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S ECC R - - - 7-Eleven Store #14117 Corrective Action Plan October 12, 2007 Page 4 REMEDIAL APPROACH Oxygen injection is used to stimulate the biodegradation of gasoline-range petroleum hydrocarbons and oxygenates dissolved in groundwater. Past studies on subsurface bacterial colonies at the site (Site Conceptual Model, Shaw Group, June 20, 2002) indicate that indigenous populations of bacteria are present in-situ, and are capable of intrinsic biodegradation. Based on the favorable results of the oxygen injection feasibility study conducted in December 2005, the SJCEHD has approved the initial IRAP submitted by SECOR in April 2004 (Attachment A) which proposed oxygen injection as a remedial approach. While TBA is no longer considered the primary contaminant of concern at the site, SECOR proposes moving forward with the installation of additional oxygen injection wells as proposed in April 2004 based on the following: • As noted above, historical data indicate that subsurface indigenous bacterial colonies are present in-situ, and are capable of intrinsic biodegradation of hydrocarbons • Based on the favorable results of the oxygen injection feasibility study conducted in December 2005, the SJCEHD has already approved the initial IRAP which proposed injecting oxygen injection into the subsurface • The continuous sand unit at approximately 20-25 feet bgs provides ideal conditions to disperse the injected oxygen • Current concentrations do not indicate a significant contaminant mass that would hinder the effectiveness of oxygen injection as a remedial approach • The site is particularly small in size which limits options for more complex remedial approaches (i.e. extraction system components, holding tanks, etc.). ADDITIONAL WELL INSTALLATION SECOR proposes to install of four additional oxygen injection wells (1-2 through 1-5) at the locations shown in Figure 2. Site Specific Health and Safety Plan and Utility Clearance SECOR will modify the existing site-specific Health and Safety Plan (HASP) for well installation activities proposed at the site as required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 CFR 1910.120). The document will be reviewed and signed by all SECOR personnel and subcontractors performing work at the site. Permitting and Utility Location SECOR will obtain well permits from SJCEHD prior to initiating work. Prior to conducting subsurface work at the site, Underground Service Alert (USA) will be contacted to delineate subsurface piping near the site with surface markings. In addition, a private utility locator service will be contracted to clear the area surrounding the proposed well locations. 14117 CAP 10-12-07.doc SECOR Intemational, Inc.