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19 October 2012 <br /> AGE-NC Project No. 97-0312 <br /> Page 14 of 22 <br /> in July 2002 and in UST-5 until February 2003, when concentrations permanently <br /> decreased below laboratory detection limits. TPH-d was detected sporadically in wells <br /> MW-2, MW-3, MW-4, and MW-6 until as late as May 2003. BTEX constituents were <br /> detected consistently only in well MW-5, with a maximum concentration of 840 pg/1 <br /> (benzene, March 1998), in December 2003. These detections of TPH and BTEX generally <br /> corresponded with high groundwater levels, near 55 feet bsg. <br /> Currently (2011 ) no monitoring well have detectable concentrations of TPH-g. TPH-g and <br /> 1,2-DCA have been the only contaminants of concern reported above laboratory detection <br /> limits in MW-5 since March 2004; TPH-g was detected occasionally at concentrations of <br /> approximately 200 pg/I, and 1,2-DCA was detected at concentrations between <0.5 and <br /> 200 pg/I. Well MW-4 has remained non-detect since June 2001, well MW-7 has remained <br /> 6-0 non-detect since December 2002, well MW-3 has remained non-detect since May 2003, <br /> well MW-2 has remained non-detect since March 2004, and no constituents of concern <br /> were detected in MW-8 and MW-9 during previous quarterly monitoring events and during <br /> 6.d the most recent event in 2011. <br /> Based on the April 2006 CPT investigation, the lateral and vertical extent of the 1,2-DCA <br /> plume is defined. Down-gradient, the 1,2-DCA plume does not extend to CPT-2, while <br /> MW-6 reported occasional low concentrations of 1,2-DCA. Vertically, the 1,2-DCA plume <br /> does not appear to extend to 100 feet bsg (MW-9). The detections of dissolved 1,2-DCA <br /> .r in MW-5 have decreased since June 1999 when the concentration was 1,100 pg/I. AGE <br /> previously estimated that approximately 0.14 pounds (lbs), or 0.013 gallons, of 1,2-DCA <br /> remain in site groundwater. <br /> The lateral extent of dissolved petroleum hydrocarbon contamin tion/in shallow <br /> groundwater was pr iously defined east of well MW-5 by monitoring w MW-8, northwest <br /> of MW-5 by MW-2, and south (up-gradient) of well MW-5 by MW-4 The down-gradient <br /> extent of dissolved TPH/BTEX is defined 150 feet north (down-gradient) of well. Based on/ <br /> the analytical results of the groundwater samples collected from wells MW-7,/�nd MW-9, <br /> the vertical extent of petroleum hydrocarbon-impacted groundwater at the site is defined. <br /> tAV?�, {,�d N E ; to,We 111 4.,-,1 J IJPC- ey KW4 (t,2 UA I---) -6V <br /> Current analytical results of groundwater monitoring well samples collected during April <br /> 2012 and historically limit the impacted groundwater to the area beneath the former UST <br /> at well MW-5 and the dispenser area. <br /> Drinking water at and near the site is supplied by a commercial, domestic well. Two <br /> domestic wells, designated DW-L (large) and abandoned DW=S (small); are located near <br /> the site; DW-L is located approximately 200 feet northwest of the site and DW-S is located <br /> approximately 150 feet west of the site. <br /> Advanced GeoEnvironmental,Inc. <br /> u <br />