2021-03-29-CONCOM-min - Laserfiche WebLink

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Project: Kiln Brook culvert daylighting. An existing 36" RCP drain pipe that discharges to Kiln Brook will be converted to an open stream channel, including a stone lined channel, native vegetation plantings, a vegetated retaining wall, and an 8'x4' box culvert. Documentation Submitted: — Plans; Figure 1: Locus Plan; Figure 2: Existing Conditions Plan; Figure 3: Proposed Plan Layout; Figure 4: Section A/4 Typical; Figure 5: Centerline Section for Stream Daylighting; Figure 6: Erosion Control Details; Prepared by: Environmental Partners Group; Stamped and signed by: Varoujan Hagopian, PE Civil No. 40230; Date: 3/5/2021 — "WPA Form 3A-Notice of Intent for an Ecological Restoration Project"; Prepared by: Bradford Saunders, GEI Consultants, Inc.; Prepared for: Town of Lexington, Department of Engineering; Date: 3/5/2021 — Attachment C: Flex MSE Vegetated Wall System — Memorandum: From: Brooke Monroe, Pinebrook Consulting, To: Ryan J. Paul and Eric Kelley, Environmental Partners; RE: Wetland Evaluation/Delineation for Oxbow/Constitution Road Drainage Improvement Project, Lexington, Massachusetts"; Date: 4/11/2019 — Memorandum: From: Eric Kelley, PE, Environmental Partners, To: Lexington Conservation Division; RE: Notification of Filing Ecological Restoration Notice of Intent, Kiln Brook Stream Daylighting—Lexington, MA; Date: 2/16/2021 — Project Narrative: Kiln Brook Daylighting—Lexington, MA; uploaded 3/8/2021 Mr. Matthew Weisman, Lexington Engineering and Mr. Eric A. Kelley, Environmental Partners Group, presented before the Commission. Mr. Varoujan Hagopian, GEI Consultants, also assisted in answering questions from the Commission. Questions from the Commission: — What is the riprap material made of? — Does the vegetated wall system function even if no vegetation is established? — What is the reason for the fence? — How critical is the design of the bottom of the wall and is there a risk of the wall getting undercut due to high velocities? Response from the Representatives: — The rip rap is composed of a layer of stone underlain by synthetic fabric. The reason for using synthetic fabric is because in a heavy storm, the flow velocity in the channel will be very fast and once it exceeds 5-6 feet per second, the synthetic material is needed to avoid erosion. It is also a UV stabilized material that should last for over 40 years without falling apart and will look more natural once stabilized in the future. — The wall will be robust even without vegetation, however, the vegetation is for aesthetics. Vegetation is not critical to the long term outcome of the wall. — The fence will be installed as security for the homeowner and will be roughly 4-6 feet tall on the center. The PVC piping should not affect the tie back system and the wall and fence will be constructed simultaneously to avoid the grid becoming torn or distressed. — The filter fabric comes underneath the wall similar to the flashing on a building. 6