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P S 4 14 April 1998 P AGE-NC Project No. 95-0185 Page 3 of 4 3.2. LABORATORY RESULTS OF GROUND WATER SAMPLES TPH-d was detected in ground water samples collected from monitoring wells MW-1,MW-2,MW-3 and MW-4 at concentrations of 10,000 parts per billion (ppb, reported as micrograms per liter), 140 ppb, 570 ppb and 79,000 ppb, respectively. TPH-g was detected in the ground water samples from well MW-1 and well MW-4 at concentrations of 290 ppb and 500 ppb, respectively. BTE&X compounds were detected in samples collected from wells MW-1 and MW-4 at , concentrations as high as 1.1 ppb (benzene, MW- 4). MTBE was not detected b EPA method 8260m in the samples collected r Y p of ected from .he monitoring wells. Tert butanol was detected in the sample collected from wells MW-I at a concentration of 16 ppb. ' Analytical results of yt monitoring well ground water samples are summarized in Table 2 for analyses by EPA Methods 8015M and 8020, and in Table 3 for analyses by EPA Method 8260. The ' laboratory report (MAI Laboratory I.D. Nos. 82612 to 82615), and chain-of-custody form are included in Appendix B. 4.0. SUMMARY AND CONCLUSIONS ' The following conclusions were drawn from the results of this investigation: • Ground water elevations have increased 0.6 and 0.09 feet.in monitoring wells MW-3 and MW-4, and have decreased 0.04 feet in monitoring wells MW-1 and ]AW-2, since the last quarterly monitoring event. • Concentrations of TPH-g and BTE&X hydrocarbons have fluctuated over a wide range in MW-I and MW-4, and have increased slightly in MW-2 and MW-3. • Well MW-2 appears to be located at the southern edge of the dissolved TPH-d plume and monitoring well MW-3 lies near the western p margin of the lume. g 1 The horthem, and eastern margins of the. dissolved phase plume have not been fully delineated. Advanced GeoEnvi ran mental,Inc.