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, f y „ FIS � Y ' 01 November 2005 AGE-NC Project No 95-0142 ' Page 8 of 8 - - } 1 ground-water flow pattern may be influenced by a difference in hydraulic heads from wells ' screened at two different depth intervals (between 25 feet and 60 feet bsg, and between 70 feet and 80 feet bsg) Compared to the fine-grained soils between 25 and 60 feet bsg, the Interval between 70 and 80 feet bsg appeared more sand-prone, and may be associated with ' a different hydrogeologic unit • During the second and third quarters of 2005, TPH-g was not detected in the samples ' collected from the wells, BTEX compounds were detected only once • During the second quarter 2005,the fuel additive MTBE was detected in one monitormg well (MW-7),however, all monitoring wells are"drowned"and analytical data from these wells ' may not be representative of shallow ground water conditions • Historically,the highest concentrations of dissolved petroleum hydrocarbons were detected ' in shallow well VW-1, located in the area of former UST TK1-90, however, TPH-g and BTEX concentrations in the deep-screened well (MW-6) at TK 1-90 have.steadily declined to non-detectable levels ' MTBE has been detected in ground water samples collected from well MW-7 for eight - consecutive monitoring events,and sporadically from well MW-5,the distribution of MTBE suggests that the MTBE plume has migrated laterally and vertically from the former UST location to wells MW-5 and MW-7 r5.0. RECOMMENDATIONS ' Based upon the results of the remediation activities to date, AGE recommends • Continuation of ground water remediation with a possible addition of extraction vapor wells ' VW-2 and VW-4,and discontinue soil-vapor extraction due to non-detect levels of extracted hydrocarbons • Continuation of the quarterly ground water monitoring program - 6.0. LIMITATIONS Our professional services were performed using that degree of care and skill ordinarily exercised by environmental consultants practicing inthisor similar localities The findings were based upon ' analytical results provided by an independent laboratory Evaluations of the hydrogeologic conditions at the site for the purpose of this investigation were made from a limited number of data ' points (i a soil-vapor and ground water samples) and subsurface conditions may vary away from these data points No other warranty, expressed or implied, is made as to the professional interpretations, opinions, recommendations contained in this report ' Advanced GcoEnvironmental,Inc 1