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CS-'Io FLUME RESPONSE ALTERNATIVE C1 <br /> Alternative C I uses a combination of ETR and ■ Specifically designed to minimize disturbance <br /> recirculating well technology(RVvTT). It is designed to the Ashumet valley plume. <br /> to improve plume cleanup, with some consideration <br /> f Sandwich Road Extraction Fence <br /> of property ownership, access, and ecological im- <br /> pacts. Extraction fences would be located along the ■ Captures the portion of the CS-10 plume up- <br /> leading edge of the plume, except for the area adja- gradient of Sandwich Road. <br /> cent to Ashumet Pond. Recirculating wells would Ashumet Pond Recirculatin Wells <br /> be placed near the edge of the pond and extraction <br /> ells would be laced aloe Sandwich Road. • Captures some of the plume downgradient from <br /> w p g <br /> Sandwich Road and upgradient of Ashumet <br /> The attached figure illustrates the conceptual layout pond. Property access issues would not allow <br /> P <br /> of ETR fences and recirculating wells for Alterna for spacing of recirculating welts sufficient to <br /> ' <br /> tive C I,described below. p g <br /> achieve complete capture. <br /> f the �Iternat� ►eCom <br /> Components 0These wetly are expected to operate only 3-5 <br /> Northwest Extraction Fence years. <br /> ■ Improves capture of a portion of the plume East Rein'ection Fence <br /> north of the fence that is relatively highly con- ■ Balancesoundwater flow b Y returning some <br /> � <br /> taminated, preventing some contaminants from of the water that would be intercepted by the <br /> migrating to low-conductivity silts. Sandwich Road extraction fence. <br /> ■ Minimizes impacts to groundwater flow direc- ■ Balances the reinjection of water west of the <br /> tions for the adjacent LF-I plume. CS-1 p plume. <br /> ■ Reinjection fences are not located near the Considerations <br /> northwest extraction fence. This strategy avoids <br /> the potential for spreading the f b rein- <br /> jecting cleanup/massplume treated water over the-plume. ■ Installation and operation of recirculating wells <br /> Southwest Extraction Fence near the Ashumet Pond shoreline results in <br /> fewer ecological and socioeconomic impacts <br /> ■ Captures the western lobe of the plume. than extraction wells. <br /> ■ Captures the upgradient portion of the CS--4 and The portion of the plume between Sandwich <br /> FS-28 plumes. Road and Ashumet Pond would be subject to <br /> West Rein'ection Fence contaminant mass reduction, but some of the <br /> plume would not be captured and could migrate <br /> ■ Balances groundwater flow by returning treated <br /> to and/or beyond the pond, <br /> water to the aquifer removed by the northwest <br /> and southwest extraction fences. ■ The installation of recirculating wells could <br /> • affect sensitive ecological habitats adjacent to <br /> ■ Specifically designed to minimize disturbance the pond, requiring some mitigation procedures <br /> of the LF-I and CS-4 plumes. and plans. <br /> Southern Extraction Fence ■ There is ap otential socioeconomic impact asso- <br /> ■ Treats the centralp ortion of the plume. ciated with the installation and operation of the <br /> • recirculating well system in the residential area <br /> n R <br /> Maiein ection Fence southeast of Sandwich Road. <br /> ■ Balances groundwater flow by returning treated It is possible that gaining ainin access to all of the <br /> ■ <br /> water to the aquifer removed by the southern required properties could delay the installation <br /> extraction fence. and startup of the recirculating well element of <br /> the system. <br /> 3 <br />