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1 <br />' 10 June 1999 <br /> i AGE-NC Project No 97-0290 <br />' Page 1 i of 26 <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 /> (1 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 />' 7 13 Monitoring Activities <br /> Monitoring of vapor extraction systems involves weekly measurement of vapor concentrations at <br />' the 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 Soil gas <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, confirmation borings are drilled to collect soil samples for quantitative <br />' analysis in the laboratory to document the degree of cleanup obtained <br /> 7 1 4 Feasibility <br /> The radius of influence for SVE is generally defined as the distance from an extraction well at which <br />' a vacuum of at least 0 1 inches of water is observed (EPA - A guide for Corrective Action Plan <br /> Reviewers) Generally,a vacuum of at least 0 10 inches of water is required to successfully volatilize <br /> subsurface hydrocarbons A vapor extraction feasibility test was performed at the site in May 1999 <br />' Based on a semi-logarithmic plot of induced vacuum measurements collected during the SVE pilot <br /> test ram MW2, MW 1 and va or oints] versus their distances to V W 1 (extraction well), a <br />' theoretical radi�the <br /> rox�thc <br /> Opi . <br /> �es , <br /> estimated at a vacuum of 0 1 inches of water (Figure <br /> 10) Based upoesults t appears that SVE would be an effective remediation <br /> alternative for soil at the site <br />' Based on the guide How to Evaluate Alter native 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`2 and 10 s and general volatility for gasolines are generally adequate for SVE <br />' technology (Exhibit II--6 Intrinsic Permeability And SVE Effectiveness) Based on information <br /> gained through fate evaluation laboratory analysis, the permeability at the site ranged from 3 5 x 10' � <br /> to 3 3 x 10' Results of the fate evaluation laboratory analysis indicated permeability conditions at <br />' the site are adequate for SVE <br /> • Based on geologic cross sections(Figures 4 and 5), soil beneath the former UST area has a relatively <br /> 1 <br /> Advanced GeoEnNironmenlai,Inc <br />