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City of Stockton Draft Amended Report of Waste Discharge(AROWD) <br /> Austin Road Landfill Work Plan <br /> This is a viable and cost-effective alternative if the two extraction wells,EW-1 and EW-2,are <br /> effectively intercepting the VOC contamination as it migrates past the downgradient edge of the <br /> landfill. <br /> Alternative 3—"Enhanced Source Control". The primary component of this alternative is the <br /> construction of an injection trench or injection wells at the approximate location depicted in Figure <br /> 3. Treated effluent from the on-site groundwater treatment plant is conveyed to the trench for <br /> injection into the unsaturated zone. This artificial recharge mechanism provides a hydraulic barrier <br /> to the movement of the plume in a downgradient,or north-northeast,direction. The creation of the <br /> hydraulic barrier improves the effectiveness of the two existing extraction wells in capturing the <br /> plume through the flattening of the general flow gradient. This impact on the gradient expands the <br /> capture zone of the two extraction wells,providing increased source control. In addition,aquifer <br /> recharge of clean water accelerates the natural flushing of the aquifer and reverses,on a small scale, <br /> the mining and overdraft pumping of the aquifer in the Stockton area. Enhanced source control <br /> could be implemented in addition to wellhead treatment. <br /> Alternative 4—"Downgradient Groundwater Extraction and Treatment". The primary <br /> component of Alternative 4 is the installation of one or more extraction wells in the plume <br /> downgradient of the influence of the two existing wells,EW-1 and EW-2. The location of the <br /> proposed wells will be determined through the application of numerical modeling. Use of the state <br /> agricultural well,or other existing wells,to achieve plume containment would be considered under <br /> this alternative. Modifications to the state agricultural well construction through the use of <br /> downhole perforation and installation of packers would be required to target specific aquifer zones <br /> for extraction. The suitability of testing the agricultural well as an extraction point cannot be <br /> determined until the plume extent is established. <br /> Additional components of Alternative 4 include conveyance piping to transport the groundwater <br /> back to the plant for treatment. Modifications to the treatment plant may be necessary to <br /> accommodate the increased capacity of groundwater requiring treatment. <br /> All alternatives will contain a component addressing institutional controls. Examples include deed <br /> restrictions,zoning controls,and other administrative measures. <br /> 5.0 Project Schedule <br /> The proposed schedule for the revised Corrective Action Program at the Austin Road Landfill is <br /> provided in Table 2. <br /> W:\REPORTS\STOCKTON\AUSTIN\WORKPLAN.DOC Page 16 <br />