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1 <br /> 20 March 1996 <br /> AGE-NC Project No 95-0130 <br /> Page 22 of 23 <br />' 9.0. RECOMMENDATIONS FOR REMEDIATION OF HYDROCARBON-IMPACTED <br />' GROUND WATER <br /> 91 ADDITIONAL ASSESSMENT OF HYDROCARBON-IMPACTED GROUND WATER <br />' The data indicates that the extent of impacted ground water north of the site has not been determined <br /> Also, there is the possibility that a secondary source of impacted ground water may be present north <br />' of the site Additional monitoring wells will be required north of the site to determine the lateral <br /> extent of impacted ground water or the presence of a secondary contamination source We <br /> recommend the installation of two additional ground water monitoring wells north of the property <br />' on the former Wells Fargo Bank site <br />' 9 2 HYDROCARBON-IMPACTED SOIL REMEDIATION <br /> Soil and ground water remediation should be conducted concurrently at the site to prevent re- <br /> contamination of remediated soil Impacted ground water is present off-site to the north, east and <br /> southeast of the property <br />' "Pump and treat" will be too costly, based upon the lateral extent of the dissolved hydrocarbon <br /> plume Furthermore, It Is unlikely that background hydrocarbon levels (clean-up goals) could be <br /> reached with a "pump and treat" method Pumping tests would also have to be performed to <br /> determine aquifer characteristics Therefore, we recommend an in-situ method for ground water <br /> remediation at the site <br /> IBoth SVE/IAS and in-situ bioremediation provide methods for remediation of soil and ground water <br /> concurrently IAS combined with an SVE system would effectively reduce dissolved concentrations <br /> of shorter-chain hydrocarbons (gasoline) In ground water <br /> In-situ bioremediation of ground water may be cost-effective, but as with in-situ bioremediation of <br /> I soil, special monitoring requirements Imposed by many regulatory agencies can significantly reduce <br /> the cost effectiveness of the method Furthermore, bioremediation feasibility studies have not been <br /> performed on ground water at the site, however, based upon preliminary physicochemical analysis <br /> and microbial enumeration of soil samples from the site, bloremedlatlon of ground water may not be <br /> effective at the TFS site <br /> Combined with SVE, an IAS system"mechanically/physically" strips hydrocarbons without the need <br /> of adding any chenucals or microbe solution into the environment It Is a better known and more <br /> widely accepted method of volatilizing hydrocarbons with few, If any, adverse environmental effects <br /> Based upon these considerations, and assuming that dissolved Iron concentrations at the site are less <br /> than 20 ppm, we recommend the Installation of an IAS system for remediation of ground water at the <br />