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MINUTES July 29, 1993 3 BOARD OF HEALTH <br /> Mr. Dave Worden gave an overview of the study and <br /> stated, "Flat Pond is tidally flushed. " "I have detected a <br /> maximum of 6/10' fluctuation in Great Flat Pond. " "The water <br /> table is extremely flat and is only 4' deep. " "The area pro- <br /> posed for development is not within the recharge area to Flat <br /> Pond. " <br /> Mr. Doherty commented to Mr. Worden, "So what you are <br /> saying is that an effluent receptive system will either pass <br /> under or around the pond and will not actually infiltrate <br /> into the pond due to the peat and find sediment layer. " <br /> Mr. Worden responded, "Even if the fine sediment layer <br /> were not there, since the recharge area by definition is a <br /> land area which recharge to the pond originates, <br /> precipatation and discharges at points beyond that will flow <br /> underneath the basin and become incorporated into the under- <br /> lying transition zone with Nantucket Sound and slowly diffuse <br /> and however that transition zone functions move out with the <br /> general groundwater flow out to Nantucket Sound. " <br /> Mr. Ball questioned Mr. Worden as to how long that would <br /> take. <br /> Mr. Worden responded, "The USGS map indicates the tran- <br /> sition zone approaching 100' in thickness, I don't think the <br /> dynamics in that zone are well understood, but I think that <br /> anything that comes from a land area upgradient of the re- <br /> charge area does not intercept Flat Pond it becomes part of <br /> that transition zone through what ever processes occur there <br /> and slowly moves out to Nantucket Sound." <br /> Mr. Greelish questioned the groundwater flow rates in <br /> the area. <br /> Mr. Worden responded, "Horizontal flow rate is given at <br /> 1.4' per day and the vertical flow rate of .014' per day. " <br /> Mr. McQuaid questioned whether the estimated distance is <br /> from the edge of the proposed subdivision closest to the <br /> pond. <br /> Mr. Worden responded, "I think that is the estimated <br /> upgradient boundry of the recharge area 149' set back from <br /> i <br /> the shoreline. " <br /> Mr. Sherman questioned Mr. Worden as to how deep an area <br /> is the transition zone. <br /> Mr. Worden responded, "We did not bother to map the <br /> transition zone because it would require deep wells in the <br /> barrier beach. " "We are talking about an area that the <br />