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15 ,Tune 1999 <br /> . AGE-NC Project No 98-0450 <br />' Page 6 of 27 <br /> 32 ON-SITE EXTENT OF HYDROCARBON-IMPACTED GROUND WATER <br /> The inferred on-site extent of petroleum hydrocarbon-impacted ground water is presented on <br /> ' Figure 4 (February 1999) The petroleum hydrocarbon-impacted ground water is localized beneath <br /> the northeast portion of the site <br /> The core of the dissolved petroleum hydrocarbons appears to be limited to the site by wells MW-5, <br /> BMW-2 and BMW-5, as well as `grab' ground water sample from soil boring S132 The greatest <br /> concentrations of petroleum hydrocarbon compounds detected in ground water were in the sample <br /> ' collected from former UST area Reported concentrations of BTEX compounds in ground water <br /> collected from wells exceeded the MCLS for benzene of 10 /.cg/l, toluene of 150 µg/l, ethylbenzene <br /> ' of 700 µg/l, and total xylenes of 1,750 ug/1 <br /> ' 4 0. SOIL REMEDIAL ALTERNATIVES <br /> AGE evaluated various alternatives for remediation of petroleum impacted soil including ex-situ <br /> M treatment, soil vapor extraction, in-situ bioremediation, and natural attenuation Technology <br /> principles, feasibility and effectiveness, duration, and estimated cost are discussed for each of the <br /> remedial alternatives <br /> 41 EX-SITU TREATMENT <br /> ' <br /> Hydro acted soil can be excavated y p and treated on-site or transported off-site for <br /> ' recycling/disposal On-site treatment alternatives for excavated soil include aeration, bioremediation, <br /> vapor extraction, and thermal destruction, all of which are proven methods foi ex-situ remediation <br /> of soil contaminated with gasoline-range hydrocarbons Off-site disposal involves the transportation <br /> ' of the impacted soil to a licensed treatment/disposal facility <br /> ' 411 Principles <br /> Ex-situ treatments and off-site disposal alternatives require excavation of the impacted soil <br /> ' = Mechanical equipment such as a backhoe or an excavator are generally used to excavate soil Once �- <br /> excavated, impacted soil is generally stockpiled on-site for treatment or transported off-site for <br /> disposal If impacted soil is treated on-site and hydrocarbon concentrations can be reduced to <br /> ' regulatory agency-acceptable clean-up levels or to non-detectable concentrations, treated soil may <br /> be used to backfill the excavation If hydrocarbon-impacted soil is disposed of off-site, fill material <br /> must be imported to backfill the excavation <br /> Advanced CeoEnN ironmenla),the <br />