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' 18 December 1997 AGE-NC 1 Project No 95-0173 Page 9 of 10 ' • Five quarterly ground water events have been performed from wells MW1 through MW4 However, an overall trend of increasing/decreasing concentrations cannot be established from the analytical data The plots do indicate a trend of increasing depth to ground water in wells MW1 through MW4 since April 1997 (Appendix F) • Since the diesel-range chromatograms for the soil and ground water samples are not ' consistent with typical diesel fuel chromatograms, the detected hydrocarbons are probably of gasoline origin • Results of the dissolved iron and manganese analysis indicated that dissolved iron and ' manganese conditions at the site are adequate for air sparging activity • Field observations and laboratory data indicate that petroleum hydrocarbon-impacted soil ' was encountered from AW 1 at depths between 25 and 75 feet bsg and from AW2 at depths between 35 and 85 feet bsg • Significant dissolved petroleum hydrocarbons were detected from AW1 at a screened interval of 50 to 60 feet bsg, and from AW2 at a screened interval of 60 to 70 feet bsg 1� 5,4. RECOMMENDATIONS ' Based upon data collected during October and November 1997, AGE recommends the following ' • In order to assess the full extent of off-site dissolved petroleum hydrocarbons, a work plan addendum should be submitted for additional ground water monitoring wells south of MW- 9, northwest of MW-6 and east of soil boring 139 (near the intersection of Bonnie Lane and ' Castle Street) • Based on the probable gasoline origin of hydrocarbons, the requirement for TPH-d analysis should be waived and discontinued from future sampling events ' The next quarterly ground water monitoring and sampling event at the site should be scheduled for January 1998 • Although the site is currently being utilised for a Christmas tree lot during the month of December 1997, preparations should be made for an in-situ air sparging pilot test to be I performed in January 1998 Results of the pilot test will be included in a site Corrective Action Plan shortly thereafter ' Advanced GeoEnveronmental,Inc