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MINUTES LEXINGTON CONSERVATION COMMISSION 8/8/00 PAGE 3 Phyllis Etsell of Winning Farm Trust, submitted for the record a copy of the Corrective Action design plan for Woburn/Winchester and a letter from Vertex Engineering regarding the BU Report. A video of Dr. Sanford's and Ms. Etsell's walk through the resource area was shown. The purpose of the video was to show that when Dr. Sanford walked the property on August 7, 1998, and when Ms. Etsell walked on the land on September 9, 1998, the stream channel was dry Signed affidavits to that effect were submitted. A keyed map was used to illustrate the locations shown in the video. Ms. Etsell has walked the land six times and found water in the stream channel only once, on June 17, 2000. Ms. Baci took exception to this for she recalls the stream was not dry during a Commission walk a couple of years ago and Mrs. Miller and Mrs. Frick agreed that they have seen the channel when it was not dry On the video Dr. Sanford noted an intermittent system in the area of the proposed crossing. There is a black area surrounded by the wetland vegetation; the flow appears to break into a network of channels that go through areas of humus and hollows at various points. In an area where the terrain was flat he could not tell if the water just ponds or if there is a flow He will treat this area as if it were bank with flow Their wildlife habitat assessment will be conducted in this area. Ms. Etsell continued the narrative with the second portion of the video which started at Flag A2. The area of the stonebound at the beginning of the property was shown with no flowing or standing water. They traveled through the middle of the resource area which was thick with brush and vegetation; she said the line was accepted by the Lexington Conservation Commission. She found dry areas and small areas of puddling. Near Flag A5 there was no evidence of puddling and the area was dry Ms. Etsell submitted the video as evidence that the channel was not flowing. Mrs. Miller read the Engineer's report with comments to be addressed by the applicant. Mr. Miller said he has talked to Mr. Hayes, the Town Engineer, and said that Mr. Hayes did recognize the fact that the correct number is 70 infiltrators and not 84 There was no detail for the weir because it was intended to be an earthen weir and left natural. It was designed as a detention pond to hold water and there will be less than 2 inches of overflow during a 10-year storm. It has less than 2 feet of overflow during the 100-year storm. Water will not flow over it on A consistent_basis_Mr.,Miller does notbelieve_itneeds-to-be-riprappedrbut-if-requiredrit-car be done. The 4-inch pipe at the bottom is to drain it over a period of time and will not cause erosion problems. Percolation testing has not been done but can be done. The infiltration system is not designed to assume any infiltration, but designed for storage volume of roof runoff. It could function as designed and water would percolate into the ground over a long period of time, even if it is a D soil. More relevant is the issue of the groundwater level, if it is too high, there will not be any percolation. The groundwater is at least 2 feet below the bottom of each of the infiltration systems. He believes each of the infiltration systems will work as designed. Water will infiltrate in a D soil, but it will take longer than in an A soil. The soils maps show the area to be a D soil. They did tests but to make it a conservative design they assumed there was no infiltration. Test pits were dug to determine the high groundwater elevation, but they did not classify the soils.