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1 McDowell & Davis Towing Quarterly Groundwater Sampling Report November 2001 Page: 2 �..r 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 November 20, 2001. Groundwater Elevations 11-20-01 Wel! lCollar Elevation DTW GW Elevation MW-1 118.14 63.09 55.05 MW-2 118.79 63.31 55.48 MW-3 118.39 63.68 54.71 Groundwater flow was to the southeast with a very shallow gradient (0.014 ft/ft). The potentiometric surface and groundwater flow direction are shown on Figure 2 Site Map / Groundwater Flow. Laboratory analysis were reported non detectable concentrations (<0.05 mg/1 gasoline, <0.3 ug/l benzene, <0.3 ug/1 Toluene, <0.3 ug/1 ethyl benzene, <0.6 ug/1 xylenes, and <1.0 ug/1 MTBE. All other oxygenates were also reported as not detected. The dissolved oxygen concentrations show a very slight variation (6.6 to 7.8) and an overall increase in concentration compared to past monitoring events which indicates that limited biologic activity in the area of the soil contamination. The increase and slight variations in dissolved oxygen concentrations suggests that that the release has not caused a significant groundwater impact. Laboratory Groundwater Sample Results { ) Sample LD. Gasoline Benzene Toluene E-Benzene XylenesOxygenates 01 MW-1 <0.05 <0.3 <0.3 <0.3 <0.6 ND 7.8 MW-2 <0.05 <0.3 <0.3 <0.3 <0.6 ND 7.4 MW-3 <0.05 <0.3 <0.3 <0.3 <0.6 ND 6.6 ND=Non Detect NA-Not Analyzed MgIL for gasoline µg/L for BTEX,MTBE,and 8260 Oxygenated Compounds Gasoline and gasoline constituents were not detected in any of the monitoring wells in the November 2001 monitoring event. Previous monitoring events have detected gasoline and gasoline constituents 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. Additional monitoring of the existing wells should be conducted to confirm the degradation of groundwater contaminants detected in previous monitoring events. 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 prior to closure of the site.