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Mr Jeff Wong Page 7 of 10 MTBE in groundwater beneath the site in December 2003 and March 2004 are presented on Figures 10 and 11, respectively Vapor Extraction Test Results During the VET using well MW 1 as the extraction well, induced vacuum was observed in each of the observation wells, with immediate influence observed in wells V W 1 and MW2 The flowrate from MW was relatively low,at approximately 10-15 cubic feet per minute (cfin), with an applied vacuum between 18 and 20 inches of water During the vapor extraction test using test well V W 1 as the extraction well, induced vacuums were observed in each of the observation wells The flowrate from VWI ranged from 20 to 24 cfim, with an applied vacuum between 50 and 58 inches of water Vapor concentrations were monitored during the testing of each vapor well with a PID Monitoring was conducted on the influent vapor stream prior to the addition of any dilution air In most cases, the PID could not quantify the influent vapor concentrations as they were high enough to trip the instrument alarm(concentrations greater than 2,000 ppmv) A summary of VET monitoring data is presented in Table 5 Field notes are included in Attachment E Estimated Radius of Influence During the test on MWl (screened from 60 to 80 feet bgs) an induced vacuum of 0 33 to 0 36 inches of water was observed in well VW1 (screened from 55-70 feet bgs) and an induced vacuum of 0 15 to 0 22 inches of water was observed in well MW2 (screened from 58 to 78 feet bgs) During the test on V W 1 the induced vacuum in wells MW 1, MW2, and MW4 ranged from 0 79 to 0 83 inches of water, 0 48 to 0 50 inches of water, and 0 40 to 0 41 inches of water, respectively In Ground Zero's experience at other sites we have found that the common effective radius of influence of a vapor well is approximately 30 feet The minimum radius of influence typically measured in fine-grained soils is 15 to 20 feet Based upon the lithology exhibited in site cross sections (Figures 3 and 4) and the data from the VETS, we expect that subsurface vapor flow near the water table will be primarily within the thin sand unit between the depths of approximately 55 and 60 feet bgs, with a radius of influence of approximately 35-50 feet However, analytical results of soil samples collected at the site suggest that the bulk of residual soil contamination in the vadose zone lies in fine-grained sediments The primary mode of vapor removal within this zone is via diffusion due to the low permeability of the soil zone (silt/clay) Thus the mass loss rate from contaminated soil will be limited by the rate of diffusion of contamination from the less permeable zones to the more permeable sand zones Laboratory Analyses and Results Vapor samples were collected from the vapor stream pnor to the addition of dilution air The samples were collected in Tedlar bags and transported under chain of custody to State-certified Air Toxics, Ltd G IGROUNDZEITULEBURGIReports�HSA_Mud wells Report 2 doc