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' 05 January 2004 AGE-NC Protect No 97-0333 ' Page 10 of 11 (A-E) and MW-8 (A) Generally, a moderate to significant MTBE increase was reported at ' wells MW-3 and MW-7 (A,B and E),conversely, significant decreases were reported from on-site wells MW-1 and MW-2 (Figures 8 and 9, Table 5) k ' • Low concentrations of off-site MTBE were detected from wells MW-12B • Concentrations of PCE and/or TCE have been detected in water samples collected from all ' well locations associated with the Rainwater Car Wash investigation Minor to significant PCE and/or TCE concentrations were detected in 43 of 46 ground water monitoring wells located in First Zone, Second Zone, Third Zone and Primary Aquifer Zone Aquifers ' (Figure 10, Table 4) The highest concentrations of dissolved PCE were detected in the samples collected from First Zone wells MW-2, MW-3, MW-4, from Second Zone wells MW-7C,MW-8(B-C),MW-9B and MW-10(B and C),and from Third Zone wells MW-7D ' and MW-8D at concentrations as high as 2,100 pg/1 (MW-4) • PCE and TCE are chlorinated solvents often associated with dry cleaning operations Based ' on the October 2004 PCE iso-concentration map in First Zone water (Figure 10), AGE interprets the PCE/TCE-plume to have originated from the dry cleaner's facility located immediately east of the Rainwater Car Wash lie 5.0 RECOMMENDATIONS Based upon data collected from the site,AGE recommends ' • Continued quarterly ground water monitoring and sampling of monitoring wells MW-1 through MW-13 ' • Continued ground water extraction (interim ground water remediation) from well EW-1 • The most intense MTBE-impact was reported in the ground water samples collected from monitoring wells MW-2 and MW-3 with MTBE concentrations as high as 17,000 µg11 Furthermore, based on the ground water monitoring data collected to date, well MW-3 appears to be outside the effective`capture zone'of EW-1 groundwater extraction activities ' Therefore,AGE recommends installing one additional ground water extraction well(EW-2) in the area near MW-3 to augment interim ground water remediation efforts, extracted ground water from well EW-2 would be routed to the existing ground water pump-and-treat ' system ' Generally,the core of the dissolved MTBE-plume appears to located in the First Zone Aquifer within the area of wells EW-1, MW-1, MW-2, MW-3, MW-6 and MW-7A, outside of the dissolved • MTBE-core area, only low to very low MTBE concentrations were detected on-site and off-site ' Advanced GeoEnviron mental,Inc