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30 July 1999 <br /> AGE-NC Project No 95-0143 <br /> Page 6 of 8 <br /> report(MAI Sample Nos 09301-09341 and 09758-09762) and chain-of-custody forms are included <br /> in Appendix B <br />' Petroleum hydrocarbons were not detected in soil samples collected from SWI, SW5, SW9 and <br /> VW 1, defining the western extent of impacted soil MW-16 and S W23 define the southern extent <br /> of Impacted soil Petroleum hydrocarbons were not detected during the installation of MW-10 and <br />' organic vapor was not detected in sampled from SW8 and SW20, defining the eastern extent of <br /> impacted soil Low concentrations of hydrocarbons were detected in SW2 and SW4, indicating that <br /> these borings are near the northern extent of impacted soil The center of the impacted soil plume <br />' is located near VW5 <br /> I3 3 GROUND WATER ELEVATION AND GRADIENT <br /> The elevation of ground water in each well was calculated by subtracting the depth to water from <br />' the surveyed casing elevation(Table 3) Between February and May 1999, ground water elevations <br /> increased an average of 0 83 feet During the May 1999 monitoring event, ground water was from <br /> 0 8 feet to 8 4 feet above the screened interval in each well The approximate hydraulic gradient was <br /> calculated to be 0 0016 ft/ftwith a northeasterly flow direction on the subject property Groundwater <br /> elevation contours for the May 1999 monitoring event are illustrated in Figure 7 <br /> 34 ANALYTICAL RESULTS OF WATER SAMPLES <br /> TPH-g was detected in the grab water samples collected from borings SW4, SW11, SW20 and SW23 <br /> at concentrations of 4,300 parts per billion (ppb, reported as micrograms per liter), 150,000 ppb, <br /> 1,100 ppb and 82 ppb, respectively BTEX were detected at concentrations as high as 27,000 ppb <br /> (toluene in SWI 1) Petroleum hydrocarbons were not detected in the grab water sample collected <br /> from boring SW9 Analytical results are summarized on Table 4 The laboratory report (MAI <br /> Laboratory I D Nos 09298-09300, 09756 and 09762) and chain-of-custody forms are included in <br /> Appendix B <br /> During the May 1999 monitoring event, TPH-g was detected in each well, except MW-10, at <br /> concentrations as high as 190,000 ppb (MW-3) BTEX compounds were detected in each well at <br /> concentrations as high as 50,000 ppb (toluene in the sample from MW-3) Benzene concentrations <br /> ranged from 1 1 ppb to 13,000 ppb Oxygenates were not detected at the site during the May 1999 <br /> sampling event <br /> The concentrations of hydrocarbons detected in MW-15, MW-16 and MW-17 were almost identical <br /> Only traces of hydrocarbons had previously been detected in 4 of the 42 samples collected from <br /> Advanced GQoEn%ironmental,Inc <br /> I <br />