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10f12f1998 16:@9 9165350207 APEX ENVIROTEOH PAGE 25 <br /> S✓ '+ <br /> po <br /> source Treatment Applications#�P CatiC►nS - Saturated Zone <br /> RA QUN <br /> URC may be used upgradient, near the original source of contamination to retract the plume <br /> towards the source, permitting a compliance point closure to be met. In this application ORC can <br /> be used to address contaminant loads in the higher dissolved phase range (10-100 Ppm). <br /> URC may be applied to the subsurface in completed monitoring wells that allow the use of <br /> exchangeable filter sacks, or by the use of direct push or augered holes into which;a grout-like <br /> slurry of URC is applied. When an excavation of the source 'areas is planned„there are soil mixing <br /> application$ that cart be considered using ORC'powder; these applications are considered <br /> separately in Technical Bulletins 2.1,2, 23»?, and 2.12. <br /> 1AEP 1.1-CAT-M- <br /> The ORC applications discussed are directed at site closure. With new regulatory guidelines i <br /> process closure may be achieved as a function of the compliance requirements which will range <br /> from MCL to ROCA standards. In a ROCA framework, risk reduction is tied to mass reduction such <br /> that attenuating the source will allow target levels at the compliance paint to be achieved. <br /> The "near field zone" is the primary target for ORC application. We define the near field zone as <br /> the dissolved phase and the sorbed material located within the saturated zone and capillary <br /> fringe. Smear zones can be treated as an additional measure to guard against recharge to the near <br /> field zone. NUTS: source areas that have free product are not amenable to URC applications. The <br /> application of URC in the vadose zone is under development. <br /> M"CO M <br /> HeGENESM staff Is available on request to help in planning a source treatment application. for <br /> illustrative purposes we will consider two different ORC application scenarios. <br /> SCENARIO 1: <br /> Ret»cdilrt._Oblte�ctrr e: Remediate the source area to MCI- or RSCA Standard. The compliance point is <br /> within the source area, <br /> Dissolved Phase Contaminant Level: '10 parts per million <br /> Ground '►+bate. Velocity: 0.2 foot per day <br /> Near Field Sorbed'Mass Factor: <br /> Source Area Dimensions: So feet x So Beet <br /> Contamirmted Saturated'Zone. 15 feet <br />