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Ms.Amy Terrell <br /> April 27,2010 <br /> Page 7 of 10 <br /> • TON—MW-5 <br /> Dissolved phase TON was observed to be 3 mg/L. This concentration is below the MCL of 10 <br /> mg/L. Although TON concentrations have consistently been below the MCL of 10 mg/L <br /> since the 2007 injection event, the overall TON concentration trend appears to be increasing. <br /> • 1,2,3-TCP—MW-5 <br /> Dissolved phase 1,2,3-TCP was observed to be 0.15 µg/L. This concentration is greater than <br /> the California Notification Level of 0.005 µg/L. There has been no significant change in <br /> 1,2,3-TCP concentrations since the 2007 injection event. <br /> • 152-DCP—MW-5 <br /> Dissolved phase 1,2-DCP was observed to be 9.3 µg/L. Dissolved phase 1,2-DCP <br /> concentrations have fluctuated over time, with an overall decreasing trend since 2005. This <br /> concentration exceeds the MCL of 5 µg/L. There has been no significant change in 1,2,3-TCP <br /> concentrations since the 2007 injection event. <br /> • EDB—MW-5 <br /> Dissolved phase EDB was observed to be 0.11 µg/L. This concentration exceeds the MCL of <br /> 0.05 µg/L, but is below the background EDB concentration of 0.26 gg/L (Geosyntec, 1998). <br /> EDB concentrations slightly increased subsequent to the 2007 injection; however, EDB <br /> concentrations were observed to be below background concentrations during the Third <br /> Quarter 2009 and First Quarter 2010 groundwater sampling events. <br /> OA/OC Review <br /> The analytical data reports were reviewed for completeness, accuracy, conformance with holding <br /> times and detection limits were within acceptable limits. Based on the review, ATC believes the <br /> reported data is of acceptable quality for purposes of this report. <br /> SUMMARY OF REMEDIAL ACTIVITIES <br /> Summary of Initial 2002 Field-Scale Pilot Test <br /> In June 2002, Hydrogen Release Compound (HRC®) was injected into the first-encountered <br /> groundwater zone at 28 locations in a test plot in the near vicinity of well MW-2. The HRC® was <br /> injected as part of a field-scale pilot test to evaluate the efficacy of HRC® in degrading chlorinated <br /> hydrocarbons (i.e. pesticides) and TON in groundwater at the Site. <br /> Summary of 2007 Expanded Pilot Test <br /> Five years after beginning the Initial Remediation Pilot Study, Geosyntec recommended expanding <br /> the pilot test to include additional injections and to use a more viscous, slow-release formulation <br /> (HRC-X®) of the HRC® utilized in the Initial Remediation Pilot Study. Geosyntec subsequently <br />