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29 January 1996 <br /> AGE-NC Project No 95-0143 <br /> Page 5 of 6 <br /> 4 3 RELATIVE GROUND WATER ELEVATION AND GRADIENT <br /> The relative elevation of ground water in each well was calculated by subtracting the depth to water <br /> from the surveyed casing elevation (Table 1) Ground water rose an average of 1 08 feet between <br /> May and October 1995 and dropped an average of 0 38 feet between October and November 1995 <br /> The approximate gradient was calculated to be 0 0016 ft/ft and 0 0014 ft/ft directed north to <br /> inorthwest for the October and November 1995 sampling events, respectively Relative ground water q� i <br /> elevation contours for the October and November 1995 monitoring events are illustrated as Figures lV <br /> i3 and 4, respectively <br /> i44 ANALYTICAL.RESULTS OF WATER SAMPLES <br /> TPH-g was detected in samples from MW-6, MW-7 and MW-9 at concentrations of 2,400 J.cg/l <br />' (micrograms per liter, equivalent to parts per billion ppb), 20,000 ppb and 87,000 ppb, respectively <br /> BTE&X were detected in the same wells at concentrations up to 18,000 ppb (xylenes, MW-9) Free <br /> product was encountered in MW-3,therefore, no sample was collected Toluene and xylene were also <br /> detected in MW-10 at concentrations of 0 87 ppb and 0 80 ppb, respectively No petroleum <br /> hydrocarbons were detected in samples from MW-14, MW-15, MW-16 or MW-17 Analytical <br /> results are summarized on Table 3 The laboratory reports (MAI Laboratory I D Nos 57225 - <br /> i57228 and 58877 - 58880) and chain-of-custody forms are included in Appendix C <br /> i5.0. CONCLUSIONS & RECOMMENDATIONS <br /> i5 1 HYDROCARBON-INIPACTED SOIL <br /> Based upon analytical results from the current and past investigations at the site, hydrocarbon- <br /> impacted soil within the vadose zone appears to be limited to the immediate vicinity of the former <br /> UST area However, low concentrations of hydrocarbons are present within the capillary fringe and <br /> lower vadose zone approximately 60 feet north and 20 feet south of the former UST area <br /> se7 Since impacted soil at the site has a relatively limited concentration and extent, we do not recommend <br /> active soil remediation at this time <br /> I <br /> 5 2 HYDROCARBON-IMPACTED GROUND WATER <br /> i. <br /> On1y low co Y concentrations of toluene and xylenes were detected in MW-10 and no petroleum <br /> hydrocarbons were detected in wells MW-14, MW_15, MW-16 and MW-17, defining the extent of <br /> i <br /> i <br />