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02 May 2013 AGE-NC Project No. 99-0559 Page 4 of 5 4.0. CONCLUSIONS Based upon the results of the groundwater monitoring, AGE presents the following conclusions: The depth to groundwater has remained stable. Groundwater depth at the site during the semi-annual fourth quarter 2012 monitoring event showed a small increase within a shallow flow gradient, likely attributed to the ongoing groundwater extraction treatment. The groundwater elevation in wells monitored in Hydrogeologic Units 1 and 2 were similar and displayed the groundwater flow direction towards the remediation area surrounding the former UST release; HU3/4 displayed the groundwater flow direction southeast. The MTBE plume near the former UST area has generally declined in concentration since the March 2012 monitoring event; compared to the core of the plume that was extremely resistant to decline for several years through active groundwater and soil remediation. The dissolved MTBE plume in first water table wells extends southwest of the UST release; increases in concentration at wells MW-4, MW-5A; and declines at well MW-12 (off-site). MTBE continues to be non-detect below the laboratory detection limit in well MW-1. TBA was detected at well MW-3, MW-4 and MW-5A at nearly equal concentrations (averaging approximately 1,050 pg/I). MTBE has been detected in wells MW-5B, MW-7B and MW-11 at a depth of 100 feet bsg. The lateral extent of shallow, impacted groundwater towards the west and southwest, down-gradient of the UST area, has been defined. However, elevated concentrations of dissolved MTBE have migrated off-site, at a depth of approximately 100 feet bsg. The vertical extent of impacted groundwater at the former UST area has been defined. Historically, the vertical extent of dissolved plume is defined southwest of the USTs by wells MW-5E and MW-9, and further southwest of the site by well MW-10. TPH and BTEX plumes extend to deeper HUs near the property boundary at well MW-7; yet were not detected in well MW-5 at significant concentrations. Generally, concentrations of TPH-g, BTEX and MTBE in the most impacted shallow wells have been significantly remediated; the current concentration is 90% less than the typical concentration and the current concentration is 99% less than the maximum concentration. Advanced GeoEnvironmental, Inc.