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SITE ASSESSMENT WORK PLAN Former ARCO Station No. 443 2478 East Oak Street, Stockton, California SJCEHD Site Code: RO-1781 1.0 INTRODUCTION On behalf of the Atlantic Richfield Company(ARC, a BP affiliated company), Broadbent&Associates, Inc. (Broadbent) has prepared this Site Assessment Work Plan (Work Plan)for the Former ARCO Station No. 443, located at 2478 East Oak Street in Stockton,California (Site). On March 18, 2013, Broadbent met with officials from San Joaquin County Envrionmental Health Department(SJCEHD). During this meeting,SJCEHD officials had recommended evaluating the risks resulting from the potential vapor intrusion to current or future occupants of the onsite building. Additionally,the SJCEHD expressed a concern regarding the integrity of the data obtained from the monitoring well MW-8. An 85-feet section of an 18-inch auger was left in place in the annulus between the augers and the conductor casing during the well installation. It was recommended to consider proper destruction of MW-8 and install a new well adjacent to it. This Work Plan presents a scope of work to address the above recommendations. The Work Plan includes a brief Site description,summary of previous environmental activities, proposed scope of work, and anticipated schedule for completion of the proposed tasks. 2.0 BACKGROUND INFORMATION 2.1 Site Location The Site is located at the northwest corner of North Filbert Street and East Fremont Street in Stockton, California,and is currently developed with commercial businesses, asphalt-paved parking,and landscaped areas along its boundaries. The northwest portion of the Site is covered with unpaved gravel. A Site Location Map is provided as Drawing 1. A Site Plan with proposed sample locations is provided as Drawing 2. 2.2 Previous Environmental Activities at Site In 1975,the former service station on the Site was closed and the property was sold. The new owner had reportedly agreed to remove the underground storage tanks(USTs)at the Site but there are no records that confirm the UST removal. A total of 45 soil borings and ten groundwater monitoring wells were installed at the adjacent Shell station after an unauthorized release was reported in 1997(Stantec, 2013). Investigations conducted by Cambria Environmental Technology on behalf of Shell in 2002 and 2005 included advancement of soil borings at the Site and had indicated presence of petroleum hydrocarbons in the soils and groundwater at the Site. Specifically, petroleum hydrocarbons were detected between 20 and 70 feet samples in SB- 26 that was advanced near the former onsite dispenser island (Stantec,2013). However, no analytes were detected in SB-27 that was advanced relatively farther from the location of former dispenser islands. Petroleum hydrocarbons were detected in groundwater at both these locations. The 2005 investigation indicated that two separate plumes of gasoline range organics(GRO) and 1,2 dichloroethane(1,2 DCA)dissolved in groundwater were present;one beneath the Shell Station and the other beneath the Site. The 2010 additional investigations conducted on behalf of Shell confirmed the presence of separate groundwater plumes beneath the two sites with little or no commingling.