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1 <br /> . 6 July 2003 <br /> AGE-NC Project No 98-0521 <br /> Page 3 of 4 <br /> ' • TPH-g was detected in the sample collected from monitoring well MW-4 at a concentration <br /> of 3,400 micrograms per liter(µg/1), TPH-g was not detected in the samples collected from <br /> monitoring wellg MW-1, MW-2 and MW-3 <br /> • BTEX compounds were detected only in the sample collected from monitoring well MW-4 <br /> at concentrations of 390 µg/1 benzene, 18 µg/1 toluene, 150 gg/l ethylbenzene and 260 pLg/l <br /> total xylenes <br /> ' • MTBE was detected in wells MW-1 MW-2 and MW-4 by EPA Method 8260B at <br /> ' concentrations of 2 7 gg/l, 250 µg/1 and 520 gg/l, respectively <br /> — • No other fuel oxygenates were detected in the "samples collected during the March 2003 <br /> monitoring event <br /> Analytical results from the monitoring well ground water samples are summarized in Tables 2 and 3 <br /> ' The laboratory report (MAI Lab IDs 0303424-001 through 0303424-004),QA/QC and chain-of- <br /> custody are included in Appendix C The lateral extent of dissolved contaminants is depicted on <br /> Figure 4 <br /> lie <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> The following conclusions were drawn from the results of this investigation <br /> ' Ground water at the site was encountered at approximately 7 7 feet bsg The prevailing <br /> ground water flow direction at the site has been generally toward the northeast for ten <br /> momtonng events The ground water hydraulic gradient was estimated to be 0 012 foot/foot <br /> • Dissolved phase hydrocarbons, including TPH-g, BTEX and MTBE were present in the <br /> - sample from MW-4, located within the former UST area MTBE was also detected in`the <br /> samples collected from MW-1 and MW-2, located cross-gradient and down-gradient, <br /> ' respectively, from the former UST area <br /> • The concentration of benzene detected in the sample MW-4 was above the DHS's Primary <br /> ' Maximum Contaminant Level (MCL) of 10 gg/l in drinking water The concentrations of <br /> MTBE detected in samples MW-2 and MW-4 were above the DHS's Secondary MCL of 5 <br /> µg/1 in drinking water <br /> • The approximate lateral extent of impacted soil and ground water has been defined by the <br /> mstallation of soil borings and the current monitoring well network The vertical extent of <br /> dissolved hydrocarbons in the former UST area may require additional assessment <br /> ' Advanced GeoEnvironmental,Inc <br />