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. 11 April 2003 <br /> AGE-NC Project No 01-0865 <br /> Page 8 of 9 <br /> • The soil samples collected from bonngs B-11, B-12 and B-13 were all impacted by <br /> petroleum hydrocarbons The highest concentrations of TPH-g (2,200 mg/kg) and TPH-d <br /> (3,500 mg/kg) were detected in sample B11-22 BTEX compounds were detected at <br /> maximum concentrations of 5 4 mg/kg benzene (B11-23), 86 mg/kg toluene (B12-20), <br /> 38 mg/kg ethylbenzene (B11-22) and 131 mg/kg total xylenes (B12-20) In addition, a <br /> soluble form of the gasoline additive MTBE was detected at a maximum concentration of <br /> 99 µg/1 utilizing EPA extraction Method 1311 (TCLP) <br /> • First-encountered ground water in bonngs B 11, B 12 and B 13 was impacted by TPH-g at <br /> concentrations in excess of 5,000 µg/1 In addition, the ground water was impacted by high <br /> concentrations of BTEX compounds,benzene and toluene concentrations were in excess of <br /> the DHS's Maximum Contamination Levels in drinking water However, fuel additives, <br /> including MTBE, were not detected <br /> • The vertical and lateral extent of petroleum hydrocarbon--impacted soil is defined, although <br /> the source of the high petroleum hydrocarbon-impacted soil at the monitoring well MW-6 <br /> location is uncertain The source maybe the former USTs,the ASTs,or a major surface spill <br /> during fuel transfer, however, the only documented subsurface fuel release was from the <br /> former USTs <br /> • The western and eastern lateral extent of petroleum hydrocarbon-impacted ground water is <br /> defined, the northern and southern lateral extent, and the vertical extent are not defined <br /> e The information available to date does not preclude the former USTs as the source for <br /> contaminated soil and ground water at the site The dissolved contaminant distribution <br /> encountered at the Herman & Helen's Marina site can be interpreted to represent a plume <br /> originating from the former UST area <br /> 6.0. RECOMMENDATIONS <br /> Based upon the findings of this investigation, AGE recommends <br /> • Performance of additional assessment to determine the source of high concentrations of <br /> petroleum hydrocarbon-impacted soil and ground water at the monitoring well MW-6 <br /> location <br /> • Performance of additional assessment to delineate the vertical extent and the northern and <br /> southern lateral extent of petroleum hydrocarbon-impacted ground water <br /> • <br /> Advanced GeoEn"ronmental,Inc <br />