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McDowell & Davis Towing Quarterly Groundwater Sampling Report June 2001 Page: 2 SUMMARY FINDINGS Groundwater was present as an unconfined state at an approximate depth of 62 feet below ground surface at the McDowell & Davis Towing site on June 27, 2001. Groundwater Elevations 6-27-01 Well Collar Elevation DTW GW Elevation MW-1 118.14 61.81 56.33 MW-2 118.79 62.04 56.75 MW-3 118.39 62.42 55.97 Groundwater flow was to the northwest with a very shallow gradient (0.017 ft/ft). The potentiometric surface and groundwater flow direction are shown on Figure 2 Site Map / Groundwater Flow. Laboratory analysis were reported 0.87 to 2.4 mg/1 for gasoline and 110 to 8.5 ug/1 benzene, 350 to 46 ug/1 Toluene, 48 to 19 ug/l ethyl benzene, 130 to 43 ug/l xylenes, and 77 to 10 ug/l MTBE. All other oxygenates were reported as not detected. The dissolved oxygen concentrations shows a very slight decrease (6.2 to 5.8) in the down gradient direction which indicates that limited biologic activity in the area of the soil contamination. The minimal of increase in biologic activity in the area of the plume suggests that that the release has not caused a significant groundwater impact. Laboratory Groundwater Sample Results (06-27-2001) Sample I.D. Gasoline Benzene I Toluene E-Benzene Xylenes I Oxygenates 02 MW-1 0.87 8.5 46 19 43 10 6.1 MW-2 1.2 j9---j-6-0---29 93 10 6.2 MW-3 2.4 110 350 48 130 77 5.8 ND Non Detect NA=Not Analyzed Mg/L for gasoline µg/L for BTEX,MTBE,and 8260 Oxygenated Compounds Gasoline and gasoline constituents were detected in all three monitoring wells at concentrations that exceed established water quality goals. Gasoline and gasoline constituents were recognized in soil samples collected at depths of 15 and 25 feet in a boring in the vicinity of the former dispenser island. The extent of the groundwater plume, as detected in the current monitoring event, is undefined. The previous groundwater-monitoring event detected trace (<0.5 ug/1) toluene concentrations in two of the wells. Additional monitoring of the existing wells should be conducted to confirm the groundwater impacts detected in the June 2001 event. A survey of potential contamination plume receptors within 1,000 feet of the point of release should be conducted to identify potential impacts of the release. If potential receptors are not identified to the survey, groundwater monitoring should continue to verify plume stability and degradation.