vegetation including several trees and bushes. California ground squirrel burrows were noted throughout the fill soil. ROKEN observed asphalt concrete along the western portion of the site, and underground storage tanks (USTs)were identified in the southwestern portion of the site. Several piles of material consisting of asphalt, soil, and concrete debris were also located near the UST area. The site is bounded to the north and west by commercial businesses, to the south by a neighborhood park and to the east by residential properties. A residential housing project is being considered for future development of the site. 4.0 BACKGROUND Current understanding of site subsurface conditions is based in part on investigation reports prepared by others(as referenced below) and from the results of a preliminary groundwater investigation performed by ROKEN. The following is a brief summary of these investigation findings: Krazan Associates (Krazan)completed a Phase I ESA and reported that the southern portion of the subject site appeared to have been occupied by a gasoline service station from at least 1938 until approximately 1970. No documentation was identified regarding the removal or abandonment of the USTs. Krazan reported a moderate potential for environmental impact to the site from past on-site operations that"potentially utilized Regulation IV—Prohibitions,Rule 4651 Soil Decontamination Operations(Adopted April 16, 1992),San Joaquin Valley Air Pollution Control District,Amended December 17, 1992;Amended September 20,2007. 5 Phase I Environmental Site Assessment,Vacant Land,2154 South El Dorado Street,Stockton,California,Project No. 114-06148,Krazan&Associates,Inc.,December 11,2006. 3