HOUSE DEMOCRATS will call for expansion of the Massachusetts Water Resources Authority service area when they take up the governor’s massive housing policy and borrowing bill later this spring. House Speaker Ronald Mariano didn’t specify which areas he wants to see newly served by the MWRA, although he mentioned Weymouth and Brockton, but the authority has been busy in recent years preparing for potential expansions into dozens of new communities.

“Another critical step in the effort to increase housing production is ensuring that the Commonwealth is equipped with the infrastructure needed to support a significant increase in development. That’s why the House’s bill will unlock the full potential of the MWRA by expanding its area of service to provide clean water to future housing developments,” the speaker said Thursday morning in an address to the Greater Boston Chamber of Commerce.

The MWRA was created by the Legislature in 1984 and currently provides wholesale water and sewer services to 3.1 million people and more than 5,500 businesses in 61 communities in eastern and central Massachusetts.

Since October 2022, the MWRA has had three feasibility studies completed, looking at the potential to expand the MWRA system in the Metro West area (Acton, Ayer, Bedford, Chelmsford, Concord, Groton, Holliston, Hopkinton, Hudson, Lincoln, Littleton, Maynard, Natick, Sherborn, Stow, Sudbury, Wayland, Wellesley, Westborough, Westford and Weston), the Ipswich River Basin (Beverly, Danvers, Hamilton, Ipswich, Middleton, Lynn, the Lynnfield Center Water District, Peabody, Salem, Topsfield, Wenham and Wilmington) and to the South Shore (Abington, Avon, Brockton, Cohasset, Hanover, Hingham, Norwell, Scituate, Rockland, Weymouth and the Union Point development).

“Regarding potential water system expansion, all three studies are intended to quantify the Authority’s capacity to serve new customers, develop alternatives for new infrastructure that would expand the Authority’s ability to serve new communities, and provide planning-level cost estimates for these alternatives,” the studies each say.

Two of the reports specifically allude to the fact that water infrastructure is a crucial prerequisite for population growth and the kind of revved up housing production that most state leaders want to encourage.

The South Shore report says that many of the towns studied “continue to experience challenges in meeting the water demands and growth expectations of their communities” and the Metro West report concluded that towns in that region “may experience challenges in meeting water demands and growth expectations of their communities.”

The Metro West study calculated a maximum water demand of 57.1 million gallons per day and an average of 30.8 million gallons per day for the towns studied. It concluded that “the MWRA’s water system has sufficient capacity to supply the current maximum day demand of the MetroWest communities in the study area under normal operating conditions.”

The report gave an “opinion of probable project cost,” estimating that the five independent projects needed to service all communities studied could cost as much as $1.3 billion in 2028 dollars and take as long as 30 years.

For the South Shore and Ipswich River Basin, the MWRA’s studies concluded that capacity either is or could be available to meet the projected demand (48.9 million gallons per day for the Ipswich River Basin and 40.5 million gallons per day for the South Shore towns).

An expansion into the Ipswich River Basin “could range from $130 million to well over $1 billion” while the South Shore expansion “could range from $540 million to well over $1 billion,” the studies said. In both cases, the timeline for the final design, construction and startup of the new infrastructure “could range from 7 to 10 years for more limited expansions, to more than 20 years for larger system expansions.”

Expansion of the MWRA system is not only relevant to the communities that might be part of those expansions, but also to the Western Mass. towns that surround the system’s primary source, the Quabbin Reservoir.

Sen. Jo Comerford of Northampton and Rep. Aaron Saunders of Belchertown filed a bill that would impose a 5-cent-per-1,000 gallon excise on Quabbin water. The lawmakers estimate the tax would produce $3.5 million, which would be directed to Quabbin watershed communities and local nonprofits with a focus on these towns’ health, welfare, safety and transit.

“The Quabbin Reservoir provides life for eastern Massachusetts and allows the eastern part of the state to grow and expand — and yet for far too long, far too long, the recompense for towns that steward this water has been a pittance relative to the value,” Comerford said last year.

One provision of the bill, which is before the Joint Committee on Environment and Natural Resources under an extension order until April 12, would mandate that, as the MWRA explores opportunities to expand into new communities, that it look into supplying water for the communities directly in the Quabbin region, as well as towns in the Westfield River, Chicopee River, Connecticut River and Millers River Valley basins.

As it has studied the potential for expansion, the MWRA is also deeply enmeshed in a project to create redundant water flow systems that would enable them to address the infrastructure vulnerabilities associated with the tunnel system that provides 60 percent of the water to eastern Massachusetts communities. Authority officials have been aware of the system’s problems for years and in 2016 began publicly laying out a plan to address them.

The Metropolitan Tunnel System includes the 5.4-mile City Tunnel, built in 1950 and running from Weston under Newton to Chestnut Hill; the 7-mile City Tunnel Extension, built in 1963 and running under Brighton, Cambridge, Somerville, and Medford to the Malden line; and the 6.4-mile Dorchester Tunnel, which was built in 1976 and stretches from Chestnut Hill under Brookline to Morton Avenue in Dorchester.

The MWRA said in 2016 that many of the cast iron and steel pipes and valves integral to the tunnel system have long since passed their life expectancy estimates and were in “poor condition.” The authority said it was unable to even inspect the aging equipment without shutting the system down, which is not an option due to the lack of a redundant system to keep water flowing to residents and businesses in eastern Massachusetts.

“They need to be maintained and right now we have no ability to bring the tunnels down to maintain them,” MWRA Executive Director Fred Laskey said in a 2016 interview. “If something went wrong and there was a leak that developed, it would be catastrophic.”

The MWRA submitted a final environmental impact statement for the project in February and comments on it are due next week. The authority said the Executive Office of Energy and Environmental Affairs is due to issue a certificate for the project by April 1.

The project proposes the construction of two new deep rock water supply tunnels, about 15 miles long in total and running 200 to 400 feet below the ground surface of several communities. The redundant tunnels would originate at the westernmost point of the Metropolitan Tunnel System near the interchange of Interstates 90 and 95, and one would run north towards Waltham and the other would head towards Boston.

“The Program was conceived to address outstanding challenges, primarily the inability to maintain or repair the existing Metropolitan Tunnel System or readily respond to emergencies as boil water orders are needed when implementing back-up water supply measures,” the authority wrote in the environmental impact statement. “As a result of the construction of the two new deep-rock tunnels, the Program would allow the MWRA to take its aging existing water tunnel system offline to be rehabilitated without interrupting water service to over 2.5 million water customers.”

Construction for that project is estimated to take 8 to 12 years and is planned to occur between 2027 and 2040. The impact statement did not include a specific cost estimate, but in 2016 the authority said the estimated midpoint cost of the two projects was a combined $1.475 billion.