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encountered. Soil samples were collected from borings B2, B3,and B5 for laboratory analyses. Petroleum
<br /> hydrocarbon concentrations were not detected in the soil samples(Terra Vac, 2004).
<br /> On June 8, 2006, Terra Vac performed a baseline soil assessment prior to temporary closure of the USTs
<br /> and lease termination. Three soil borings(131-06, 132-06,and 133-06)were advanced to 45 feet bgs. Results
<br /> of the soil sampling indicated concentrations of up to 452 mg/kg TPH, 1.97 mg/kg benzene, and 0.128
<br /> mg/kg MTBE. Based on the decreasing trend of petroleum hydrocarbon constituents observed in soil,
<br /> Terra Vac concluded a new release of gasoline had not occurred (Terra Vac, 2006).
<br /> In December 2007, GeoHydrologic Consultants, Inc. (GHC) performed oversight of the UST removal, well
<br /> and piping removal, and soil sampling activities conducted at the site. Three 12,000-gallon USTs,
<br /> associated fuel lines, and three dispenser islands were removed from the site. Soil sample results for the
<br /> samples collected from beneath the gasoline USTs, fuel lines, and dispensers did not indicate detectable
<br /> concentrations of petroleum hydrocarbons. The related conveyance piping from MW-3,VW-4, and MW-
<br /> 10/VW-1 in the proximity of the excavation areas was disconnected, severed, and removed. The existing
<br /> lines inside of the proposed excavation areas were cut back and capped to prevent damage and plugging
<br /> of the conveyance lines. Groundwater monitoring well MW-12 and dual nested wells MW-11/VW-3 and
<br /> VW-2 were properly destroyed by over-drilling the depth of the wells. Following the tank removal and
<br /> well destruction activities, GHC supervised the installation of replacement wells for MW-11/VW-3 and
<br /> MW-12 in January 2008. At the direction of the SJCEHD, VW-3 was reportedly installed in a separate
<br /> borehole approximately three feet southwest of well MW-11R. Replacement wells MW-11R, MW-12R,
<br /> and VW-3 were installed in the UST area. After UST removal activities, soil samples were collected from
<br /> beneath the USTs (UST1N-20.5, UST11VI-21.5, UST1S-21, UST2N-20, UST2M-21.5, UST2S-21, UST3N-20,
<br /> UST3S-20, UST3M-22, and UST3M-N-21), piping (P-1-15, P-1-35, P-1-55, and P-1-75), and dispensers (D1-
<br /> 10, D2-10, D3-10) using direct-push or hollow-stem auger methods(GHC, 2008a).
<br /> Complete references for activities performed prior to 2009 can be found in Stantec's Site Conceptual
<br /> Model dated October 23, 2009.
<br /> In preparation for pending site redevelopment activities, in October 2010, Stantec destroyed wells MW-
<br /> 4, MW-10, MW-11R,VW-1,VW-3,VW-4(A,B,C),VW-5(A,B,C),and VW-6(A,B,C)and protected wells MW-
<br /> 3, MW-7, and MW-12R in accordance with Stantec's Addendum to July 8, 2010 Work Plan for Monitoring
<br /> Well Destruction and Replacement, and Additional Path Forward, dated September 23, 2010 (approved
<br /> by the SJCEHD on October 1, 2010). Well destruction and protection activities are documented in
<br /> Stantec's Well Destruction and Well Protection Report, dated March 15, 2011.
<br /> In May 2011, ATC Associates Inc. (ATC) supervised the recovery of previously protected wells MW-3,
<br /> MW-7, and MW-12R, and the installation of monitoring wells MW-4R and MW-13 through MW-16. The
<br /> work was performed in accordance with ATC's Letter Addendum to Stantec's Addendum to July 8, 2010
<br /> Work Plan for Monitoring Well Destruction and Replacement, and Additional Path Forward, dated April
<br /> 13, 2011. Results of the well installation activities are documented in ATC's Monitoring Well Installation
<br /> Report, dated July 22, 2011.
<br /> In February 2012, ATC supervised the installation of on-site groundwater monitoring wells MW-17 and
<br /> MW-19 through MW-22, vertical delineation soil boring SB-1, and the collection of shallow soil vapor
<br /> samples SV-1 through SV-5. The results of the site assessment activities were presented in Cardno ATC's
<br /> (aka ATC)Additional Site Assessment Report, dated July 30, 2013.
<br /> On October 15 and 16, 2014, Cardno ATC supervised the installation of three soil vapor wells (SVE-1
<br /> through SVE-3) and one air sparge well (AS-1) at the site. The work was performed in accordance with
<br /> Cardno ATC's Workplan For An AirSparge/Vapor Extraction Pilot Test, dated July 11, 2014. On January 5
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