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• 15 April 2004 AGE-NC Project No 99-0559 Page 4of13 22 OFF-SITE ASSESSMENT In September and October 2002, five additional, paired soil bonngs (CPT-4 to CPT-8) were advanced off-site(Figure 2) TPH-g was detected in ground water samples collected from HU2,HU4 and Upper HU5 of the off-site soil borings, the maximum concentration was 2,000 µg/1 in HU4 In addition, BTEX compounds were detected in HU2 Fuel additives were detected in all hydrologic units The highest concentrations were detected in HU4, MTBE was detected in HU4 at a maximum concentration of 2,600 µg/I, ETRE and TAME were detected at 25 µg/1 and 5 6 µg/l,respectively,and TBA and DIPE were detected at 630µg11 and 18 µg/l,respectively However,only TBA was present in Lower HU5,at a concentration of 180µg/1 Dissolved MTBE extends off-site past all current sampled locations The concentrations of dissolved MTBE decreased away from the site, except to the west at CPT4, where the highest concentration of off-site MTBE was detected The solvent TCE was detected in HU2 and HU4 In the off-site borings CPT-5 and CPT-8 (Figure 2),at a maximum concentration of 1,700 µg/1 The TCE appears to originate from an off-site source, since TCE was not detected in CPT borings (e g , CPT-4 and CPT-6) closer to the site i i The vertical extent of dissolved TPH-g,benzene and MTBE does not extend to below 130 feet bsg 3 0. INTERIM GROUND WATER REMEDIATION SYSTEM Ground water remediation system installation and operation were performed in accordance with procedures descnbed in the approved Interim Remediation and Site Assessment Work Plan, dated 25 January 2001 and Interim Remediation Work Plan -Addendum, dated 16 September 2002 A remediation enclosure and fencing for the ground water treatment system was installed on 18 and 19 February 2003 Ground water remediation equipment was delivered at the site on 26 February 2003 Between 11 March and 15 April 2003 an associated piping network was Installed at the site On 01 and 02 April 2003, four ground water extraction wells were installed at the site The dedicated electncal service was installed on 10 April 2003 The interconnection for the ground water recovery and treatment system were Installed and Inspected between 05 May and 26 May 2003 Advanced GeoEnviron mental,Inc