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I 1 4 2 Vapor Test Well Construction and Vapor Extraction Test ' In October 1995, Ground Zero deepened soil borings SB-25 and SB-26 from approximately 40 to 60 feet bgs, soil borings SB-24 and SB-29 were deepened from 55 to 60 feet bgs These borings were then widened with 12" diameter augers to allow construction of vapor extraction test wells in the borings 4-inch diameter vapor test well VW-1 and 2-inch diameter vapor test well VW-2 were constructed in soil boring SB-29 in order to allow for I ' separate vapor extraction of higher permeability and lower permeability sediments, respectively, from the same soil boring 4-inch diameter vapor test well VW-4 and 2-inch ` diameter vapor test well VW-5 were constructed in soil boring SB-26 for the same reason Four-inch vapor test wells VW-3 and VW-6 were constructed in borings SB-24 and S13-25, respectively Soil boring SB-37 was deepened from approximately 55 to 75 feet bgs and momtormg/ambient air well MW-13 was constructed in the boring Construction details for the vapor test wells and the ambient air/monitoring well are summarized in Table i f Ground Zero performed a vapor extraction test at the subject site on October 12 and 13, 1995, to evaluate the use of vapor extraction as a method for remediating vadose soil Field results indicated air flow rates ranging from 31 to 53 cubic feet per minute could be extracted from wells VW-1 through VW-6 at an applied vacuum ranging from 14 to 45 inches water column Air samples contained TPHg concentrations ranging from 11,000 to 29,000 mg/m3 and benzene concentrations ranging from 300 to 1,600 mg/m3 The observed radii of influence averaged approximately 30 feet (Figure 3) Based upon test data Ground Zero concluded that vapor extraction is a feasible technology to remove gasoline 4W hydrocarbons from beneath the site The vapor extraction test report in included in Appendix 6 1.4.3 Fourth Quarter 1995 Monitoring and Sampling e ' In November 1995, Ground Zero developed ambient air/monitoring well MW-13, monitored 1 depth to water in wells MW-1 through MW-13, sampled wells MW-4 through MW-13, and surveyed well head elevations for wells MW-8, and MW-13 Several inches of water had collected in the endcaps of wells MWA through MW-3, however sufficient groundwater was not present to sample the wells Gasoline hydrocarbons were detected in groundwater from 3 all wells sampled Groundwater was not present in wells MW-1 through MW-3 The report for this monitoring and sampling event is included as Appendix 7 Groundwater elevation data and analytical results for groundwater samples collected by Ground Zero are also summarized in Tables 3 and 4, respectively 1 On November 11, 1995 Ground Zero measured depths to groundwater in monitoring wells MW-1 through MW-13 to evaluate the elevation of the groundwater surface in each well and the groundwater gradient across the site A map of the potentiometric surface at the site is presented in Figure 4 Data used to compile the potentiometric surface map are presented in Table 3 along with previous water level data obtained by Ground Zero Groundwater elevation data collected by previous consultants is presented in the tables prepared by Mill groundzelroeklcap 3