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CLEARWATER G R O U ro P, I N C I The TPHg and benzene concentrations in the water sample collected from RW-1 at the end of the constant discharge test were 220 ppb and 12 ppb respectively Predictably, TPHg and BTEX concentrations in water from RW-1 while pumping are significantly less, approximately two orders of magnitude, than those detected during quarterly monitoring events when a relatively small volume of water is purged prior to sampling Water sample results are presented in Table 2 A copy of the certified analytical report and chain-of-custody form is included in Appendix B 5 3 2 Dual-Phase Groundwater and Soil Vapor Extraction Tet Results On December 20, 1995, a dual-phase groundwater and soil vapor extraction test was conducted on RW-1 During the test, pumping rates from well RW-1 were adjusted so that approximately 4 to 5 feet of drawdown were maintained, which created approximately 11 to 12 feet of exposed screen The maximum applied vacuum was 60-inches water column (in w c ), which created an air flowrate of 45 cubic feet per minute (cfm) Vacuums and corresponding flowrates for RW-1 are summarized on Table 4 At this vacuum, it was necessary to pump water from RW-1 at a rate of 7 gpm to keep 11 feet of screen exposed Oxygen concentrations in the extracted vapors were approximately 6%, and the percent of lower-explosive-limit was approximately 55% The effective radius of influence for the vapor extraction well can be estimated using induced vacuum data from observation wells with known distances from the extraction well Vacuums were detected at all observation wells, with a vacuum of 0 12 in w c at the furthest outlying observation well (MW-6 located 74 feet from RW-1) To estimate an effective radius of vacuum influence, a straight line is fitted to the scatter plot between observed induced vacuum versus the logarithm of distance from the extraction well The effective radius of influence is assumed to be equal to the distance from the extraction well where observed vacuums are 1% of the applied vacuum (Johnson and Ettinger, 1994) Using this assumption, the effective radius is then read from the plot where the induced vacuum at the observation wells was equal to 1% of that at the extraction well The effective radius of vacuum influence from RW-1 is estimated to be approximately 35 feet It is important to note that it is only possible to achieve this radius of influence in RW-1 by concurrent groundwater extraction to lower the water table Radius of influence data is presented in Appendix E Based on the flow rates, vacuums, well screens, and radius of influence, the soil air permeability was approximated according to Johnson, et al , (1990) using the software guidance system HyperVentilate c0 The results indicate that the permeability (k) of the vadose zone soil around RW-1 is approximately 5 darcies This value correlates well with that obtained from aquifer test data for the same well Vacuum, flow rate, and permeability data is presented in Appendix E I D-107 PAR RAP / 11 February 21, 1996