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f <br /> total of approximately 9J <br /> 3 extraction and reinjection low. Institutional controls will prohibit d <br /> wells,and S recirculating atin wells. new wells within, or in the direct path of, t <br /> groundwater plume. Residences over of <br /> Matrix Criteria downgradient of the plume have beet <br /> he scheduled to be connected to public watt <br /> Overall Protection of Human Health and t ate controls on <br /> • • e human health There may not be adequate <br /> Environment: Under this alternative, <br /> ed because a high percentage of the wells. <br /> would be protect <br /> g <br /> groundwater plume is captured, further migration of Effectiveness of Treatment Systems: <br /> contaminants is greatly reduced, and institutional portion of the treatment system is cE <br /> controls will minimize future exposure to contamiremoving VOCs and EDB to below detecti <br /> pants. <br /> Institutional controls include prohibiting other contaminants, such as semi-vola <br /> drilling of new wells within, or in the direct path of, inorganics, would also be treated to N <br /> the CS-10 groundwater plume. Much of the plume levels, if.technically and economically f <br /> that might otherwise migrate under or into Ashumet they appear in the extracted water <br /> and Johns Ponds would be captured. . Contaminant recirculating wells remove only VOCs an <br /> concentrations downgradient of the system south of effectively remove EDB, semi-volatile <br /> Sandwich Road are reduced by recirculating wells. organics without additional above-ground <br /> • t because which are not included in this alternativ <br /> Hydrological thresholds would not be met, contaminants are not anticipated in the <br /> the amount of treated water that flushes through the <br /> }, the recirculating wells. If EDB, semi-vc <br /> i <br /> ponds s anticipated to be slightly above the <br /> well pilot inorganics are detected in the plume <br /> threshold. However, the recirculating p , , <br /> t si Hifi- requiring action, additi <br /> onal treatment systc <br /> study suggests that treated water will no g <br /> tl alter ambient water quality. In addition, it is be added. <br /> can y q tY <br /> believed that final design could bring Ashumet Pond Spent carbon produced :by the system <br /> treated water flows within guidance thresholds. transferred offsite for regeneration, whirl <br /> System construction would affect sensitive habitats the contaminants. Residual solid wastes <br /> and rare upland animal species. Impacts to transferred offsite and disposed of in an a <br /> Ashumet Pond habitats would be reduced by using manner. The residual solid wastes are no <br /> recirculating wells. The remaining impacts would to be a hazardous waste. Risks tc <br /> require moderate mitigation. associated with handling, treating, and di <br /> re <br /> isiduals would be low. The alternative <br /> Compliance wth Applicable or Relevant and <br /> iAppropriate - statutory preference for treatment as a <br /> Re Requirements This alter <br /> native complies with all ARARs. element. <br /> Effectiveness and Permanence of Response Alter- Implementability: Full system startup w <br /> • The table on page 3 summarizes plume <br /> by the EPA-enforceable milestone of Jun( <br /> natives, p g p <br /> capture by mass for all alternatives. A similar table Partial system startup may be achieval <br /> summarizing plume capture by <br /> volume is included in Sandwich Road extraction fence in les <br /> months from the decision date, given ftthe matrix document. <br /> regulatory approval. It is estimated that <br /> Under Alternative C, 98 percent of the contaminants y <br /> will operate for at feast So ears. <br /> (by mass) is captured by the treatment system or accepted, proven technology that can be <br /> caught in silts. The System effectively removes <br /> perform reliably with proper <br /> m, <br /> ' would have a p y p p <br /> contaminants, and the configuration Recirculating well technology is used <br /> minimal effect on other plumes. A small percentage contaminant mass removal south of Sand, <br /> (2 percent) of the contaminant mass would not be Because ETR is araven technology, <br /> captured or caught in silts; however, human health P <br /> cap g ' agency involvement to obtain approv, <br /> and ecological risk associated with that portion is <br /> minimal. <br /> very low. <br /> Most of the ETR wells would be installer <br /> Socioeconomic impacts associated with the <br /> . property, greatly simplifying access to <br /> uncaptured portion of the plume, such as impacts on tions. Recirculatingwells, however, <br /> commercial or residential interests recreation and <br /> ' installed on private property between <br /> historical and archeological sites, are expected to be <br /> 6 <br />