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20 July I998 <br /> AGE-NC Project No 95-0137 <br /> ' Page 7 of 8 <br /> ' 4.0. CONCLUSIONS AND RECOMMENDATIONS <br /> 41 CONCLUSIONS <br /> ' Based upon data collected during the January 1997 monitoring event, AGE concludes <br /> • The highest concentration of gasoline related dissolved hydrocarbons continues to be in the <br /> area of monitoring well MW-2 and soil vapor wells VW-1 and VW-2, surrounding the <br /> former UST area, located near the northern edge of the site TPH-g concentrations detected <br /> ' in well MW-2 to date have been at a maximum of 14,000 ppb Current TPH-g concentrations <br /> are approximately one-half of the maximum contaminant concentrations detected at the site <br /> ' Detectable concentrations of TPH-g decreased in a majority of the wells over the last quarter <br /> TPH-g was detected at low concentrations in the wells established on the Jimco site The area <br /> of the significant dissolved TPH-g, concentrations above 350 ppb, is limited to the former <br /> UST area <br /> • Over the last quarter, TPH-d concentrations increased only well MW-3 The highest <br /> '• concentrations of TPH-d was in the samples collected from monitoring well MW-2 and soil <br /> vapor well V W-1 Hydrocarbon-impacted groundwater extends north and northeast of the <br /> former RFS UST area onto the Jimco Truck Stop property The lateral extent of the dissolved <br /> ' TPH-d,plume over 1,000 ppb has been defined within the current well configuration <br /> • Benzene concentrations detected in well MW-2 to date have been at a maximum of 1,400 <br /> ' ppb and a minimum of 220 ppm, while the current concentration is 850 ppb Benzene <br /> concentrations overall decreased in wells The highest detected dissolved benzene <br /> concentration was in the sample from upper well screen of well VW-1, located directly west <br /> ' of the former UST area <br /> • The areal distribution of substantial concentrations of dissolved BTE&X compounds was <br /> ' limited to the former UST area No BTE&X compounds were detected in wells MW-4 or <br /> MW-5 While wells MW-6,MW-7 and MW-8 contained only low concentrations of xylene <br /> • The oxygenated compounds DIPE and TBA were detected on the site The concentrations <br /> of TBA were similar to the previous sampling event and DIPS was only detected on the <br /> Jimco site <br /> ' Advanced GeoEnvironmental Int <br />