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1 <br /> I <br /> Mr. Michael 0 <br /> October 166,, 2008 <br /> 020088 <br /> CONESTOGA=ROVERS <br /> & ASSOCIATES <br /> The plume at the site appears to be stable and primarily contained on site. We have sentry wells between <br /> the site and the off site domestic wells that show no plume migration toward the domestic wells. Site <br /> perimeter wells also indicate the plume is stable and not moving offsite. We will continue to monitor <br /> gasoline constituent concentrations in perimeter wells to verify plume stability. Additionally, hydraulic <br /> gradient at this site is typically very flat, which is likely why the plume is primarily contained on site. <br /> In summary, the delays associated with obtaining a new permit for batch discharge, the limited space (for <br /> water storage), and the low production volume for batch discharge make this option of little benefit. <br /> Time would be better spent moving forward with the ISCO option. <br /> Insitu Chemical Oxidation <br /> ISCO involves injecting oxidizing agents into the subsurface to destroy localized high concentrations of <br /> organic compounds, in this case fuel related compounds. The conceptual design for ISCO treatment at <br /> this site would involve installing 12 injection wells in the southern portion of the site (the area with the <br /> highest concentration of gasoline constituents in groundwater). These wells would be used for the <br /> injection of the oxidizing agent (most likely a sodium persulfate solution and a hydrogen peroxide <br /> solution). We estimate that quarterly injections of the oxidizing agents would be necessary over a 1 to 2 <br /> year period. Bench scale testing will likely be necessary and obtaining an injection permit from the <br /> Regional Water Quality Control Board will likely also be necessary. We anticipate permitting, testing, <br /> and well installation activities will take several months to complete. Once these activities are complete, <br /> chemical oxidation injection can begin. <br /> 240783 3 <br /> Worldwide Engineering, Environmental, Construction, and IT Services <br />