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CAMBRIA The effective radius of influence is typically defined as an observed vacuum that is greater than or equal to I% of that applied to the extraction well An induced vacuum greater than or equal to I of the applied vacuum was observed in VEW-2 and VEW-1 Induced vacuum observed in well MW-5 was less than I% of the applied vacuum Table 4 presents the vacuum radius of influence data and the effective radius of influence calculation The theoretical radius of influence is estimated according to the steady-state radial distribution equation in A Practical Approach to the Design, Operation, and Monitoring of In Situ Soil Venting Systems (P C Johnson, C C Stanley, M W Kemblowski, D L Byers, and J D Colthart, Groundwater Morutoring and Review, Spring 1990) Based on the test data, a theoretical radius of influence of approximately 35 feet is estimated This estimate likely reflects the vacuum influence within the former UST backfill and not within native soils beneath the site CONCLUSIONS DPE data from wells VEW-1 and VEW-2 suggest DPE is an effective interim remedial technology A lugh vapor flow rate was obtained from well VEW-1 at an intermediate applied vacuum A • moderate vapor flow rate was obtained from well VEW-2 at a lower applied vacuum. The difference in vapor flow rates between the two extraction points is an effect of simultaneous groundwater extraction from well VEW-2 and the different well screen intervals Similar to the vacuum radius of influence data, the vacuum and flow data from these wells may be reflective o� soils within the former UST backfill and not native soils TPHg and MTBE vapor concentrations were relatively low and did not change significantly during DPE from well VEW-1, and TPHg vapor concentrations decreased 37% during DPE from well VEW-2 Benzene concentrations did not change significantly during DPE from VEW-2 Cambria estimates that approximately 35 pounds of TPHg were removed from VEW-1 and 165 pounds of TPHg were removed from VEW-2 during the course of the DPE event Hydrocarbon concentrations in groundwater fluctuated during the DPE in well VEW-2, but were within the h-Lstoricai ranges Following the DPE creat, hydrocarbon concentrations in groundwater from the third quarter 2004 monitoring event also remained within their historical ranges Based on operating data vapor sample analytical results, the total vapor-phase TPHg, benzene, and MTBE mass removed from VEW-2 is estimated at 165 13, 2 28, and 0 03 pounds, respectively (Table 2) The total vapor-phase TPHg, benzene and MTBE mss removed trom VIEW-1 is estimated at 35 21, 0 03, and 0 06 pounds, respectively (Table 2) 0854 9