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The MetroWest Water Supply Tunnel
Massachusetts Water Resources Authority

Tunnel workers, a.k.a.
Sandhogs (tunnel workers) in front of their Tunnel Boring Machine (TBM) after the MWWST holethrough

MWRA turned on the MetroWest Water Supply Tunnel in November 2003.

The new tunnel greatly enhances the security, capacity and reliability of MWRA's entire water transmission system.

Until now, MWRA has relied on a single 1940's-era surface aqueduct, the Hultman Aqueduct, to serve all of Metro Boston. With its leaks and aging valves, the Hultman needed to be taken off-line for major repairs.

Before the MetroWest Tunnel, failure of the Hultman could have caused nearly complete interruption of Boston's water supply. This would have been a disaster for the region's public health, safety and economy.

Facts about the MetroWest Water Supply Tunnel
Purpose: To enhance the security, capacity and reliability of the water system that serves 2.3 million people in 40 communities
Total Program Budget Set in 1995: $728 million
Total Program Estimated Completion Costs: $665 million (includes design, construction management, construction
and other support costs)
Awarded construction: 8 contracts valued at over $506 million in construction costs
Length of tunnel: 17.6 miles – roughly the distance from Rte. 495 to Rte 128, parallel to the Mass.Turnpike

Installing forms for concrete lining 2001-2002

Installing forms for concrete lining 2001-2002

Mined at 16 feet, finished at 14 feet
200-500 feet deep
Years to Complete each phase of construction:
Excavating Shafts: 1 year
Mining: 2 years
Lining: 2 years
Line Shafts: 1 year
Piping, connections and disinfection: 1 year
Construction schedule and duration: Construction work took place over a 7-year period with over 6 million man-hours worked. Work proceeded 24 hours per day on 3 shifts, 5-6 days per week with no fatalities.

3 machines, each valued at over $7 million, were used to mine the tunnel

3 major working shafts: (Southborough,
Framingham and Weston)

9 connections to water facilities and communities

Under five communities:

Marlborough, Southborough, Framingham,
Wayland, and Weston

Wye intersection 235 feet below the Mass. Turnpike tolls at Rte. 128

Average production rate: 57.1 feet per day
Total rock excavated: 1, 025,000 cubic yards
Kinds of Rock Excavated: Granite, gneiss, shist, quartzite and others

Workers inside the tunnel

Workers inside the tunnel

Total Amount of Concrete Used for Lining: 184,722 cubic yards
Concrete Production Rate: 154 cubic yards per day
Average production for lining: 77 lineal feet per day
Project coordinated with: Treatment Facilities at Walnut
Hill (Marlborough) and Covered
Storage at Norumbega
Reservoir (Weston)
450 million gallons per day
Amount of water needed to fill the tunnels and shafts: 105.5 million gallons
Disinfected with: 42,000 gallons of sodium
hypochlorite (chlorine)
Total Number of People Who Worked on the Project: 1,907
Maximum Number of People Working at One Time: 598
Unions on the Job: Tunnel Workers Local 88, Operators Local 4, Electricians Locals 103 and 96

Broke Ground late 1996

Finished construction on schedule in Spring 2003

Final Testing and Disinfection in Summer/early Fall 2003

Memorandums of Agreement with Communities: Weston
Designers: Sverdrup/Jacobs Civil Inc.
Construction Management Team: Stone and Webster Massachusetts Inc., a Shaw Group Co.
Parsons Brinckerhoff Construction Services Inc.
Regina Villa Associates
Hager GeoScience
H2O Engineering Consulting Assoc.
DMC Engineering
Judith Nitsch Engineering
Revet Environmental
Major Contractors: Shea/Traylor/Healy
Modern Continental/Obayashi
Barletta Heavy Division

Contact Us

If you have questions or concerns about this project, please e-mail Len Cawley, MWRA Community Relations Manager or call (617) 660-7972.

Further Reading

MWRA's Integrated Water Quality Supply Program

John J. Carroll Water Treatment Plant

Annual Water Quality Test Results

MWRA Water System


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Created 2013

Updated August 23, 2022

Historic Withdrawls Reservoir Levels