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20 March 1996 <br /> AGE-NC Project No 95-0130 <br /> Page 21 of 23 <br /> ' be between85 <br /> $ ,000 and $140,000 However, monitoring costs will vary depending upon regulatory <br /> ' requirements Additional inoculation events may be required to attain clean-up goals, which could <br /> significantly increase the total cost of the project <br /> Typical costs for monthly monitoring of an in-situ bioremediation system, in addition to standard <br /> quarterly sampling, would be between $1,500 00 and $3,000 00 per month Based on a one to two <br /> year treatment period, the total cost for in-situ bioremediation at the site would be between $100,000 <br /> ' and $200,000 <br /> 8.0. RECOMMENDATIONS FOR REMEDIATION OF HYDROCARBON- <br /> IMPACTED SOEL <br /> ' 8 1 FURTHER ASSESSMENT OF HYDROCARBON-IMPACTED SOIL <br /> Additional hydrocarbon-impacted soil may be present northwest of the former UST area and north <br /> of the site, on the former Wells Fargo property Several additional soil borings should be considered t <br /> for these areas to determine the lateral extent of impacted soil west of the UST area and north of the <br /> site <br /> ' 8 2 HYDROCARBON-IMPACTED SOIL REMEDIATION <br /> Vadose-zone contamination at the site is present in the immediate vicinity of the former UST <br /> ' excavation from depths of approximately 15 to 55 feet bsg However, "smear zone" contamination <br /> at the site is laterally more extensive, extending off-site north of the property <br /> ' Based upon feasibility studies and analysis performed at the site, we recommend an SVE system at <br /> the site The effectiveness of the SVE system should be evaluated on a semi-annual basis Based upon <br /> the relatively low flow rates measured during the SVE pilot test and the silty-clayey soil present at <br /> the site, a unit capable of at least 250 scfin will be required for remediation A thermal oxidation SVE <br /> unit will be the most cost-effective choice Vapor extraction at the site should be conducted in <br /> conjunction with ground water remediation (IAS) <br /> Additional SVE wells, with multiple screened intervals will be required at the site The wells should <br /> be screened only within zones of contaminated soil These wells have approximately 5 feet of screen <br /> above ground water and can be utilized to extract sparged vapors <br />