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' 3 <br /> • 0 September 1999 <br /> AGE-NC Project No 97-0351 <br /> Page 3 of 4 <br /> ' 3 2 HYDROCARBON-IMPACTED GROUND WATER <br /> The results of laboratory analysis of ground water samples collected at the site over the last quarter <br /> ' are as follows <br /> • TPH-g was detected in the sample from ground water monitoring wells MW-1,MW-3, MW- <br /> ' 4 and MW-5 at concentrations of 3,700 micrograms per liter (4g11), 110 ug/l, 170 ug/l and <br /> 120 µg11, respectively <br /> ' • BTEX compounds were also detected in the sample from monitoring well MW-1 as great as <br /> 240 ug/l (benzene well MW-1) Relatively low concentrations of BTEX compounds were <br /> detected in the samples collected from well MW-3, MW-4 and MW-5 <br /> t • TPH-d was detected in the samples from ground water monitoring wells MW-1 and MW-2 <br /> at concentrations of 1,600 µg/l and 72 ug1l, respectively TPH-d µas not detected in the <br /> other ground water samples analyzed <br /> • The low concentrations of various BTEX compounds detected in ground water samples <br /> ' • collected from monitoring wells MW-3, MW-4 MW-5 may be the result of cross <br /> contamination of the samples,possible due to purging the wells with a new type of hose that <br /> resisted decontamination procedures The affected wells have had no or little detectable <br /> ' concentrations of the analytes during the previous three ground water monitoring events, and <br /> each newly detected analyte has similar concentrations in the three wells AGE anticipates <br /> that the analytical results from samples collected from the monitoring wells during the next <br /> ' monitoring event will be similar to the results for the first set of monitoring events <br /> • MTBE and ETBE were detected in the water sample from well MW-4 by EPA Method <br /> ' 8260M at concentrations of 6 4 ug/l and 2 7,ug/l, respectively MTBE was also detected in <br /> the water sample collected from well MW-2 at a concentration of 16 ug/l <br /> ' Laboratory results of samples analyzed for petroleum hydrocarbons are summarized in Table 2 and <br /> Table 3 The laboratory reports (MAI Laboratory ID 16618 through 16622 and 16681), quality <br /> ' assurance and quality control (QA/QC) reports and chain-of-custody form is included in Appendix <br /> B <br /> ' 4.0. SUMMARY AND CONCLUSIONS <br /> ' Based upon the results of this quarterly monitoring event, AGE concludes <br /> • The greatest concentrations of dissolved petroleum hydrocarbons were detected in samples <br /> ' collected from well MW-1, near the former western UST location While for the first time <br /> Ad%anced GeoEn.ironmentaI,Inc <br />