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31 July 1996 <br /> • AGE-NC Project No 95-0105 <br /> ' Page 4 of 6 <br /> relative to a City of Tracy bench mark in 1988 <br /> The relative ground water elevations ranged from, 3 97 feet in MW-5 to 7 10 feet in MW-6 Ground <br /> water elevation increased an average of 0 3 feet at the site between January and May 1996 The <br /> ground water gradient appears to follow the regional and historic gradient to the north <br /> 3 3 FIELD AND LABORATORY RESULTS OF SOIL 0 SAMPLES <br /> Organic vapors were detected in soil samples collected from boring MW-4 at concentrations up to <br /> 968 parts per million (ppm) Organic vapors were not detected in duplicate soil samples collected <br /> from borings MW-4 or MW-5 <br /> TPH-d was detected in samples from MW-4 at concentrations up to 11 ppm (8-foot depth) TPH-g <br /> ' and BTE&X were detected only in samples from MW-4 at concentrations up to 32 ppm <br /> Hydrocarbons were not detected in soil samples analyzed from MW-5 or MW-6 The analytical <br /> results of the soil samples are depicted in Table 2 - Analytical Results of Soil Samples The <br /> laboratory report (MAI Laboratory Nos 65049 to 65054) and chain-of=custody are included in <br /> Appendix D <br /> 3 4 PETROLEUM HYDROCARBON-IMPACTED GROUND WATER <br /> ' TPH-g and TPH-d were detected in MW-4 at concentrations of 43,000 and 5,700 parts per billion <br /> (ppb, reported as micrograms per liter kig/l), respectively Benzene, toluene, ethyl benzene and <br /> ' xylenes were detected in MW-4 at concentrations of 320 ppb, 3,600 ppb, 1,900 and 8,300 ppb, <br /> respectively Benzene was also detected in the sample from MW-3 at a concentration of 2 2,ppb <br /> ' Petroleum hydrocarbons were not detected in wells MW-1, MW-2, MW-5 or MW-6 However, the <br /> detection limit for MTBE in MW-4 was raised to 130,ug/l due to matrix interference The analytical <br /> results for the ground water samples are summarized in Table 3 The laboratory report (MAI <br /> ' Laboratory Nos 65265 to 65270) and chain-of custody are included in Appendix E <br /> 4.0. CONCLUSIONS AND RECOMMENDATIONS <br /> 41 HYDROCARBON-IMPACTED SOIL <br /> 1• `Based upon analytical results for soil samples collected at the site, hydrocarbon-impacted soil <br /> extends north and west of the former UST area, off-site under Grant Line Road However, <br /> 1 <br />