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test was conducted by creating a vacuum in the extraction well with a portable vapor pump. The air flow rate at the well was determined by measuring the flow-induced pressure differential across a pitot tube on the pump, and converting to flow rate using the manufacturer's conversion equation. Vacuum versus time data were collected from the extraction well and the observation wells using Magnehehc' pressure gauges,which record negative pressure (vacuum)in equivalent inches of water. The data were recorded as net pressure drawdown from the initial soil pressure (atmospheric) within the sealed well casing The test was conducted for 3 hours; testing was considered complete when no significant vacuum change was measured in the observation wells over a 15-minute period. The distance between test wells and observation wells vaned from 10 to 30 feet (see Figure 2). Refer to Appendix A for details of vapor test protocol, data acquisition procedures, and test equipment. Periodically during the test, effluent hydrocarbon vapor concentrations were measured with a hydrocarbon detector at the vapor extraction pump with a combustible gas indicator. An analytic-grade effluent sample was collected from the extraction well 30 minutes into the test. The air sample was collected in a 64iter evacuated stainless steel canister. Extraction Well Vacuum and Flow Rates During the test, extraction from MW-10 caused a vacuum of approximately 36 to 40 inches of water (units of pressure) in the well, corresponding to an approximate flow rate of 48.0 cubic feet per minute (cfm) Monitoring well responses were recorded during the test. A maximum vacuum of 1.9 inches of water was detected 22 feet from the extraction well at MW-2 A minimum vacuum of 0 63 inch of water was observed 10 feet away in MW-1. Air Parameter Estimates A time dependent transient analysis was applied to observation well vacuum response. The Hantush fluid-flow model was selected because it provides information regarding air leakage from the ground surface and vertical permeability of the material through which leakage is occurring. This information is important because the effective zone of vapor capture is, in part, determined by the "leakiness" of the soil and site cover. Air transmissivity, storage, and r/B values, components of the Hantush well function for a leaky aquifer predicted from Hantush analysis, are presented in Table 2 below. The r/B parameter is proportional to the radius from the pumping well and the vertical air permeability of the leaking unit; greater r/B values suggest greater air permeability and leakage Vapor extraction test procedures are presented in Appendix A. Additional discussion of the Hantush method is included in Appendix B 3