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_ f 15 February 2000 AGE-NC Project No. 98-0448 Page 11 of 33 I operation The greatest concentration of OV was detected in MW-4A and EW-1 The OV concentration at MW-4A went from 92 ppm (initial reading) to 1,074 ppm after 7'/z hours of IAS operation, the OV concentration at EW-1 went from 40 ppm to 1,134 ppm after 2 hours The ' increase in OV may mdicate stripping and volatilization of hydrocarbons from the saturated zone in response to the IAS pilot test OV measurements are summarized in Tables 3, 4, 5, 6 and 7 ' 4 2 4 Ground Water Depth Significant increases in ground water elevation during the IA.S pilot test is indicative of ground water mounding, no significant ground water elevation changes were observed in wells MW-1, MW-2, MW-4A, EW-1 and MW-6 The tendency for ground water mounding during performance of IAS ' can cause the dissolved hydrocarbon plume to migrate beyond its original horizontal extent Depth to ground water measurements are summarized in Tables 3, 4, 5, 6 and 7 1 4 2 5 Laboratory Results of Ground Water Sample A laboratory analysis of a ground water sample collected from EW-1 reported dissolved iron and manganese at concentrations of 0 20 parts per million(ppm,reported as milligrams per liter) and 6 8 ' ppm, respectively The laboratory report (MAI Lab I D Number 24715) and chain-of-custody form ' are presented in Appendix H Based on the guide How to Evaluate Alternative Cleanup Technologies i For UST Sates (October 1994) published by the United States Environmental Protection Agency (EPA) Office of USTs, the presence of dissolved iron/manganese (Fe"/Mn") in ground water can reduce the permeability of the saturated zone soils during air sparging operations The guide further states in Exhibit VII-12 Dissolved Iron And Air Sparging Effectiveness that concentrations of ' dissolved iron/manganese less than 10 mg/1 are acceptable concentrations for air sparging, concentrations between 10 mg/1 and 20 mg/l would require periodic testing or periodic replacement, if concentrations were greater than 20 mg/l,then air sparging was not recommended Results of the ' laboratory analysis indicated that dissolved iron and manganese conditions at the site are suitable for air-sparging activity 1 5 0. GROUND WATER DRAW-DOWN PILOT TEST ' On 14 July 1999, an8-hour ground water draw-down pilot test (pump test) was performed at the site to evaluate feasibility of ground water "pump and treat" as a remedial alternative and to evaluate ' aquifer characteristics such as hydraulic conductivity, transmissivity and ground water draw-down at various pumping rates Advanced GeoEnvironmental,Inc I