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28 February 1997 <br /> AGE-NC Project No 96-0I73 <br />' Page 3 of 4 <br /> 32 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br /> During the December 1996 sampling, TPH-g was detected in samples collected from MW-I through <br /> MW-4 at concentrations as high as 120,000 parts per billion (ppb, reported as micrograms per liter), <br /> TPH-d was detected in samples collected from MW-1 through MW-4 at concentrations as high as <br /> 33,000 ppb, however, the laboratory report indicated that detection of TPH-d was the result of <br />' gasoline interference <br /> BTEX were detected in ground water samples collected from well MW-1 through MW-4 Benzene <br />' was detected in MW-1 through MW-4 at concentrations as high as 14,000 ppb, toluene was detected <br /> in MW-1 through MW-4 at concentrations as high as 8,400 ppb, ethylbenzene was detected in MW-1 <br /> through MW-4 at concentrations up to 3,400 ppb, xylenes were detected in MW-1 through MW-4 <br />' at concentrations as high as 16,000 ppb Analytical results of TPH-g and BTE&X in ground water <br /> are summarized in Table 2 - Analytical Results of Giound Water Samples The Iaboratory report <br /> (CAL Reference Number 956) and chain-of-custody forms are presented in Appendix B <br /> MTBE was not detected from any ground water monitoringwells at the site for the second straight <br /> g <br /> quarterly ground water monitoring event <br /> 4 0. CONCLUSIONS AND RECOMMENDATIONS <br /> 41 CONCLUSIONS <br /> IBased on the results of ground water monitoring in December 1996, AGE has concluded the <br /> following <br /> • Ground water flow direction continues to remain relatively constant at the site, with ground <br /> water flowing toward the northeast Ground water monitoring wells MW-3 and MW-4 are <br /> Ilocated down-gradient of the former UST area <br /> Laboratory analysis of groundwater samples indicated that from August to December 1996, <br /> total petroleum hydrocarbons quantified as gasoline increased in MW-1, MW-2 and MW-3 <br /> by 31, 41 anu 20 perce t, respectively, While decreasing in M`vV-4 by 4 percent <br /> • Concentrations of benzene, toluene, ethylbenzene and xylenes detected in MW-1 through <br /> MW-4 were above the State of California Maximum Contaminant Levels(MCLs) for drinking <br /> water of 1 0 ppb, 150 ppb, 700 ppb and 1750 ppb, respectively <br /> • The greatest concentrations of dissolved petroleum hydrocarbons continues to be in the area <br />. of well MW-3, down-gradient of the former UST area <br /> The ground water data collected over the past two quarters suggests that MTBE is not <br /> I <br />