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2 G� Cardno®
<br /> January 17,2014 ATC
<br /> Eggiman Well Destruction Report Shaping the Future
<br /> feet bgs and 55 feet bgs contained only trace concentrations of TPHg, ethyl benzene, and/or xylenes. The soil
<br /> samples collected from borings MW1 and MW3 at depths of 35 feet bgs contained trace concentrations of xylenes
<br /> and TPHg, respectively. The samples collected from borings MW1 and MW3 at depths of 40 feet bgs did not
<br /> contain detectable concentrations of TPHg or BTEX. MTBE, t-amyl methyl ether(TAME), t-butanol (TBA), ethyl t-
<br /> butyl ether(ETBE), di-isopropyl ether(DIPE), 1,2-dichloroethane (1,2-DCA), or 1,2-dibromoethane (EDB)were not
<br /> detected in any soil samples collected from borings MW1, MW2, and MW3, though the detection limits were
<br /> elevated in the MW2 sample from 35.5 feet bgs due to the high concentrations of TPHg noted previously.
<br /> In July and December 2003, ATC conducted additional subsurface investigation activities at the site that included
<br /> cone penetration testing, advancing a soil boring (SB8), and installation of monitoring wells MW4 through MW7.
<br /> Petroleum hydrocarbons were detected in soil samples collected from the boreholes of MW5 and MW6, and in the
<br /> groundwater samples collected from MW4 through MW-7.
<br /> On November 17 and 18, and December 5 and 28, 2005, an ATC geologist supervised the advancement of five soil
<br /> borings, SB9 through SB13. The borings were advanced for the purposes of evaluating the horizontal extent of
<br /> petroleum hydrocarbon impacted soil and groundwater in the vicinity of the site. Details of these activities are
<br /> summarized in ATC's Summary Report of Additional Subsurface Investigation, dated July 12, 2006.
<br /> Between May 24 and June 8, 2007, an ATC geologist supervised the installation of monitoring wells MW8 through
<br /> MW1 1. MW8 and MW11 were installed off site to the northeast and north adjacent to 1139 and 1107 East Harding
<br /> Way, respectively, to evaluate the lateral extent of petroleum impacted groundwater downgradient of the subject
<br /> site. Details of these activities are summarized in ATC's Subsurface Investigation Report, dated November 19,
<br /> 2007.
<br /> Ozone injection was recommended as the preferred remediation option in ATC's Feasibility Study Addendum for
<br /> the Eggiman Property, dated January 9, 2009. To expedite the testing and installation process, the EHD requested
<br /> comparison of the site with other nearby remediation sites already using or approved to use ozone injection, on the
<br /> basis that similar soil stratigraphy and water chemistry could be expected to give similar results. This comparison
<br /> was presented in ATC's Site Geology Comparison, dated September 24, 2009.
<br /> Between May 24 and May 26, 2010, seven injection wells (OS1 s, OS1 d, OS2s, OS2d, OS3, OS4, and OS5)were
<br /> installed in five borings on site. On July 27 and 28, 2010, narrow trenches were excavated to a depth of
<br /> approximately six inches and 112" stainless steel piping was installed to connect the injection wells to the compound
<br /> location on the south face of the garage building on site. Details of these activities are summarized in ATC's
<br /> Remediation Well Installation Report, dated October 25, 2010.
<br /> On March 24, 2011, a cabinet-mounted ozone generator was delivered to the site and installed adjacent to the on-
<br /> site building. Ozone injection into OW1s, OW1d, OW2s, OW2d, and OW3 was initiated on April 1, 2011.
<br /> Connections to OW4 and OW5 were completed on April 4, 2011 and the injection cycle was expanded to cover all
<br /> seven points. Reduced petroleum hydrocarbon concentrations were reported in the groundwater samples collected
<br /> from the injection wells and most of the monitoring wells at the end of the pilot test on June 14, 2011, while
<br /> increased petroleum hydrocarbon concentrations were reported in the groundwater samples collected from MW1.
<br /> The reduced petroleum hydrocarbon concentrations associated with the groundwater sample collected from the
<br /> injection wells at the end of the pilot test suggest ozone injection was effective in reducing petroleum hydrocarbon
<br /> concentrations at these locations. No significant rebound effects were observed during the post remediation
<br /> monitoring performed on November 15, 2011. Details of these activities are summarized in ATC's Ozone
<br /> Treatability Pilot Testing Report, dated June 8, 2012.
<br /> In letters dated September 12, 2012 and February 22, 2013 respectively, the EHD stated the site was a candidate
<br /> for closure under the new Low Threat Closure Policy(LTCP)that had been recently adopted and implemented by
<br /> the State Water Resources Board and the CVRWQCB, and requested completion of a Case Closure Report for the
<br /> site.
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