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MWRA outlines Needham dewatering drain line: 36‑inch pipe, staging and 2027 construction target
Summary
MWRA told the Select Board it needs a 1,250‑foot, 36‑inch dewatering drain line from the I‑95 Highland cloverleaf to the Charles River as early enabling work for the South Tunnel; construction is targeted for 2027 with possible night work in commercial areas and replacement of about 300 linear feet of older town sewer pipe.
MWRA tunnel program staff presented an early enabling project for the South Tunnel: the Needham dewatering drain line, a roughly 1,250‑linear‑foot, 36‑inch pipeline that will carry treated construction and groundwater from the Highland Ave/I‑95 cloverleaf tunnel shaft to an outfall on the Charles River.
"It's a piece of construction we need to do ahead of the large tunnel construction contract," MWRA acting tunnel director Paul Savard said, explaining the line will permit the contractor to manage and discharge infiltration and commissioning water when the South Tunnel construction begins. Design manager David Afton outlined the alignment: a trenchless crossing (about 150 feet) under the I‑95 ramp, then cut‑and‑cover construction along Brook Road, Arlington Road and Charles Street, and a private‑property section through 163 Highland Ave to the riverbank for the outfall.
Afton said the project includes about 850 feet of cut‑and‑cover in public rights‑of‑way and a 250‑foot private‑property cofferdam/outfall work area at 163 Highland Ave; it will also require removal and replacement of roughly 300 linear feet of a brittle vitrified clay town sewer main near the Charles River bank. MWRA anticipates bidding this fall, onboarding a contractor late fall/early winter and starting construction in spring 2027 with substantial completion by spring 2028, recognizing a Needham winter street moratorium.
Board members asked about noise, traffic, sewer bypassing during sewer work and the scale of flows expected for tunnel dewatering. MWRA staff said construction is typical pipeline work with deep trenches (10–15 feet), night work could reduce daytime commercial impacts and that inflow mitigation techniques would be used during tunnel operations; MWRA cited a target permitting rate of up to 5,000,000 gallons per day for tunnel dewatering (subject to DEP/NPDES permitting and mitigation during operations).
Why it matters: the drain line is critical early work to enable MWRA’s South Tunnel construction (targeted to begin in 2028). It will produce localized construction impacts to streets and require coordination with DPW, police and property owners for temporary easements and traffic management.
