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, S t t If I I 14 November 1995 AGE-NC Project No 95-0121 , ' Page 19 of 20 ; ` We recommend the implementation of a phased-remediation approach at the site Initially, an SVE ' system will be installed and operated at the site 'The effectiveness of the SVE system will be evaluated on asemi-annual basis°If after one year of operation the SVE system does not indicate a concentration decrease of longer-chem hydrocarbons; active biostunulation/bioenhancement will "` -` '" be I initiated Hydrocarbon-degrading bacteria and,nutnents will be added to the soil, and ground water, if necessary I E Based upon the relatively low flow rates measured during the SVE pilot test and,the silty-clayey soil present at the site, a unit capable of at least 250 scfm will be required for remediation A thermal toxidation SVE unit will be the most cost-effective choke Vapor extraction at the site should be conducted in conjunction with ground water remediation (IAS) ' We estimate that six additional SVE wells will be required at the site ~The wells shouldbescreened only within contaminated zones of soil At least one well will be required off-site, northeast of MW-4, to facilitate ground water remediation In addition to the SVE wells, monitoring wellsMW-4, MW- ' 5 and MW-6 should be included in the extraction system network to assist ground water remediation a through in-situ air sparging These wells have approximately 5 feet of screen above ground water and can be utilized to extract sparged vapors Proposed vapor well locations are illustrated on Figure 5 Soil samples collected during the installation of SVE wells should undergo physicochemical analysis Iand nucrobiological enumeration to,determme baseline bioremediaiton parameters 9.0. RECOMMENDATIONS FOR REMEDIATION OF HYDROCARBON-IMPACTED ' GROUND WATER ) I , ' Soil and ground water remediation will ibe conducted concurrently at the site to,prevent re- contamination of remediated soil Impacted ground water is present off-site south, `east and'west of the Nomellini property, ' - "Pum and treat" to,be too costly,based upon the lateral extent of the dissolved hydrocarbon P appears plume Furthermore, it is unlikely that cleanup goals could be reached with a "pump and treat' ' method � Pumping tests would also have to be performed to determine aquifer characteristics Therefore, we recommend an in-situ method for ground water remediation at the Nomellini,site Both SVE/IAS and bioremediation provide methods for remediation`of soil and ground water concurrently IAS combined with an SVE system would effectively reduce dissolved'concentrations of shorter-chain hydrocarbons(gasoline) in ground water However, longer-chain hydrocarbons are ' not effectively remediated `using an IAS system I' 1 5 t, i ! ♦ v , I sjl 11 4 N , ,