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04 April 2001 AGE-NC Project No 95-0144 ' Page 6 of 9 I ' MTBE was detected in one soil sample analyzed from boring 15B-12-20 at a concentration of 96 micrograms per kilogram(pg/kg) Figures 4, 5 and 6 illustrate the approximate extent of petroleum hydrocarbon contamination in soil in the area of the clarifier Analytical results of soil samples are summarized on Tables 2 and 3 The laboratory report (MAI Lab IDs 53617 through 53627) and chain-of-custody forms are included in Appendix C ' 3 3ANAL C YTI AL RESULTS OF GRAB GROUND WATER SAMPLES ' TPH-g was detected in grab ground water samples analyzed from 1513-10, 153=12 and 15B-13 at concentrations of 1,500 micrograms per liter (gg/1), 4,800 gg/l and 280 gg/l, respectively TPH-d ' was detected in each grab water sample at concentrations ranging from 570,000 µg/l(15B-12W) to 1,600 gg/l (15B-13W ) TPH-mo was 'detected in samples analyzed from each boring at concentrations ranging from 130,000 gg/l to 870 gg/l Benzene and toluene were detected in grab ground water samples analyzed from soil boring 15B--12 at concentrations of 8 6 gg/l and 9 7 gg/l,respectively Ethylbenzne was detected in three of the four ' • ground water samples at concentrations ranging from 3 8 gg/1 to 0 63 gg/l Xylenes were detected in grab ground water samples from soil probe borings 15B-12 and 15B-13 at concentrations of 24 gg/l and 0 36 gg/l, respectively The analytical results of the grab ground water sample are summarized on Tables 4 and 5 The laboratory report (MAI Lab IDs 53630 through 53633) and chain-of-custody forms are included in Appendix D ' 3 4 RELATIVE GROUND WATER ELEVATION AND GRADIENT The elevation of ground water in each well was calculated by subtracting the depth to water from the surveyed casing elevation (Table 1) Between August 2000 and November 2000, ground water elevation decreased between 0 64 feet and 1 65 feet in the twelve wells at the site The approximate Ihydraulic gradient for the November 2000 monitoring event was inferred to be 0 002 ft/ft with a northeast flow direction Ground water elevation contours derived from data collected on 28 November 2000 are depicted in Figure 3 Ground water was between approximately 0 02 and 5 41 feet above the screened interval in monitoring wells MW-1, MW-2, MW-4, MW-5, MW-8, MW-11, MW-12, MW-13 and MW-18 Ground water was within the screened intervals of MW- 19A, MW-20A and MW-21A Ground water elevations in nested wells MW-19, MW-20 and MW-21 were between 1 14 and 2 26 feet lower in deeper screened intervals beneath a potentially confining clay layer than in the shallower screened intervals Data from the upper screened intervals,established in first-encountered ground water, was utilized for gradient determination Advanced GeoEnvironmenfai,Inc