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27 February 2004 • AGE-NC Project No 95-0141 ' Page 4 of 5 • At the time of the December 2003 ground water monitoring event, ground water elevations ' at the site ranged from 13 51 feet below MSL to 14 74 feet below MSL The shallow ground water was inferred to flow generally toward the east-southeast, at a gradient of 0 004 foot/foot while the deeper ground water zone was Inferred to flow generally toward the east- southeast,at a gradient of 0 003 foot/foot Wells MW-3 through MW-5 were"drowned",and likely did not yield samples fully representative of ground water conditions near the top of the saturated zone,where fuel hydrocarbons would be expected to have the greatest impact 1 • During the fourth quarter 2003,TPH-g was detected in ground water samples collected from six of the fifteen wells at the site at concentrations as high as 110,000 µg/l TPH-g-Impacted shallow ground water has been defined(Figure 5),however,the TPH-g-Impact to the deeper ground water zone has not been defined toward the east and to a lesser degree south and north (Figure 6) ' During the fourth quarter 2003, BTEX constituent was detected in five of the fifteen wells ground water wells The benzene concentrations In all five wells exceeded the DHS' Maximum Contaminant Level(MCL) for benzene In drinking water and the concentrations ' of toluene, ethylbenzene and total xylenes in well EX-1 were significantly above their respective MCLs However, the use of the shallow and deeper ground water In the region does not Immediately appear to be for domestic use • During the fourth quarter 2003, 1,2-DCA was detected In ground water samples collected from nine of the fifteen wells at the site at concentrations as high as 190 µg/l (EX-1) The detected concentrations of 1,2-DCA were above the MCL 1,2-DCA-Impacted shallow ground water has not been defined toward the east, and 1,2-DCA-Impacted deeper ground water zone has not been defined toward the south, east and north Again, the use of the ' shallow and deeper ground water in the region does not immediately appear to be for domestic use A map illustrating the approximate extent of 1,2-DCA in shallow and deep ground water Is presented In Figures 7 and 8 5.0. RECOMMENDATIONS Based on the results of this and previous investigations, AGE recommends ' Continued quarterly monitoring of the ground water monitoring network • Preparation of a work plan for interim remediation of petroleum hydrocarbon-Impacted ' ground water at the site and vertical definition of the dissolved hydrocarbons and additives • If necessary, completion of the ground water extraction feasibility pilot test proposed in the AGE-prepared Work Plan Addendum, dated 09 April 2002 ' Advaneed Geo Environmental,Inc 1