2020-07-13-CONCOM-min - Laserfiche WebLink

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As an alternative, they are evaluating the potential for stormwater mitigation associated with Hartwell Place itself. The engineering department, on a recommendation of the Conservation Director, shared an existing concept developed with guidance and assistance from the UNH Stormwater Center involving providing mini stormwater retention trenches that are designed to pick-up isolated inflows from catch basins. The trenches partially rely on infiltration and are also subject to groundwater conditions. As next steps, they are conducting test pits within the Hartwell Place layout to help provide data to further evaluate this method. John Kastrinos, hydrologist from Haley and Aldrich, presented a brief update before the Commission. He stated he has not had a lot of time to look at the soil data but has reviewed some of it and may recommend some revisions to the elevations but is reserving full comments until he has had an opportunity to study and evaluate the information and the site based on his professional knowledge and experience. Mr. Brassard from Judith Nitsche responded that they feel confident in their approach and believe very conservative but they are also prepared to rerun the calculations if Mr. Kastrinos recommends raising the groundwater elevations by 6-inches, and they are confident that the wet basins will still be adequately sized. Concerns of the Commission: - The sediment forebays base plan calls them to be cleaned out twice a year. Where does it say what to look for when assessing clean out of sediment deposit(such as depth)? - Inspection checklist provided. It is missing the wetland replication area and wet basins. - Obtain third party opinion on test pits and groundwater level. Responses of the Applicant: - They can be more explicit in terms of outlining that. - They can update that and provide more detail. - They did retain services from a hydrologist and will have further information at the next meeting. On a motion by Ms. Samuels and seconded by Ms. Ladd, the Commission voted 7-0 by roll call vote to continue the hearing until July 27, 2020 at the applicant's request. Record of vote as follows: Philip Hamilton—Aye Kevin Beuttell—Aye Alex Dohan—Aye Ruth Ladd—Aye David Langseth—Aye Holly Samuels —Aye Duke Bitsko —Aye Ch. 130 Regulation Amendments: Rules Section 5 Performance Standards: Section 5(5) Buffer Zone The Commission reviewed the Draft Buffer Zone Regulations dated 2/3/2020. Proposed