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4. <br /> 27 August-2002 <br /> p• <br /> AGE-NC Project No.-95 0142 �� Y <br /> r { ys � � E_ -p-� <br /> Page 2 of 3 r <br /> In addition, since:ground"water levels have risen: approximately 20 feet, the-effectivertess of <br /> r proposed soil vapor .extraction with in-silo air sparging'(SVE/IAS) as a standalone treatment <br /> system has'decreased due to.the substantialv_mc ase in-saturation of impacted soil_and,the resulting <br /> decrease of exposed soil.: 3 <br /> The impacted soil is-!;- nariI - fine-grained,zwhich may make the upward and lateral path of <br /> sparged=air-through the sat_izrated zone unpredictable and the stripped Hydrocarbons unrecoverable <br /> `With the majority of the mass of impaeted soil-now-in the--=saturated_:zone, ,�a more aggressive- <br /> approach i5 required.:'IAS-is.apassive method which relies on-the rh vement-of air upwards into a ',j <br /> - zone of lower perm eability.:=The3irriited`over. ef. e(tiveness'�and°reliability ofV' AS tedhriology-to <br /> remediate, mpacted soiYand:grourid:water'requires`xe-.evaluation of.the .method proposed;in the <br /> CAP: F _ <br /> - <br /> _ AGE has operated-five-IAS-systems in Stockton•tjver the past three years,none of whrch have been <br /> - effective in remediation of dissolved or=-adsorbed hydrocarbons :;Three of these sites::are:within L <br /> .. . <br /> 2,000-feet,of-the Stockton Plating-location and have sinulaf geologic conditions; One of these sites <br /> has sirice.been'.switche' d over to aground ,Water extraction treatment-system:at the request of the 4 <br /> Y EHD office and the.C'alifornia Regional'Viter Quality Control_Board, after:only a'SO percent 4 <br /> R reduction in hydrocarbon mass byIA5:Tlie`remairiing two sites utilized'IAS and SVE to'a point of i0F' <br /> diminishing returns, however, no ."siguficaht. reductions of hydrocarbons have .occurred in the-,:' <br /> ground water.: <br /> A. <br /> AGE recommended the use of ground'water=extraction as an`al ternative.metho54 <br /> d for ground water:. r <br /> rerriediation techni ue:at-th_e site in the;Final Remediation-Plan RP dated 23 A rtl 2002. AGE ~ <br /> believes that a .ground' water.-:extraction system-is a betterwalternative;than IAS based. on the_'' Y 1" ' <br /> - :following: ., - <br /> , <br /> w Although.AGE_did'noYperform'a pilot".test.;of IAS at the Stockton Plating 'site,the-fine�grained <br /> 'j, <br /> nature of the soil as well a' tion,effectiveness of 1AS at sites nearby suggesf:that this. ' ethod is = <br /> not a viable-alternative - <br /> Soil clean-up is expected-to.be=completed-by.SVE In 12•to 1$ moriths,(Table 1).-.-Part of an <br /> _ IAS system is tYie:use-of an:SVE unrt-to:remove anti destroy vapors generated by.IAS: Based <br /> ori.the two year long IAS projects that AGE has opeiated:iiearkiy,_.it.is likely±that-aix sparging at {"} <br /> this site could range.frorm-36-;to 60 months To operate the SVE`=_system for' additional 24 to.. <br /> 4$ months in conjunction with IAS would not cost-effective(Table:l)" = _ 5 <br /> The limited areal distribution of high coricezitrations>of dissolvedhydrocarbons near the sourced _z . <br /> of the.release favors an;aggressive appioachffar removing the dissolved'.hydrocarbon on-site <br /> A ground water.eXtracti6ft system in the- source area,arid_ along the historical down_ -gradient <br /> Advanced GeoEnvironmental,Inc. x <br />