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Board of Selectmen <br /> Minutes <br /> l April 6, 1998 2 <br /> Lowell Holly peninsula. He presented a map showing the locations of monitoring wells. <br /> Mr. Martin also presented a map of groundwater elevations. A lot of groundwater flow <br /> modeling information is available for this area. <br /> Selectmen Marsters asked why the plume gets wider, as it heads towards the Pond, if <br /> groundwater is not flowing north? <br /> Mr. Martin explained the pond flow is pulling it and causing a"fanning out" of the plume. <br /> A question was asked what the actual concentration was in surface water samples? <br /> Mr. Martin said the highest was under 5 parts per billion of PCE. <br /> Selectmen Caffyn said to be able to grab a contaminated sample in the pond is a serious concern. <br /> They have been unable to do that in Johns or Ashumet Pond. It indicates a lot of contamination is <br /> under the pond. <br /> Mr. Martin explained the feasibility study for cleanup alternatives was completed in December. <br /> The consultants reviewed 14 major technologies available, with 46 variations. The results are <br /> two feasible technologies: recirculating wells and groundwater recovery and treatment. <br /> Recirculating wells: the contaminant present in the plume does not come out of groundwater <br /> easily. This would decrease the efficiency by 40% and lengthen the time. <br /> Groundwater recovery and treatment: liquid phase carbon absorption. 2 recovery wells will be <br /> installed along the axis of the plume. Treated water will be discharged into Mashpee Wakeby <br /> Pond. The size (small, narrow, dirt) and topography of Cove Road make it difficult to install a <br /> recovery system. DEP has access for wells and piping near Hirsch Road, a paper, dirt road with <br /> adjacent 17 acre parcel. <br /> A portion of the plume will be cut off and will continue to migrate towards the Pond. It was <br /> determined that the total mass of that portion of the plume would not have a human health <br /> impact. More research needs to be done to determine the ecological risk. An ecological risk <br /> assessment will be conducted. <br /> Selectmen Marsters asked what percentage of the plume that is (that will be cut off)? <br /> Mr. Martin said it is a small percentage. <br /> DEP would like to get recovery wells in the ground before the end of June and begin to get the <br /> contamination out of the groundwater. They plan to begin that and do the ecological impact <br /> study at the same time. <br /> Selectmen Caffyn does not think 2 recovery wells seems like enough to really draw the plume. <br /> Also, she is concerned there is a lot of the plume that do not plan to stop. <br /> Mr. Martin said they are not totally writing that off. They'ust received this report on Friday. <br /> Question: does DEP anticipate the pumping and recovery will have any effect on the <br /> groundwater level? Mr. Martin said you will see some drawdown in that area. <br />