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lie 24 September 2004 AGE-NC Project No 97-0301 ' Page 5 of 6 • Generally, a steep downward vertical gradient was observed from wells MW-S,MW-9 and ' MW-12 and between the Second Water Zone, Third Water Zone and the Fourth Water Zone, nearly flat to very slight upward vertical gradient was observed between the First Water Zone ' and the Second Water Zone(Figure 3) • Analysis of ground water samples collected from MW-1 and MW-7 suggest the core of the plume Is impacted by TPH-g, BTEX and 1,2-DCA The core of the First Water Zone ' dissolved gasoline plume appears to be currently distributed near the location of wells MW-1 and MW-7, and contained within network of wells consisting of MW-2, MW-3, MW-4, MW-6, MW-9A, MW-10A, MW-11A and MW-12A(Figure 4) ' • Substantial concentrations of dissolved TPH-d and TPH-k have previously been detected in water samples collected from wells MW-1 and MW-7, indicating a limited distribution of 1 TPH-d and TPH-k in the area assessed BTEX and 1,2-DCA concentrations in ground water samples MW-1 and MW-7 were ' substantially above their respective Maximum Contaminant Levels in drinking water • Very low concentrations of MTBE,n,T1�ME, EDB and TBA have been detected at wells MW-1, MW-2, MW-3, MW-4, MW-6 and MW-7 indicating that there is only a minor ' . impact of these components • Based on one quarterly ground water monitoring event, the lateral and vertical extent of ' dissolved petroleum hydrocarbons appears to be limited to First Water Zone wells MW-1 and MW-7 at the site and approximately 50 feet north of the site 5.0. RECOMMENDATIONS 1 Based upon data collected during March 2004, AGE recommends ' • Continued ground water monitoring utilizing wells MW-1 through MW-12, the second quarter 2004 ground water monitoring event was performed on 17 June 2004 The third quarter ground water monitoring event is tentatively scheduled for 30 September 2004 ' • If applicable,conducting future ground water monitoring events concurrently with the Cal- Tank Lines site (3105 South El Dorado Street) -- Based on the entire set of data collected to date, additional ground water monitoring wells/soil borings are not warranted at this time and the existing monitoring well network may be sufficient ' to complete a site Corrective Action Plan (CAP) and/or Problem Assessment Report (PAR) ' Advanced GcoEnvironmentat,Inc