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George's Service Remedial Action Work Plan Project No.425.2 June 30,2011 In the same letter dated October 16, 2008, SJCEHD also approved advancing 15 GeoProbes®and collecting soil and groundwater samples to further define the distribution of the contaminant mass. SJCEHD stated that they would not comment further on the Advanced ORC injection proposal until the results of the GeopProbe® Investigation were reviewed. GTI prepared an Additional Site Characterization & Revised Site Conceptual Model dated June 7, 2010 (and which was revised January 26, 2011) which summarized the GeoProbe investigation conducted at the George's Service Site from January 5 —January 8, 2010. In a letter dated June 10, 2011, SIC EHD concurred with the recommendations of GTI's ASC & Revised SCM Report, and suggested that sparge wells be installed in the former UST over-excavation backfill to accelerate remediation of groundwater. SIC EHD directed that a RAP be prepared and submitted to EHD before August 1, 2011. The following remedial action plan summarizes the activities proposed for the Georges Service Site. 3. SITE INVESTIGATIONS The various investigations, reports and work plans have been summarized above. The suspected source of the gasoline release at the Site is from the former USTs associated with the George's Service automobile repair facility and market. After the USTs were removed from the Site, further soil, soil gas and groundwater investigations were performed during several phases of investigation and remediation. Groundwater monitoring wells were installed in April 1995, and ongoing groundwater monitoring at the site commenced. In 2002, GTI performed a removal action as discussed below. A pilot test study was conducted at the Site from July 6 — July 9, 2009 and the reported concentrations in the soil gas indicated that soil vapor extraction is a viable method to remediate this Site. Refer to Soil Vapor Extraction Pilot Test Report — George's Service, 1600 Durham Ferry Road, Tracy, California prepared by GTI,dated August 26, 2009. Historical soil analytical data is included in Table 10 of Appendix A, and a summary of groundwater monitoring data is included in Tables 2 through 9 of Appendix A. 3.1. Regional Structure George's Service (Georges) is located in the northeast quarter of Section 20, T3S, R6E, related to the Mount Diablo B&M, on the United States Geological Survey (USGS) Topographic Map, Vernalis Quadrangle, California, 7.5 minutes series. A review of the USGS Topographic Map reveals that the elevation of this Site is approximately 83 feet above mean sea level (AMSL). A vicinity map for this Site is included in Figure 1. Geological Technics Inc. 4 4252 RAP.docx