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The MetroWest Water Supply Tunnel

HOLE-THROUGH | Quicktime Video
Completing excavation phase of the 17.6-mile tunnel in Oct 2000.

 More Information
"Hole-Through" Video from Oct 27th Milestone
Project Alignment Map

WRA is making final preparations to turn on the MetroWest Water Supply Tunnel, a critical project for water transmission redundancy that was put on hold more than 50 years ago.

The new water tunnel is on schedule to to go on line at the end of October, 2003. It will greatly improve water transmission reliability and redundancy.

The MetroWest Water Supply Tunnel (MWWST) will increase the water delivery system's overall capacity by 450 million gallons per day. It will also link MWRA's reservoirs, water treatment, and storage facilities to the City Tunnel and local distribution pipes and to the people that they serve.


Planning for the MetroWest Water Supply Tunnel began in 1988. November 1996 marked the beginning of construction.

The 17.6- mile tunnel was bored through solid bedrock 200 to 500 feet below the communities of Southborough, Marlborough, Framingham, Wayland and Weston. The tunnel was excavated by modern tunnel boring machine (TBM) technology.

Direction of Mining
From east to west. Two directions, both east and west from Shaft L, Framingham. The Middle and Western Tunnel Segments now join at Shaft E. From east to west, then curving north.
Endpoint East
Shaft E, Southborough, where it joins the Middle Tunnel Segment. The Wye, Weston, where it joins the Eastern Tunnel Segment. A wye is an underground with no surface connections. Shaft 5A, Weston, the eastern terminus of the tunnel.
Endpoint West
Shaft D, Marlborough, the western terminus of the tunnel. Shaft E, Southborough, where it joins the Western Tunnel Segment. Shaft W; Weston.
Communities Traversed
From Southborough to Marlborough. The east heading extends under Framingham through Wayland to Weston. The west heading extends under Framingham into Southborough. Weston.
Surface Connections
Shaft D will connect the MetroWest Water Supply Tunnel to the new Walnut Hill Water Treatment Plant. The tunnel will carry water treated at the plant to service communities. Shaft N West connects the MetroWest Water Supply Tunnel to the Norumbega Covered Storage Facility. Shaft N East will carry water from the facility back to the MetroWest Water Supply Tunnel, continuing water transmission to metropolitan Boston. Shaft 5A connects the MetroWest Water Supply Tunnel to the City Tunnel. Shaft W connects the tunnel to covered storage facilities at Loring Road, Weston.
Segment length
4.9 miles 11.9 miles .8 miles

Over 6 years, approximately 1.4 million cubic yards of rock (or "muck") will be excavated from the tunnel:
850,000 cubic yards removed from Shaft L in Framingham
680,000 cubic yards used as backfill for the Shaft L worksite
170,000 cubic yards remaining processed and sold by New England Sand and Gravel Company
Rock from the other shafts sold as clean backfill and aggregate.


A tunnel hotline has been established for the convenience of residents who may be affected. Questions, concerns or complaints on the project can be directed to:

1-888 TUNNEL2 (or 886-6352)

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