Table of Contents
Introduction
Overview
Through the Metropolitan Water Tunnel Program (Tunnel Program), MWRA will construct two new water supply tunnels that will provide redundancy for MWRA's existing Metropolitan Tunnel System, which includes the City Tunnel (1950), City Tunnel Extension (1963) and Dorchester Tunnel (1976). The Tunnel Program will also allow our aging existing water tunnel system to be rehabilitated without interrupting service. The Tunnel Program is in the preliminary design and environmental review stage. Final design will begin after preliminary design is complete, with tunnel construction planned to occur from approximately 2027 through 2040.
Background
MWRA provides wholesale water and wastewater services to over 3.1 million customers in 61 communities in eastern and central Massachusetts with most service communities located in the Greater Boston area. The Quabbin Reservoir and Wachusett Reservoirs, which are the main water supply sources, are located 65 and 35 miles west of Boston, respectively. Water from the reservoirs is treated in the John J. Carroll Water Treatment Plant before transmitting to the Greater Boston area through a number of existing tunnels and aqueducts.
A redundant water transmission system exists for approximately 25 miles from the Wachusett Reservoir to the beginning of the existing Metropolitan Tunnel System.
The existing Metropolitan Tunnel System carries approximately 60% of the Metropolitan Boston area's daily demand through the remaining 19 miles of tunnels. With no redundancy to the Metropolitan Tunnel System, partial system shutdowns for planned maintenance of the aged infrastructure or unplanned emergencies cannot take place.
The planned Tunnel Program will provide redundancy for this crucial part of our water infrastructure.
Why Redundancy?
Redundancy in the water supply infrastructure for the reliability of service and operational maintenance has been part of the plan since as early as 1937. Various versions of tunnel loops and redundant tunnels have been proposed over the years.
A significant portion of these plans have been implemented. With the completion of the MetroWest Water Supply Tunnel in 2003, the water transmission system has redundancy from the John J. Carroll Water Treatment Plant to the beginning of the existing Metropolitan Tunnel System.
The Metropolitan Tunnel System was constructed in the 1950s to the 1970s and has been in continuous service ever since. While the concrete-lined deep rock tunnels have a long design life, some of the associated valves and piping are in poor condition after over 50 years. In order to exercise, service and replace some of these valves and piping without interruption to water supply, a redundant system is required.
Program Goals
The Tunnel Program was conceived to address several outstanding challenges, most notably the fact that the existing Metropolitan Tunnel System cannot be maintained or repaired nor can an emergency be readily addressed because shut down of the system is not currently possible without imposing a boil-water order.
The first and foremost goal of the Program is an operational goal; to protect public health, provide sanitation, and provide fire protection. The MWRA exists to provide these services. In support of this overall goal, the Program is intended to:
- Provide full redundancy for the Metropolitan Tunnel System:
- Provide normal water service and fire protection when the existing tunnel system is out of service
- Provide the ability to perform maintenance on existing tunnels year-round
- Provide uninterrupted service in the event of an emergency shut down
- Meet high day demand flow with no seasonal restrictions
- Avoid activation of emergency reservoirs
- Meet customer expectations for excellent water quality
- Preserve sustainable and predictable rates at the water utility level
- Minimize cost of borrowing
- Be constructible
- Result in no future boil water orders
The selected tunnel alternative is expected to meet all of these goals.
About the Program
The proposed Metropolitan Water Tunnel Program will consist of approximately 15 miles of deep rock tunnels and surface connections to provide redundancy to the existing Metropolitan Tunnel System in the Metropolitan Boston area.
As proposed, the new tunnel system will consist of a northern tunnel and a southern tunnel in and around the Metropolitan Boston area. Both tunnels are proposed to begin near the terminus of the Hultman Aqueduct and MetroWest Water Supply Tunnel in the town of Weston, Massachusetts. The northern tunnel is proposed to extend north with a connection to the MWRA water system in the vicinity of Waverly Oaks Road near the Belmont/Waltham line. The southern tunnel is also proposed to extend south with a connection to the MWRA water system in the Morton Street area near the American Legion Highway in Boston. The proposed tunnels will have intermediate connection points to other existing MWRA facilities along the alignment.
After the May 2010 water main break and during the mid-2010s, it became apparent that MWRA would need to execute another large water tunnel program in the near future to provide redundancy for maintenance and emergencies. On October 6, 2016, the MWRA Board of Directors held a special meeting where MWRA staff provided a briefing on the status of the existing MWRA water transmission system and the lack of redundancy for the Metropolitan Tunnel System. The preferred alternative of constructing two tunnels, one to the north and one to the south, was recommended.
At the conclusion of the special meeting, staff were directed to brief member communities and state and local officials on the Metropolitan Tunnel Redundancy initiative in order to build consensus and support for the preferred project approach. On December 8, 2016, a Long-Term Water Redundancy Forum hosted by the MWRA Advisory Board for the customer communities was held at Boston College. MWRA staff presented the history of the MWRA waterworks system, the need for Metropolitan Tunnel Redundancy and the challenges, both implementation and financial, of building redundancy.
On January 19, 2017, the MWRA Advisory Board met and voted to support moving forward with a deep rock, two-tunnel project. They also voted also to recommend: a program management division approach to manage the Program similarly to the model used for the Boston Harbor Project (BHP); concurrent construction of both tunnels rather than a phased approach; and allocation of any revenue from non-typical or one-time water users (e.g. emergency drought connections) towards the cost of the program.
On February 15, 2017, the MWRA Board of Directors approved the preferred alternative of construction of northern and southern deep rock tunnels to provide redundancy for the Metropolitan Tunnel System, and directed staff to proceed with preliminary design, geotechnical investigations and Massachusetts Environmental Policy Act (MEPA) review of the Program.
On October 17, 2022, MWRA filed its Draft Environmental Impacts Report (DEIR) for the Metropolitan Water Tunnel Program. The DEIR responds to the Secretary of EEA’s Environmental Notification Form (ENF) Certificate issued on May 7, 2021 and provides responses to all comments received on the ENF.
On December 16, 2022, the EEA issued its Certificate of the Secretary of Energy and Environmental Affairs on the DEIR for the Metropolitan Water Tunnel Program.
On July 31, 2023, MWRA submitted the Supplemental Draft Environmental Impact Report (SDEIR) [Vol. 1 | Vol. 2] for the Tunnel Program which provides responses to the EEA Secretary's DEIR Certificate.
On September 29, 2023, the EEA issued its Certificate of the Secretary of Energy and Environmental Affairs on the SDEIR.
On February 15, 2024, MWRA submitted its Final Environmental Impact Report (FEIR) for the Tunnel Program. The FEIR responds to the EEA Secretary's SDEIR Certificate.
On April 1, 2024, the EEA issued its Certificate of the Secretary of Energy and Environmental Affairs on the Final Environmental Impact Report (FEIR).
Given the significant community impacts and difficulties associated with large diameter surface piping, together with operational reliability concerns, MWRA staff are pursuing a preferred all-tunnel redundancy alternative. The alignment, which was subject to a detailed review and alternatives analysis during the Massachusetts Environmental Policy Act (MEPA) public review period, is shown below.
This alternative consists of two deep rock tunnels, both beginning in Weston near the Massachusetts Turnpike/Route 128 interchange where they will connect to the existing water system. The Northern Tunnel generally follows the route of MWRA’s existing Weston Aqueduct Supply Main (WASM) 3 transmission main near the Waltham/Belmont line. The length of the Northern Tunnel would be approximately 4.8 miles and the tunnel would have a finished inside diameter of approximately 10 to 12 feet.
The Southern Tunnel would run east to southeast to tie into the MWRA water system in the Morton Street area near the American Legion Highway in Boston. The length of the Southern Tunnel is anticipated to be approximately 10 miles and would have a finished inside diameter of 10 to 12 feet. Both the normal Northern and Southern Tunnels are anticipated to include intermediate connection shafts to existing water system infrastructure.
The proposed plan limits community disruptions and construction impacts to the locations of the tunnel construction and connection shaft sites. The all-tunnel alternative meets the strategic objective of being able to make a seamless transition to a backup supply, allowing maintenance to be scheduled for the Metropolitan Tunnels, without use of a boil water order, without impacting local fire protection abilities, and without noticeable changes in customers’ water quality, flow or pressure. It has the ability to meet high water system demand conditions, which extends the potential time frame for future maintenance and rehabilitation activities.
The final cost of the Tunnel Program is not yet defined because final design and construction are still years away with much work to do in the meantime. However, an estimated $2.1 billion is being carried in our Capital Improvement Program Budget (Proposed FY25). The impacts of the estimated cost are included in MWRA’s current rate projections.
The Tunnel Program is currently in the design stage. The next few years will include Program wide activities including detailed design, continued field investigations, construction management, and preparation of construction contract document, land acquisition, TBM power supply, and stakeholder outreach.
A snap shot of upcoming Tunnel Program activities includes:
- A Final Design Engineering consultant will be contracted in late 2024 to begin detailed design of both the North and South Tunnel systems. Field investigations at future shaft sites and along the tunnel alignment will continue during final design. The Final Designer will serve as the engineer-of-record for the Tunnel Program and will be involved throughout construction. The Final Designer will work closely with MWRA’s Tunnel Redundancy Department through all phases of final design which is expected to take about 5 years.
- Procurement for a Construction Management consultant will begin in 2025 with selection occurring in 2026. The Construction Manager will be responsible for construction management and resident inspection services for all construction and construction support activities during the pre-construction, construction and start-up phases of all Construction Contracts for the Tunnel Program. The Construction Manager will work closely with MWRA’s Tunnel Redundancy Department, have expertise in deep hard rock tunnel construction, and managing complex megaprojects (i.e., projects over $1B).
- Procurement for construction of the South Tunnel is targeted to begin in 2027 with actual construction starting in 2028. Procurement for construction of the North Tunnel is targeted to begin in 2028 with actual construction starting in 2029. Tunnel construction, including surface work and commissioning, is estimated to take 8 to 12 years to complete. Construction of the new tunnels is planned to be completed and the tunnels in operation by 2040.
- It is expected that two or three smaller construction contracts will be procured and completed prior to the start of tunnel construction to remove early enabling works from the tunnel contracts’ critical paths. These enabling contracts are related to demolition of existing buildings, site reconfiguration to allow continuity of current use, and dewatering drain line work at or near future launching shaft sites.
- Prior to construction the MWRA will acquire land at shaft sites and easements along the tunnel and in roadways or on public land for new water and drain pipelines.
- Subterranean easements will be acquired for each property below which the new tunnels will be constructed. The subterranean easements will be 200 to 450 feet below ground and will not allow for surface access, and thus will not affect property usage above the tunnel. Currently, it is estimated that approximately 600 subterranean easements will be required.
- The MWRA is working with Eversource to ensure that sufficient power supply is available at the launching shaft sites prior to the start of tunnel construction. When the Tunnel Program is complete, the added power supply will remain and provide further resilience to the power grid.
- Community and stakeholder outreach has been ongoing since the early stages of the Tunnel Program. Over 140 meetings with various community representatives, state agencies, stakeholders, and property owners have occurred. Starting in late 2024, broader public information sessions will be held with a variety of topics including a Tunnel Program overview, an overview of tunneling methods (i.e. “Tunneling 101”) and associated construction period impacts such as traffic, noise and vibration, and other topics of interest to stakeholders. Outreach to stakeholders will be in alignment with MWRA’s overall environmental justice strategy and will continue through final design and construction.
For more information on ongoing and future activities for the Metropolitan Water Tunnel Program, see the MWRA Board of Directors March 13, 2024 meeting materials.
Community Updates
Through the Metropolitan Water Tunnel Program (MWTP), MWRA will construct two new water supply tunnels that will provide redundancy for MWRA's existing Metropolitan Tunnel System, and allow our aging existing water tunnel system to be rehabilitated without interrupting service.
Schedule
Final design started 2024 with a target for the first tunnel construction contract bidding in 2027.
Work in Host Communities
The MWTP is planned to be constructed in seven communities: Boston, Brookline, Needham, Newton, Waltham, Weston and Wellesley. To support the tunnel design, MWRA is performing geotechnical investigation field work consisting of test borings and various types of surface geophysical testing to better understand the subsurface conditions that are likely to be encountered during construction. Depending on the location, this work may be seen along city streets and can have impacts on neighborhoods. MWRA’s Community Relations Department works with municipal staff and residents to ensure good communications during these projects.
Notices for Abutters in Boston
Notices are distributed to those abutting work to notify them of work in their area.
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| There are no active notices at this time. |
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01/10/2025: MWRA Announces First Metropolitan Water Tunnel Program Public Information Session on February 5, 2025 in Needham - More information here 03/07/2024: Field work within Forest Hills Cemetery property (Jamaica Plain) 01/24/2024: Field work in Boston (Jamaica Plain) within the Daughters of St. Paul property 01/10/2024: Field work n Boston (Jamaica Plain): within the Italian Home for Children property off Centre Street 11/21/2023: Field work within the Arnold Arboretum at Meadow Road and Bussey Hill Road 10/03/2023: Field work in the grassy area behind the parking lot for the Department of Public Health (Jamaica Plain) 07/21/2022: Field Work on Woodlawn Street 08/19/2021: Field Work at City of Boston Department of Public Works Lot near 415 American Legion Highway 06/24/2021- Field Work in 430 and 500 Canterbury Street area |
Meetings in Boston
04/04/2023 - Jamaica Plain Neighborhood Council (JPNC)
Presentation
02/28/23 - Asticou Martinwood South St. Neighborhood Association
Presentation
Geotechnical Work in Boston
The Metropolitan Water Tunnel Program is working on the geotechnical investigation at specific locations in your community. The following fact sheet explains geotechnical investigation work.
Notices for Abutters in Brookline
Notices are distributed to those abutting work to notify them of work in their area.
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| 06/16/2025: Survey in Brookline starting on June 16, 2025 – As part of the MWTP, MWRA and its final design consultant will conduct field survey within the Town of Brookline starting on Monday, June 16. The survey activities will include a two-person crew using conventional land surveying equipment. Survey will be conducted in the vicinity of the MWRA’s Newton Street Pumping Station. The survey is anticipated to take approximately two weeks. Please contact Carmine DeMaria, MWRA Community Relations Coordinator or Tunnels.Info@mwra.com if you have any questions about the MWTP. |
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1/10/2025: MWRA Announces First Metropolitan Water Tunnel Program Public Information Session on February 5, 2025 in Needham - More information here 12/12/2024: Field work on the Robert T. Lynch Municipal Golf Course 02/16/2024: Field work on Town of Brookline property along the shoulder of Transfer Station Drive 08/15/2023: Field work within within Transfer Station Drive area 05/30/2023: Field work in Allandale Farm area at 186 to 282 Newton Street 07/21/2022: Field work in Fairgreen Place area 05/12/2022: Field work at Wolcott Road and Shaw Road area 05/12/2022: Field work at Robert T. Lynch Municipal Golf Course, along the cart path of the 18th hole 07/08/2021: Field work at Newton Street Pump Station at 321 Newton Street |
Meetings in Brookline
Information about public meetings in your town will be posted here.
Geotechnical Work in Brookline
The Metropolitan Water Tunnel Program is working on the geotechnical investigation at specific locations in your community. The following fact sheet explains geotechnical investigation work.
Test Boring Water Readings for Needham
As part of the MWTP, the MWRA and its consultants plan to continue collecting monthly water readings from sensors installed in their exploratory test borings completed within the Town of Needham.
Notices for Abutters in Needham
Notices are distributed to those abutting work to notify them of work in their area.
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9/19/2025: Field work at 208 Highland Ave., Needham 7/30/2025: Field work at the intersection of Crawford Street and Kearney Street, Needham |
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6/30/2025: Field work at Mills Field, 96 Gould Street in Needham 06/25/2025: Survey in Needham Starting on June 25, 2025 – As part of the MWTP, MWRA and its final design consultant will conduct field survey within the Town of Needham starting on Wednesday, June 25. The survey activities include a two-person crew using conventional land surveying equipment. Survey will be conducted along St. Mary’s Street. The survey is anticipated to take approximately two days. Please contact Carmine DeMaria, MWRA Community Relations Coordinator or Tunnels.Info@mwra.com if you have any questions about the MWTP. 6/16/2025: Field work within the Riverside Park in Needham 6/12/2025: Site Visit in Needham during week of June 16, 2025 - As part of the MWTP, MWRA and its final design consultant will visit a Program shaft site within the Town of Needham on Tuesday, June 17. The site is in the vicinity of the MWRA Sudbury Aqueduct on St Mary Street. Please contact Carmine DeMaria, MWRA Community Relations Coordinator, or Tunnels.Info@mwra.com if you have any questions about the MWTP. 5/27/2025: Survey in Needham starting on May 27, 2025 – As part of the MWTP, MWRA and its final design consultant will conduct field survey within the Town of Needham starting on Tuesday, May 27. The survey activities will include a two-person crew using conventional land surveying equipment. Survey will be conducted in the vicinity of Highland Avenue and I-95. The survey is anticipated to take approximately two weeks. Please contact Carmine DeMaria, MWRA Community Relations Coordinator or Tunnels.Info@mwra.com if you have any questions about the MWTP. 5/14/2025: Survey in Needham starting on May 14, 2025 – As part of the MWTP, MWRA and its final design consultant will conduct field survey within the Town of Needham starting on Wednesday, May 14. The survey activities will include a two-person crew using conventional land surveying equipment. Survey will be conducted along St. Mary’s Street. The survey is anticipated to take approximately two weeks. Please contact Carmine DeMaria, MWRA Community Relations Coordinator or Tunnels.Info@mwra.com if you have any questions about the MWTP. 3/28/2025: Survey in Needham Starting on March 31, 2025 – As part of the MWTP, MWRA and its final design consultant will conduct field survey within the Town of Needham starting on Monday, March 31. The survey activities will include a two-person crew using conventional land surveying equipment. Survey will be conducted along Brook Road, Wexford Street, Fremont Street, Arlington Road, and Charles Street. The survey is anticipated to take approximately two weeks. Please contact Carmine DeMaria, MWRA Community Relations Coordinator, or Tunnels.Info@mwra.com if you have any questions about the MWTP. 3/10/2025: Site Visits in Needham on March 12, 2025 - As part of the MWTP, MWRA and its final design consultant will visit the Program’s shaft sites within the Town of Needham on Wednesday, March 12. The two sites are in the vicinity of Highland Ave and I-95 and the MWRA Sudbury Aqueduct on St Mary Street. Please contact Carmine DeMaria, MWRA Community Relations Coordinator, or Tunnels.Info@mwra.com if you have any questions about the MWTP. 01/10/2025: MWRA Announces First Metropolitan Water Tunnel Program Public Information Session on February 5, 2025 in Needham - More information here 7/15/2024: Field work at the traffic island off Highland Circle 5/10/2024: Field work on the MassDOT property within the northeast cloverleaf of I-95 and Highland Avenue, and one shallow boring off Brook Road in Needham12/13/2023: Field work in the parking area nearby the basketball court at the Needham Housing Authority at 28 Captain Robert Hook Drive 9/12/2023: Field work, at the back of a parking lot on Cabot Street 7/05/2022: Field Work, Northwest cloverleaf of the intersection of I-95 and Highland Avenue 5/03/2022: Field Work, Wellesley Avenue and the Sudbury Aqueduct trail near Cedar Street 6/24/2021: Field Work, Walking trail in the Upper Charles River Reservation east/southeast of Highland Avenue 6/07/2021: Field Work, 31 St. Mary Street 5/06/2021: Field Work, Evergreen Road and the Sudbury Aqueduct trail near St. Mary Street |
Meetings in Needham
The Metropolitan Water Tunnel Program has held the following public meetings in your town.
Public Information Session at Needham Town Hall on 02/05/2025
Presentation
Needham Select Board on 01/28/2025
Presentation
Needham Select Board on 11/22/2022
Presentation
Geotechnical Work in Needham
The Metropolitan Water Tunnel Program is working on the geotechnical investigation at specific locations in your community. The following fact sheet explains geotechnical investigation work.
Notices for Abutters in Newton
Notices are distributed to those abutting work to notify them of work in their area.
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9/11/2025: Field work at the intersection of Rolling Lane and High Rock Terrace, Newton 8/28/2025: Field work within the City of Newton right-of-way on Deborah Road, Newton |
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6/30/2025: Field work at the traffic island between Grove Street and Moulton Street in Newton 1/10/2025: MWRA Announces First Metropolitan Water Tunnel Program Public Information Session on February 5, 2025 in Needham - More information here 8/02/2024: Field work at the intersection of Donna Road and Nardell Road 1/08/2024: Field work on the DCR Leo J Martin Memorial Golf Course property in Newton 8/02/2023: Test boring work at Hartman Park - Update 7/06/2023:Field work in Newton Lower Falls, Hamilton field area 8/11/2022: Field work at Countryside Road, within the former water tower parcel 5/20/2022: Field work at Leo J. Martin Memorial Golf Course near the 16th hole and Pine Grove Avenue 4/28/2022: Field work along the south side of Dedham Street 4/28/2022: Field work in Baldpate Hill Road area |
Meetings in Newton
Information about public meetings in your town will be posted here.
Geotechnical Work in Newton
The Metropolitan Water Tunnel Program is working on the geotechnical investigation at specific locations in your community. The following fact sheet explains geotechnical investigation work.
Notices for Abutters in Waltham
Notices are distributed to those abutting work to notify them of work in their area.
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9/4/2025: Field work at 216 Felton Street, Waltham 8/15/2025: Field work at 95 Sawyer Road, Waltham |
Meetings in Waltham
The Metropolitan Water Tunnel Program has held the following public meetings in your city.
Waltham City Council on 06/21/2021
Presentation | Minutes
Geotechnical Work in Waltham
The Metropolitan Water Tunnel Program is working on the geotechnical investigation at specific locations in your community. The following fact sheet explains geotechnical investigation work.
Notices for Abutters in Wellesley
Notices are distributed to those abutting work to notify them of work in their area.
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7/23/25: Field work at 112 Worcester St., Wellesley 7/18/25: Field work at 56 Cedar St., Wellesley6/13/25: Field work at 130-136 Worcester St., Wellesley 1/10/2025: MWRA Announces First Metropolitan Water Tunnel Program Public Information Session on February 5, 2025 in Needham - More information here 05/07/2024: Field work within the the Hegarty Pump Station property on Barton Road, Wellesley 7/20/2023: Field work within the Wellesley Housing Authority’s Barton Road property 07/13/2023: Field work along the access road to the Schofield Elementary School at 27 Cedar Street 06/14/2022: Field work, 100 Walnut Street, near the intersection of Walnut Street and Cedar Street 05/19/2022: Field work, Redwing Road area 08/19/2021: Field work at 125 Barton Road, within the Hegarty Street Pump Station site |
Meetings in Wellesley
03/21/2023 - Wellesley School Committee
Presentation | Meeting Documents
11/15/2022 - Wellesley Board of Public Works
Presentation | Video
Geotechnical Work in Wellesley
The Metropolitan Water Tunnel Program is working on the geotechnical investigation at specific locations in your community. The following fact sheet explains geotechnical investigation work.
Notices for Abutters in Weston
Notices are distributed to those abutting work to notify them of work in their area.
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1/10/2025: MWRA Announces First Metropolitan Water Tunnel Program Public Information Session on February 5, 2025 in Needham - More information here 11/09/2023: Field work on DCR Leo J Martin Memorial Golf Course property 10/23/2023: Field work on MWRA property off Loring Road 09/12/2023: Field work on the grass shoulder of the ramp from I-95 southbound to I-90 west-bound 08/11/2023: Test boring at the intersection of Rt 30 and River Road 01/20/2023: Field work on Park Road in Weston between I-90 and Route 30 08/18/2022: Field work on River Road/South Street between Norumbega Road in Weston to Charlesbank Way in Waltham 07/28/2022: Field work along Norumbega Road from 99 Norumbega Road to the intersection with River Road 07/08/2022: Field work on Norumbega Road from 99 Norumbega Road to the intersection with River Road 06/02/2022: Field work at Leo J. Martin Memorial Golf Course area, at 190 Park Road, Weston 07/29/2021: Field work near Norumbega Tower Park on Norumbega Road |
Meetings in Weston
Weston Select Board on 01/10/2023
Agenda | Presentation | Minutes | Video
Geotechnical Work in Weston
The Metropolitan Water Tunnel Program is working on the geotechnical investigation at specific locations in your community. The following fact sheet explains geotechnical investigation work.
MWRA's water comes from the Quabbin Reservoir, about 65 miles west of Boston, and the Wachusett Reservoir, about 35 miles west of Boston. The reservoirs are filled naturally. Rain and snow fall onto watersheds (protected land around reservoirs) and eventually turn into streams that flow into reservoirs. This water comes into contact with soil, rock, plants and other material as it follows its path. This process helps to clean the water.
MWRA provides water to 2.5 million people in 53 Massachusetts communities.
The MWRA supplies approximately 200 million gallons of water per day, on average.
MWRA's Quabbin reservoir has 412 billion gallon in capacity and the Wachusett reservoir has 65 billion gallon in capacity. The Quabbin reservoir alone can hold a five-year supply of water. The Quabbin/Wachusett system is so large that it can withstand short- and medium-length droughts and dry periods without a significant impact on its operating levels.
In total, MWRA's water storage tanks hold approximately 180 million gallons of treated water. The water is continuously used and replenished.
The existing MWRA water transmission system has about 105 miles of active tunnels and aqueducts (mostly 10 to 14 feet in diameter) and 39 miles of standby aqueducts. The transmission system is connected to the distribution mains and many smaller community pipes. Visit our water system web pages for more information.
MWRA's drinking water is treated according to strict state and federal standards so that it is safe to drink. Because drinking water is a natural resource, its taste, color and odor can sometimes vary slightly from day to day, from town to town, and from faucet to faucet. MWRA provides drinking water to 51 communities. Some communities are only partially-supplied by MWRA. More detailed information about where the water in your city or town comes from and how it is treated is available in our Annual Water Quality Report.
MWRA tests over 1,600 water samples per month, from our reservoirs all the way to household taps. Water is tested for over 120 possible contaminants.
Yes! MWRA's water is known for its award-winning good taste, year after year. The Massachusetts Water Resources Authority took home the 2023 “People's Choice” award for drinking water in a contest held at the New England Water Works Association’s annual conference in Burlington, Vermont. Samples from competing New England water utilities were tasted at room temperature by an impartial panel of judges and scored on a 1-10 scale.
MWRA has won "New England's Best" three times in the regional contest previously, and was awarded "Best of the Best" nationally by the American Water Works Association in 2021.
Water for most of MWRA's customer communities (except Chicopee, South Hadley Fire District #1 and Wilbraham) is treated at the John J. Carroll Water Treatment Plant at Walnut Hill in Marlborough. Water from the Quabbin and Wachusett reservoirs enters the plant through the Cosgrove or Wachusett Aqueduct. The treated water leaves the plant through the MetroWest Water Supply Tunnel and the Hultman Aqueduct. Water for Chicopee, South Hadley Fire District #1 and Wilbraham is treated at the William A Brutsch Water Treatment Facility in Ware, Massachusetts.
The new tunnel system, as proposed, will consist of a northern tunnel and a southern tunnel in and around the Metropolitan Boston area. Both tunnels are proposed to begin near the terminus of the Hultman Aqueduct and MetroWest Water Supply Tunnel in the town of Weston, Massachusetts. The northern tunnel is proposed to extend north to existing WASM3 transmission main near the Waltham/Belmont line. The southern tunnel would run southeast to tie into the surface connections near Shaft 7C of the Dorchester Tunnel in Mattapan.
The Program alignment study area is shown below:
MWRA has been working closely with the host communities to ensure minimum impact to residents and businesses along the routes.
The Metropolitan Water Tunnel Program recently completed preliminary design and environmental review stage. Preliminary design involved alternatives screening and evaluations, environmental assessment, permitting, base mapping, geotechnical investigation and preliminary design of the new tunnels. Final design will commence after preliminary design is complete, with tunnel construction planned to occur from approximately 2028 through 2040.
The new tunnels are anticipated to be about 10 to 12 feet in finished inside diameter. During construction, the tunnel diameter will be larger to allow for lining of the tunnel and other construction activities.
It is anticipated that the new tunnels will be about 15 miles long in total.
The new tunnels will be constructed deep in bedrock, about 200 to 500 feet below ground surface.
The new tunnels are anticipated to be constructed primarily using Tunnel Boring Machines (TBM). The tunneling mining work will take place deep in bedrock about 200 to 500 deep underground.
Once completed, the tunnel walls will be lined with concrete or steel. The new system will then be cleaned and disinfected before connection to the existing system.
The MWRA has a core mission to provide reliable, cost-effective and high quality water, and a goal of maintaining sustainable and predictable rate assessments to our member communities. In keeping with this, the expected long-term rate impacts resulting from the Tunnel Program have been evaluated.
The final cost of the Tunnel Program is not yet defined because final design and construction are still years away with much work to do in the meantime. However, an estimated $2.1 billion is being carried in our Capital Improvement Program Budget (Proposed FY25). The impacts of the estimated cost are included in MWRA’s current rate projections.
- Certificate of the Secretary of Energy and Environmental Affairs on the Final Environmental Impact Report (FEIR) “MEPA Certificate," EEA Number: 16355, April 1, 2024
- Final Environmental Impact Report (FEIR)
- Final Environmental Impact Report (FEIR) Final Environmental Impact Report (FEIR), (.PDF), February 2024: Preliminary Design, Geotechnical Investigation, and Environmental Impact Report, MWRA Contract 7159. Posted 02/15/2024
- Environmental Justice (EJ) Screening Forms
English | Español | 中文| Kreyòl Ayisyen
Posted 02/06/2024
- Certificate of the Secretary of Energy and Environmental Affairs on the Supplemental Draft Environmental Impact Report (SDEIR) “MEPA Certificate", EEA Number: 16355, September 29, 2023
- Supplemental Draft Environmental Impact Report (SDEIR)
- Supplemental Draft Environmental Impact Report (SDEIR), Volume 1 of 2, July 2023: Preliminary Design, Geotechnical Investigation, and Environmental Impact Report, MWRA Contract 7159, Posted 07/28/2023
- Supplemental Draft Environmental Impact Report (SDEIR), Volume 2 of 2, July 2023: Preliminary Design, Geotechnical Investigation, and Environmental Impact Report, MWRA Contract 7159, Posted 07/28/2023
- Revised Environmental Justice (EJ) Screening Form
English | Español | 中文 | Kreyòl Ayisyen
Posted 07/11/2023
- Draft Environmental Impact Report (DEIR)
- Certificate of the Secretary of Energy and Environmental Affairs on the Draft Environmental Impact Report (“MEPA Certificate”), EEA Number: 16355, December 16, 2022. Posted 12/20/2022
- Draft Environmental Impact Report (DEIR), Volume 1 of 3 October 2022: Preliminary Design, Geotechnical Investigation, and Environmental Impact Report, MWRA Contract 7159, Posted 10/17/2022
- Draft Environmental Impact Report (DEIR), Volume 2 of 3 October 2022: Preliminary Design, Geotechnical Investigation, and Environmental Impact Report, MWRA Contract 7159, Posted 10/17/2022
- Draft Environmental Impact Report (DEIR), Volume 3 of 3 October 2022: Preliminary Design, Geotechnical Investigation, and Environmental Impact Report, MWRA Contract 7159, Posted 10/17/2022
- Environmental Justice (EJ) Screening Forms
English | Español | 中文 | Kreyòl Ayisyen
- Certificate of the Secretary of Energy and Environmental Affairs on The Environmental Notification Form (“MEPA Certificate”), EEA Number: 16355, May 7, 2021. Posted 05/17/2021
- Environmental Notification Form (ENF), March 2021: PRELIMINARY DESIGN, GEOTECHNICAL INVESTIGATION AND ENVIRONMENTAL IMPACT REPORT, MWRA Contract 7159. Posted 03/30/2021
- Fact Sheet, About MWRA's Metropolitan Water Supply Tunnel Program
English | Español | 中文 | Kreyòl Ayisye - Fact Sheet, Shaft Site Selection
English | Español | 中文 | Kreyòl Ayisyen - Fact Sheet, Potential Traffic Impacts
English | Español | 中文 | Kreyòl Ayisyen - Fact Sheet, Potential Noise, Vibration and Air Quality Impacts
English | Español | 中文 | Kreyòl Ayisyen - Fact Sheet, Potential Natural and Cultural Resource Environmental Impacts
English | Español | 中文 | Kreyòl Ayisyen - Fact Sheet, Potential Water Supply Impacts
English | Español | 中文 | Kreyòl Ayisyen - Fact Sheet, About Geotechnical Field Investigation (Field Work)
English | Español | 中文 | Português - Fact Sheet, How Is a Tunnel Constructed?
- Fact Sheet, About MWRA’s Metropolitan Water Tunnel Program Working Group Participation
Meeting Materials and Presentations
- Metropolitan Water Tunnel Program Look Ahead. Meeting materials and presentation, 7/23/2025
- Metropolitan Water Tunnel Program Final Design Engineering Services: WSP USA Inc., Contract 7556 . Meeting materials and presentation, 10/23/2024
- Metropolitan Water Tunnel Program Needs and Overview. Meeting materials and presentation, 03/13/2024
- Metropolitan Redundancy Interim Improvements Projects Update. Meeting materials and presentation, 03/13/2024
- Metropolitan Water Tunnel Program Preliminary Design and Environmental Impact Report. Meeting materials and presentation, 03/13/2024
- Metropolitan Water Tunnel Program Look Ahead. Meeting materials and presentation, 03/13/2024
- FY25 CIP Updated Program Cost Estimate and Cost Controls. Meeting materials and presentation, 3/13/2024
- Contract Structure for Final Design Engineering Services, Contract 7556. Meeting materials and presentation, 03/13/2024
- Metropolitan Water Tunnel Program: Consultant and Contract Structure Update and Tunnel Department Proposed Organizational Changes. Meeting materials and presentation, 12/13/2023
- Metropolitan Water Tunnel Program: Program Support Services, JCK Underground, Inc., Contract 7655, Amendment 2 – First Optional 24-Month Renewal. Meeting materials, 12/13/2023
- Metropolitan Water Tunnel Program Update. Meeting materials and presentation, 05/24/2023
- Metropolitan Water Tunnel Program - Geotechnical Support Services: GEI-McMillen Jacobs JV, Contract 7557. Meeting materials, 12/14/2022
- Metropolitan Water Tunnel Program--Lease for Core Storage Facility: IC Needham Gould Portfolio, LL, W344. Meeting materials, 11/16/2022
- Metropolitan Water Tunnel Program Update. Meeting materials and presentation, 09/14/2022
- Metropolitan Water Tunnel Program Update. Meeting materials and presentation,10/20/2021
- Metropolitan Tunnel Redundancy Program Update: Filing of Environmental Notification Form. Meeting materials, 02/17/2021
- Metropolitan Tunnel Redundancy Program Update. Meeting materials and presentation, 12/16/2020
- Metropolitan Tunnel Redundancy Program Preliminary Design, Geotechnical Investigation and Environmental Impact Report: CDM Smith, Inc. Contract 7159, and Program Update. Meeting materials and presentation, 05/27/2020
- Metropolitan Tunnel Redundancy Program Update. Meeting materials and presentation, 10/16/2019
- Metropolitan Tunnel Redundancy Program Update on Tunnel Hydraulics and Program Support Services Consultant Key Personnel. Meeting materials and presentation, 04/17/2019
- Program Support Services for the Metropolitan Tunnel Redundancy Program JCK Underground, Inc. Contract 7655. Meeting materials and presentation, 03/20/2019
- Update on the Consultant Support Structure for the Metropolitan Tunnel Redundancy Program. Meeting materials, 10/17/18
- Approval: Two-Tunnel Alternative for Redundancy of the Metropolitan Tunnel System. Meeting materials and presentation, 02/15/2017
- Special Meeting of the Board of Directors on Metropolitan Tunnel Redundancy. Meeting materials, 10/06/2016
- Program update for Waltham City Council, 06/16/2025
- Public Information Session at Needham Town Hall, 02/05/2025
- Program update for the MWRA Water Supply Citizens Advisory Committee (WSCAC), 01/14/2025
- Program update for the MWRA Advisory Board, 07/18/2024
- Program update for the MWRA Advisory Board, 04/18/2024
- Program update for MWRA Water Supply Citizens Advisory Committee (WSCAC), 01/09/2024
- Program overview for the Weston Select Board, 01/10/2023
- Program update for MWRA Water Supply Citizens Advisory Committee (WSCAC),
01/10/2023 - Program overview for the Needham Select Board, 11/22/2022
- Program update for the MWRA Advisory Board, 11/17/2022
- Program update for Town of Wellesley Board of Public Works, 11/15/2022
- Program update for MWRA Water Supply Citizens Advisory Committee (WSCAC), 02/08/2022
- Program overview for Waltham City Council, 06/21/2021
- Metropolitan Tunnel Redundancy Program update for the MWRA Advisory Board, 01/21/2021
- Metropolitan Tunnel Redundancy Program update for the MWRA Advisory Board, 09/20/2018
- MWRA Advisory Board Special Meeting on Water Redundancy, (via MWRA Advisory Board website), 12/08/2016
- Meeting No. 7, November 7, 2024
agenda | presentations | summary - Meeting No. 6, September 22, 2022
agenda | presentations | summary - Meeting No. 5, June 15, 2022
agenda | presentations | summary - Meeting No. 4, December 1, 2021
agenda | presentations | summary - Meeting No. 3, August 4, 2021
agenda | presentations | handouts | summary - Meeting No. 2, June 2, 2021
agenda | presentations | handouts | summary - Meeting No. 1, April 7, 2021
agenda | presentations | handouts | summary
Contact Us
Please contact Carmine DeMaria, MWRA Community Relations Coordinator, or Tunnels.Info@mwra.com if you have any questions or concerns about the Metropolitan Water Tunnel Program.