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20 January 2003 AGE-NC Project No 95-0109 Page 7 of 8 was not detected in the adjacent HU2 well MW-19, screened from 75 feet to 80 feet bsg It is likely that TPH-g-impacted ground water does not extend much deeper than 117 feet bsg on-site and beyond first encountered ground water off-site • One or more BTEX compounds were detected in samples from the same wells at concentrations as high as 38 µg11 benzene and 3 1 µg/1 toluene in MW-14, 25 µg/1 ethylbenzenc in MW-9 and 130 µg/1 total xylenes in well MW-8 Benzene was not detected in samples collected from wells MW-15 through MW-19 • 1,2-DCA was detected in samples collected from HU1 wells MW-1,MW-3,MW-4,MW-5, MW-7,MW-9,MW-11,MW-13,MW-14,MW-16 and EW-1 at concentrations ranging from 0 56 µg/1(MW-13)to 54 µg/1(MW-1)and HU2 well MW-15 at a concentration of 1 1 µg/1 1,2-DCA was not detected in HU2 well MW-19 and the HU3 wells MW-17 and MW-18,the vertical extent of the 1,2-DCA contamination appears to be defined • TBA was detected in the water samples collected from HUl wells MW-9 and MW-14 at concentrations of 29 µg/1 and 19 µg/1,respectively, the concentrations are above the DHS's Action Level (AL) for TBA in drinking water TBA has been detected sporadically in all HU1 wells except MW-2, MW-3, MW-10, MW-13 and MW-16 • Eight additional VOCs were detected by EPA Method 8260B, in HU1 samples MW-5, MW-8 and MW-9, all concentrations were below their respective DHS' Action Levels • Over the past four quarters TPH-g,BTEX and 1,2-DCA concentrations in groundwater have remained relatively stable in all the wells with a few exceptions Concentrations of TPH-g, BTEX and 1,2-DCA have increased slightly in well MW-1, 1,2-DCA has decreased in well MW-3 and TPH-g and benzene have decreased to non-detectable levels in well MW-5 1,2-DCA was detected at low concentrations this quarter in wells MW-1I and MW-13, which is the first detection of 1,2-DCA in well MW-11 since March 1998 and is the first detection ever in well MW-13 since 1-2-DCA analysis began in March 1998 • The extent of petroleum hydrocarbon-impacted ground water appears to be contained within the current on- and off-site well network The southern lateral extent of 1,2-DCA-impacted ground water is not defined 5.0. RECOMMENDATIONS Based upon data collected from the site, AGE recommends • Continued quarterly groundwater monitoring as required by Clean-up and Abatement Order No 93-701 The next groundwater monitoring event will be scheduled for March 2003 Advanced GeoEnvironlnental,Inc