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28 January 1996 <br /> ' AGE-NC Project No 95-0144 <br /> Page 5 of 6 <br /> ' custody forms are included in Appendix C <br /> ' 4 3 RELATIVE GROUND WATER ELEVATION AND GRADIENT Y <br /> ' The relative elevation of ground water to each well was calculated by subtracting the depth to water <br /> from the surveyed casing elevation (Table 1) Ground water rose an average of 0 96 feet between <br /> May and October 1995 and dropped an average of 0 60 feet between October and November 1995 <br /> ' The approximate gradient was calculated to be 0 0053 ft/ft with a northerly direction for both <br /> sampling events Ground water elevation contours derived from data collected on 5 October and 20 <br /> November 1995 are depicted in Figures 3 and 4 <br /> 44 ANALYTICAL RESULTS OF WATER SAMPLES <br /> 1 TPH-g and TPH-d were detected in MW-1 and MW-12 at concentrations as high as 280 ppb <br /> Benzene and ethyl benzene were detected in MW-1 at concentrations of 6 3 and 13 ppb, respectively, <br /> Mtoluene was detected in wells MW-1, MW-11 and MW-12 at concentrations as high as 18 ppb, and <br /> xylenes were detected in wells MW-1 and MW-5 at concentrations of 70 and 1 8 ppb, respectively <br /> No petroleum hydrocarbons were detected in samples collected from MW-2, MW-4, NiW-S, TNIW-13 <br /> ' or MW-18 Analytical results are summarized on Table 3 and 4 The laboratory report (1vIAI, ID <br /> #57229 - 57236, 58874) and chain-of-custody forms are included in Appendix C <br /> 5.0. CONCLUSIONS & RECONENIENDATIONS <br /> ' No petroleum hydrocarbons were detected in wells MW-8, NIW-13 and NRNI-18 and only low <br /> concentrations of hydrocarbons were detected m wells MW-I 1 and MW-12 Based upon these data, <br /> ' the dissolved hydrocarbon plume does not appear to extend off-site to the north or east <br /> The highest concentrations of hydrocarbons continue to be detected in MW-1, near the former UST <br /> ' excavation The dissolved hydrocarbon plume may extend as much as 60 feet north of MW-1 <br /> Overall, the concentrations of hydrocarbons in ground water on the site (including MW-1) have <br /> decreased between December 1994 and November 1995 <br /> ' An air sparging pilot test is scheduled to be performed at the site at the beginning of February 1996 <br /> Data obtained during the pilot test will be used to prepare a Corrective Action Plan (CAP) to <br /> ' determine remedial options for the site Additionally, the next quarterly monitoring should be <br /> scheduled for February 1996 <br />� 1 , <br /> 1 <br />