8/19/1997 BOARD OF SELECTMEN Minutes

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Plume capture b volume is included in Sandwich Road extraction fence in less than 12 surnm�'rr��rng p p Y the matrix document months from the decision date, given funding and 3 regulatory approval. It is estimated that the system Under Alternative B, has the 98 percent of the operate for at least 50 ears. ETR is an . ' the treatment will op y contaminants Eby massy is capture y accepted, coven technology that can be expected to tin silts. The system effectively P 'P � system or cough Y y contaminants, and the configuration would Perform reliably with proper maintenance. Because removes it is a proven technology, regulatory agency have a minimal effect on other plumes. A small involvement to obtain approval will be minimal. Percentage of"the contaminant mass 2 percent) .would not captured tured or caught in silts; however, Access to property to install wells would be sim- P health and ecological risk associated with plified because the majority of wells would be hum an g that portion is very low. installed on MMR property. P • Socioeconomic impacts as g associated with the Manageable risks to human health are anticipated - unto tured portion of the plume, such as impacts on during construction and operation of the system. P commercial or residential interests, recreation, and Treatment plants would be located on base, thus historical and archeological are ex rcheolo ical sites ected to be minimizing potential risks to the off-base neighbor- low. low. Institutional controls will prohibit drilling of hood. new wells within, or in the direct path of, the CS-10 acts to rare habitats are expected but Adverse imp P groundwater plume. Residences over or directly can be mitigated with a moderate level of sched- uling g downgradient of the plume have been or are and construction planning. The impacts asso- nnected to public water supply. • scheduled to be co P PP y crated with construction along the Ashumet Pond There may not be adequate controls on existing shoreline and the Northwest Extraction Fence would wells. be eliminated for this alternative. Effectiveness of Treatment Systems: The treat- Construction and operation would cause low socio- meat system.is capable of removing VOCs and EDB to below detection limits. ether contaminants, such economic impacts on the residential neighborhoodnear Ashumet Pond because most construction and as semi-volatiles and inorganics, would also be operation would take place on base. round levels if technically p treated to background y and ' l feasible, if the appear in the fast: Total capital cost is estimated to be $39.8 economically , _ Y pP i extracted water. Spent carbon produced by the million. Annual operating and maintenance cost s regeneration, estimated to be $3.4 million. s Life-cycle cost, system would be transferred offsite for re g , which destroys the contaminants. Residual solid including capital cost, based on 20 years of opera- wastes would be transferred offsite and disposed of tion(for cost-estimating purposes only) is estimated o P in an a ro riate manner. The residual solid wastes to be$108 million. PP P are not expected to be a hazardous waste. Risks to Public Acceptance: The public acceptance of all workers associated with handling, treating, and the response alternatives will be determined disposing of residuals would be low. The throughout the public comment period. The respec- alternative satisfies a statutory, preference for tive or anizations, agencies, and community groups g treatment as a principal element. (acceptance tante groups)will review the information and Implementability: Full system startup would begin indicate a preferred choice, acceptable second and by EP the enforceable milestone of June 28 1999. third choices,and any unacceptable alternatives. A- Partial system startup may be achievable for the CSm10 PLUME RESPONSE A Alternative Ccombines ETR and recirculating well and recirculating wells to reduce contaminant mass- gY technolo , This alternative is designed with con- between Sandwich Road and Ashumet Pond. sideration of property access issues and potential The system would operate at a total flow rate of y . adverse impacts to sensitive ecological areas along approximately 7.5 mgd, and would include the shoreline of Ashumet Pond. Instead of an approximately 35,000 linear feet of i in and a . PP • y P P g� extraction fence along the pond, this alternative would use an extraction fence along Sandwich Road 5