SITE INFORMATION AND CORRESPONDENCE

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Stantec Interim Remedial Action Plan Former ARCO Service Station No. 443 July 10, 2008 1.0 Site Information and Background This work plan has been prepared by Stantec Consulting Corporation (Stantec) on behalf of Atlantic Richfield Company (ARC), a BP Affiliated Company, in response to the letter from the San Joaquin County Environmental Health Department (SJC/EHD) dated June 2, 2008 (Attachment A). This document presents a work plan to install four groundwater monitoring wells and perform monthly vacuum truck interim response activities at Former ARCO Service Station No. 443 (site). The purpose of the groundwater monitoring well installation is to obtain lateral and vertical delineation of the presence of hydrocarbons. The purpose of the monthly vacuum truck interim response activities is to reduce the on-site presence of hydrocarbons. This work plan presents a brief site description, a summary of previous site assessments, and a detailed scope of work. The site is located at the northwest corner of East Fremont Street and North Filbert Street in Stockton, California (2478 East Oak Street). The site previously had an address of 2491 Fremont Street. The site is currently developed with commercial businesses, asphalt paved parking, and landscaping along the borders of the property. According to the United States Geological Survey (USGS) topographic map dated 1987, the elevation of the site is approximately 23 feet (ft) above mean sea level on relatively flat terrain. North Filbert Street bounds the site to the east, East Fremont Street to the south, and East Oak Street to the north. Commercial businesses are present east and south of the site and residential properties are located north and west of the site. An active Shell Service Station (2494 East Fremont Street) is located south of the site. Environmental investigations are currently being conducted at this location and groundwater monitoring and sampling are coordinated with both sites. The nearest open body of water is the Stockton Diverting Canal, located approximately 1.1 miles northeast of the site. 1.1 Site History and Previous Investigations The site was utilized as an ARCO Service Station from at least 1958 until at least 1975. The site consisted of one building in the central portion of the site and two dispensers on the eastern and southern portion of the site. In March 1975, the site was sold and closed. According to the SJC/EHD, during the purchase of the property the new owner agreed to pull the underground storage tanks (USTs). The site file did not contain any information related to the UST location or removal of the USTs from the site. According to ARC UST data inquiry service, the site formerly dispensed gasoline from three 4,000-gallon USTs. The site also utilized one 280- gallon tank and a Corning 6-M tank. The purpose and/or use of the two tanks were not provided in the documents. The Shell-branded Service Station located across Fremont Street from the site had an unauthorized fuel release. Since the initial assessment started in 1998, a total of 29 soil borings and ten on-site groundwater monitoring wells have been advanced and installed. As part of the off-site assessment work, soil boring SB-18 located along the southern ARCO property boundary was drilled during assessment activities associated with the Shell Station in 2002. These results are presented in the Site Investigation Report prepared for the Shell Station by Cambria Environmental Technology, Inc of Roseville, California (Cambria) (Cambria, January 27, 2006). Soil samples collected from SB-18 at 60, 70, and 80 ft below ground 1 443 IRAP.doc