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i e s t �. 21 April 2000 AGE-NC Project No 95-0144 Page 3of5 r ' 3 1 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 November 1999 and February 2000, ground water elevation increased 1 03 feet in monitoring well MW-21B, screened below a clay layer Ground water elevation increased between 0 42 and 0 55 feet in the remaining wells The approximate hydraulic gradient for the February 2000 monitoring event was calculated to be 0 0028 ft/ft with a northerly flow direction Ground water elevation contours derived from data collected on 07 February 2000 are depicted in Figure 3. Ground water was between approximately 0 47 and 5 83 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 Groundwater was within the screened intervals of MW-19A, MW- 20A and MW-21A Ground water elevations in wells MW-19, MW-20 and MW-21 were between 1 19 and 1 84 feet lower in the lower screened intervals beneath the confining clay layer than in the upper screened interval Data from the upper screened interval, established in first-encountered ground water was lie used for,gradient determination 32 ANALYTICAL RESULTS OF WATER SAMPLES , During the February 2000 monitoring, TPH-g was detected in samples from monitoring wells MW- 21A and MW-21B at concentrations of 3,800 parts per billion(ppb,reported as micrograms per liter) 'r and 800 ppb, respectively BTEX compounds were detected in samples from wells MW-1, MW- 21A and MW-21B at concentrations as high as 1,500 ppb (benzene,MW-2l A) TPH-d ryas detected in wells MW-19A, MW-20A, MW-21A, MW-19B, MW-20B and MW-21B at concentrations ranging from 53 ppb to 3,100 ppb TPH-mo was detected 3n monitoring wells MW-21 A and MW- 21B at concentrations of 810 ppb and 330 ppb, respectively The shift in hydrocarbons from MW-21 to MW-20, observed in the November 1999 sampling event reverted back to the previous patter during the February 2040 monitoring event Hydrocarbon concentrations in the remaining wells generally remained low or non-detect MTBE was detected in ground water samples from well MW-21 B at a concentration of b 0 ppb Other oxygenates were not'analytes for the samples collected at the site during the February 2000 monitoring event Histoncally, only low concentrations of MTBE and TBA have been detected intermittently at the site Analytical results for February 2000 are summarized on Table 2 Analytical results of historical ground water samples are summarized on Table 3 The laboratory report (MAI Laboratory I D Nos 30794-30808) and chain-of-custody forms are included in Appendix C Advanced GeoEnraronmental,i[sc u