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Documentation Submitted: — "MIT-LL 4th Feeder Infrastructure Upgrade Project: Environmental Resources Map" map set; Sheet 1, 2, 3, 4 of 4; Prepared for: Eversource Energy; Prepared by: SWCA Environmental Consultants; dated December 11, 2020 — "Notice of Intent: MIT Lincoln Laboratory Infrastructure Improvement Project" and attachments; Prepared for: Eversource Energy; Prepared by: SWCA Environmental Consultants; dated December 2020 o Description of Project; "Eversource MIT Lincoln Laboratory Infrastructure Upgrade Project"; dated December 15, 2020 o "WPA Form 3 —Notice of Intent" application; dated December 14, 2020 o Notice of Intent Narrative; dated December 2020 o Figure 1: USGS Topographic Figure o Figure 2: Ortho Imagery Figure o "StreamStats Report - Stream SA"; dated December 15, 2020 o "Horizontal Directional Drill Contingency Plan" — "Stormwater Management Report" Technical Memorandum; Prepared for: Lexington Conservation Commission; Prepared by: Rebecca Weissman, Natural Resources Team Lead, SWCA; dated December 15, 2020 Ms. Becky Weissman, SWCA Environmental, and James Clancy, Eversource, presented the project to the Commission. Eversource is proposing to provide additional electrical supply from the existing substation on Hartwell Avenue to the MIT Lincoln Laboratories. The conduit will be installed by a variety of methods. From the entrance driveway to beyond the Minuteman bike path, 665 linear feet will be installed by Horizontal Directional Drill (HDD), a trenchless method used to avoid impacting certain environmental resources. Also, from this point to an existing manhole, 878 linear feet will be installed by conventional open trenching. The majority of this project is within existing roadway; however, a small portion connects to a manhole that is just off the roadway, but still within the road layout. Eversource is using two manholes, one on Wood Street and another located at the intersection with Maguire Road. Questions from the Commission: — Why take such a turn northward on Hartwell Avenue, to go right back southward? — Are the drilling muds constrained within the entry/exit area as shown? — Does the contingency plan include issues related to fuel spills? — Will the excess material be hauled away? — Are we concerned about wetlands west of Wood Street? Responses from the Applicant: — There are existing manholes on Hartwell Avenue that Eversource will need to connect conduits to. — Will discuss with the engineers and provide an answer at a later date. — Yes, the HDD contingency plan says they will keep mud storage tanks on site. — Typically Eversource will haul it off immediately to an appropriate location, however will ask the Engineers. — Did not identify wetlands close to Wood Street. The proposed work ends just off of Wood Street, and any wetlands appear to be over 100 feet away.