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MINUTES LEXINGTON CONSERVATION COMMISSION 8/8/00 PAGE 6 delineated by using data of the original submission of four years ago. At that time, the delineation of the wetlands for that submission was under question by abutters and they filed legal documents countering what had been established as the wetlands, but when the submission was withdrawn,they were told that that submission was moot. So the establishment of the wetlands should be based on current data from the last submission. Barbara Newman asked what assurance there is that the replication will take. Joyce Miller said she believes the failure rate is very high. Paul Newman, (Blueberry Road) submitted an addendum to his submission of August 2nd for the record. He does not believe that the stream today would look like the video taken in 1998 as of September 2. (Mr. Wolk confirmed that the stream had ponding water around A-10, he was not sure if it was running or not.) In the submission of August 2, 1998, it was stated that that year was the wettest rainfall year on record (15" of rain in June) and it is hard for him to believe that it came from a 1998 site visit of that stream. As detailed in his submission, he doesn't believe the stream dries up. He said that if the detention pond discharge data is correct, the minimum flow for a 10-year 24 hour storm would be 5 feet per second. This would be excessive for a soil based channel. It should not exceed 2.5 feet per second. Regarding lining the channel with rip rap, it is not appropriate for a wetland replication area because rip rap heats up and it will cause pre-thermal pollution which will cause the water to be too hot in that resource area. The velocity of water that comes out of the detention pond should be corrected. The manicured lawns will be a concern with the herbicides, etc. Is the replication area a replication area under 310 CRM 10 or is it a BMP? They propose a braided channel outlet from a detention pond through their replication area. The law states that a replication area has to replicate the functions and values of the wetland area being destroyed. There is no a replication area on the premises because a detention pond is used for collecting stormwater runoff. They state that the detention pond will discharge into their replication wetland and it will provide further cleansing of this contaminated water. He believes this is a stormwater management structure (a BMP) and there will be no standing water in it at all. They are offering only a 1 1 replacement on the premises. With at least 2:1 replication the success rate of replication is only about 12 to 50%. There are several types of streams, but he thinks this channel is a drainage way because it accommodates stormwater runoff. He believes the wetland at the top half of the parcel is not a braided stream channel, but a wooded swamp with an intermittent stream. It is proximate to the underground gnurreLwatertorthat_stream_whichis_the_spring_from_the-split-rocic and-also-serves-as-the surface water supply during the times of year when it is inundated. You have to recreate the same value and function of the wetland that is being destroyed. For a small wetland you need two water courses like this to recreate a headwater supply that discharges cool spring -like waters into this stream, so that this stream continues to flow as much as it does today There is no provision for overflow from the infiltrator units on the lots. They will require maintenance if they become clogged. They are close to the foundations of the houses which may be compromised and this may cause erosion of the steep slopes and everything will erode into the wetlands. Another major problem is that this is a small watershed and depends on all of its parts. He believes the detention pond will collect the majority of the stormwater runoff and it will discharge from two points instead of around the wetland. This water will flash off the premises and no longer be infiltrated into the ground and be slowly recharged back into the stream and the wetland system. The depth and time of saturation of the wetland system will be changed and degraded.