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Project No S8080-06-02 <br /> May 5, 1995 <br />' in much less time and at much lower cost using a targeted VES, the full scale VES option will not <br /> be given further consideration <br /> 5 8 Targeted Vapor Extraction <br />' The risk of future groundwater impacts beneath the site are due to the presence of BTEX within the <br />' soil hydrocarbon plume beneath the southern portion of the site More specifically, the presence <br /> of BTEX in soil between the depths of approximately 28 and 43 feet bgs in the vicinity of boring <br /> GB-5 presents the greatest risk of future groundwater impact The operation of a vapor extraction <br /> 1 system designed to target the BTEX portions of the plume would provide the following <br /> environmental benefits <br /> • Removal of the remaining residual BTEX in soil beneath the entire site <br /> • Removal of significant additional amounts of TPI-Ig from soil beneath the site <br /> • Reduction in the volume and mass of the soil hydrocarbon plume <br /> • increased distance between TPHg in soil and the groundwater surface <br /> • Minimization of the future risk of groundwater impact due to a rise in the,groundwater <br /> ' surface <br /> A limited vapor extraction system designed to target the BTEX portions of the plume would <br /> necessitate extraction from VW-3, VW-4 and VW-5 at an estimated combined flowrate of <br /> approximately 100 scfm It is estimated that remediation of the BTEX portion of the plume will <br /> ' require approximately 12 months of extraction at a cost of approximately $100,000 <br /> -29- <br />