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-, r <br /> • 26 January 2003 <br /> AGE-NC Project No 98-0521 <br /> I <br /> ' Page 3 of 4 - <br /> r ' <br /> • BTEX compounds were detected only in the sample collected from monitoring well MW-4 <br /> at concentrations of 70µg/1 benzene,2 8 µg11 toluene, 19µg11 ethylbenzene and 24 µg11 total , <br /> xylenes <br /> fll ' W <br /> MTBE'was detected in wells MW-1, MW-2 and MW-4 by EPA Method 8260B at <br /> concentrations of 7 0 µg/1, 190 µg/1 and 150 µg/1, respectively <br /> • <br /> No'other fuel oxygenates were detected in the samples collected during the December 2002 <br /> ' monitoring event <br /> 1 Analytical results from the monitoring well ground water samples are summarized in Tables 2 and 3 <br /> The laboratory report (MAI Lab IDs 0212211-001 through 0212211-004),QA/QC and chain-of- <br /> custody are Included In Appendix C <br /> I � A <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 8 4 feet bsg The prevailing <br /> r ground water flow direction at the site has been generally toward'the northeast for nine <br /> monitoring events The ground water hydraulic gradient was estimated to be 0 011 foot/footI <br /> ' nl ' <br /> • Dissolved phase hydrocarbon's, 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 /> II „'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 µg/1 in drinking water The concentrations of <br /> MTBE detected in samples MW-1, MW-2 and MW-4 were,above the,DHS's Secondary I <br /> lMCL of 5 µg11 in drinking water ' <br /> I I ' r 1 4 I <br /> ! The approximate lateral extent of impacted soil and ground water has been defined by the <br /> installation of soli borings and the current monitoring well network The vertical extent of <br /> ' dissolved hydrocarbons in the former UST area may require additional assessment <br /> I , <br /> ni Q 1 01 4 a <br /> Advanced GeAnvironmental,Inc' <br /> L <br /> t I C iklo I d ! p { j l J � <br />