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15 February 2000 <br /> AGE-NC Project No 98-0448 <br /> hPage 17 of 33 <br /> 8 12 Required Soil Conditions <br /> The blower in a vapor extraction system creates an induced vacuum in the subsurface, generating <br />' vapor flow towards the area of lowered air pressure (the extraction point) through the soil pore <br /> spaces The efficiency of this process is proportional to soil porosity and intrinsic permeability <br /> Intrinsic permeability is the measure of the ability of soils to transmit fluids, porosity is the <br />' percentage of soil that is void of material A high moisture content in soils can reduce the <br /> effectiveness of SVE by restricting the flow of air through soil pores Generally,coarser grained soils <br /> (i e , sands) are the desired material for a SVE technology because coarser grained soils have a <br /> greater intrinsic permeability than finer grained soils (i e , clays) <br /> I8 13 Monitoring Activities <br /> Monitoring of vapor extraction systems involves weekly measurement of vapor concentrations at the <br />' inlet to the destruction unit and periodic service and repair Systems can be equipped with an <br /> automatic telecommunication system to alert the operator of system malfunction or failure Vapor <br /> samples should be collected monthly for laboratory analysis to monitor the efficiency of the <br /> remediation program When the concentrations of extracted vapor have decreased and stabilized after <br /> a certain period of operation, corif=ation borings are drilled to_collect soil samples for quantitative <br /> analysis in the laboratory to document the degree of cleanup obtained <br />' 8 14 Feasibility <br /> The radius of influence for SVE is generally defined as the distance from an extraction well at which <br />' an induced vacuum potential of at least 0 10 inches of water is observed (EPA - A Guide for <br /> Corrective Action Plan Reviewers) Generally, a vacuum of at least 0 10 inches of water is required <br /> to successfully volatilize subsurface hydrocarbons A vapor extraction feasibility test was performed <br />' at the site in December 1999 Based on a semi-logarithmic plot of induced vacuum measurements <br /> collected during the SVE pilot test from VW- 1, EW- 1 and MW-6 versus their distances.to VW-2 <br />' (extraction well), a theoretical radius of 13 feet is estimated(Figure 3) Based upon the results of the <br /> pilot test, it appears that SVE would be an adequate remediation alternative for soil at the site <br /> Based on the guide How ft411MM&Akernative Cleanup Technologies For UST Sites (October <br /> 1994)published by the United States Environmental Protection Agency(EPA) Office of USTs, the <br /> two most important factors that determine the effectiveness of SVE are permeability of the soil and <br /> volatility of the contaminant The guide further states that intrinsic permeability between the <br /> magnitude of 10 z cm/s and 10'8 cm/s and general volatility for gasolines are generally adequate for <br /> SVE technology(Exhibit 11-6 Intrinsic Permeability And SVE Effectiveness) Based on information <br /> t <br /> Advanced Ceoinvironmental,Inc <br /> I <br />