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y StantK • <br /> Site History and Previous Investigations <br /> Former ARCO Service Station No. 2168 <br /> February 16, 2010 <br /> Rio Vista, California (Woodward) by over-drilling. Due to the presence of utilities, VW-6 was <br /> destroyed on September 28, 2005 by pressure grouting. <br /> From November 3, through -15, 2005, Woodward installed four groundwater monitoring wells <br /> (MW-9 through MW-12) to further define the lateral extent of petroleum hydrocarbon-impacted <br /> groundwater beneath the site. Seventeen dual-completion SVE/air sparge (AS) wells (EW- <br /> 1/SP-1 through EW-17/SP-17) and five AS wells (SP-18 through SP-22) were installed to <br /> complete the treatment system well network at the site. <br /> URS Corporation of Sacramento, California (URS) excavated trenches, laid and connected <br /> tubing to the AS wells and the injection system, and conducted general system installation. <br /> URS began trenching activities on December 16, 2005 and in an effort to coordinate with <br /> construction of the car wash, URS suspended installation activities on December 19, 2005. <br /> URS returned to the site on February 20, 2006 and completed the system installation on August <br /> 25, 2006. The system was started on October 17, 2006 following the collection of carbon <br /> dioxide readings. The treatment system was installed without any changes to the original <br /> design. <br /> 2168 Site History and Previous Investigations.doc 2 <br />