The story
Major construction
Local wells, springs (including one on Boston Common), and rain barrels were the first sources of water for Boston residents. Jamaica Pond was used as a water source for Boston starting in 1795, using wooden pipes (later with cast iron). After several epidemics and fires which exposed the inadequacy of the water supply, the Cochituate System was constructed by the Cochituate Water Board, starting in 1845 and opening in 1848. It included a dam on the Sudbury River, creating Lake Cochituate which fed the Cochituate Aqueduct leading to the Brookline Reservoir and local storage such as the Beacon Hill Reservoir. When Boston annexed Charlestown in 1873, the Mystic Lakes system was added to Boston's water supply. The Cochituate Reservoir and Aqueduct were abandoned in 1951; none of the other reservoirs or lakes are currently in use as part of the primary or backup water supply.
The Boston Water Board constructed seven reservoirs in the Sudbury River watershed from 1875 to 1898. Water impounded in these reservoirs was delivered to the Chestnut Hill Reservoir by the Sudbury Aqueduct, completed in 1878. Some distribution mains serving the Boston Low Service area date to the period when water was gravity-fed from the Brookline and Chestnut Hill Reservoirs. (These were transferred to Weston Reservoir by 1900, and covered storage in Weston by 1978, with supplemental service from the City Tunnel and City Tunnel Extension.) In the late 1800s, water was pumped from Chestnut Hill to the Waban Hill Reservoir in Newton and the Fisher Hill Reservoir in Brookline to create the Southern High Service zone. Other pumping stations were also added: one at Alewife Brook in Somerville and another at Spot Pond in Stoneham. Some of the distribution mains carrying the now-unused supply from the Mystic Lakes, and those connecting Chestnut Hill with these mains and Spot Pond, are still supplying the northern Low Service area. Spot Pond served the northern Low Service zone, and pumped water to the Fells Reservoir to create the Northern High Service zone.
Population growth and the increasing popularity of indoor plumbing continued to put pressure on the region's water supply. After considering Lake Winnipesaukee, Sebago Lake, and the Merrimack River, the Metropolitan Water Board decided to create the world record-setting Wachusett Reservoir by damming the Nashua River in Clinton, Massachusetts. It was completed in 1905 and filled in 1908, feeding the Wachusett Aqueduct. Water travelled to the Boston area via the Weston Aqueduct and the Weston Reservoir, or via the new Sudbury Reservoir and the older Sudbury Aqueduct.
Continued growth in water demand prompted the 1926 construction of the Wachusett-Coldbrook Tunnel to tap seasonal excess water in the Ware River. The tunnel was extended to the Swift River to become the Quabbin Aqueduct. The Metropolitan Water Supply Commission began construction of the massive Quabbin Reservoir in 1936, and it took from 1939 to 1946 to fill the reservoir. The creation of the new reservoir resulted in the disincorporation of four Western Massachusetts towns.
The Chicopee Valley Aqueduct was completed in 1950. Other pressure zones were created around Route 128 suburbs in 1951 by adding several pumping stations.
Capacity was expanded in 1941 with the completion of the Hultman Aqueduct (which connected the Wachusett Aqueduct to the end of the Weston Aqueduct at Norumbega). The City Tunnel was added in 1951, connecting to the Chestnut Hill nexus. The City Tunnel Extension (1961) and Dorchester Tunnel (1978) carried high-pressure water part of the way to Fells and Blue Hills reservoirs, respectively. The Dorchester Tunnel allowed the relegation of the Sudbury Aqueduct and Chestnut Hill Reservoir to backup status, which also improved water quality. The redundant Cosgrove Tunnel was finished in 1965, allowing maintenance of the Wachusett Aqueduct.
Conservation era
Demand for water exceeded the "safe supply" of 300 million US gallons (1,100,000 m3) per day (for which precipitation is reliably available) starting in 1969. Though diverting water from the yet further westward Connecticut River was considered several times, in 1986, the MWRA instead undertook a campaign of water conservation. Demand was reduced to sustainable levels by 1989, and continued to drop to around 220 million US gallons (830,000 m3) per day by 2009.
From 1996 to 2009, the MWRA constructed sanitary covered storage tanks. These are now the primary local storage; the remaining small uncovered reservoirs are only used for backup because the water from these basins would require further treatment. The MetroWest Water Supply Tunnel was finished in 2003, allowing rehabilitation of the increasingly leaky Hultman Aqueduct.
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2010 supply failure
The 2010 Boston Water Emergency was caused by a catastrophic failure of a collar connecting two sections of 10-foot-wide (3.0 m) pipe that ruptured in Weston, Massachusetts, on May 1, disrupting the connection between the MetroWest Water Supply Tunnel and the City Tunnel. This resulted in activation of the backup reservoir system for the first time, and a boil-water order for the entire MWRA system affecting approximately two million residents of 31 cities and towns. On May 4, test results indicating the backup water supply was clean enabled lifting of the boil water order.
System expansion
Given that conservation efforts brought demand well below the MWRA-defined "safe yield", and desiring to amortize over more ratepayers the fixed costs of large projects like the MetroWest Tunnel and Deer Island sewage treatment plant, the MWRA is seeking to add more wholesale water customers, including municipalities and properties straddling the border of its service area. At the same time, certain communities in Massachusetts are facing a shortage of available water due to population growth or other factors.
From 2002 to 2009, the following municipalities and other customers have been added to the system:
Stoughton, Massachusetts
Avalon (private development on Danvers-Peabody border)
Dedham/Westwood Water District
YMCA (private customer on Salem-Marblehead border)
Reading, Massachusetts
Wilmington, Massachusetts
Lead pipe removal
MWRA and municipal water mains are made of concrete, steel, and iron, but as of 2016, about 5% of service lines (between the street and buildings, running from public to private property) in various municipalities were still made of lead. In 2016, during the Flint water crisis, the MWRA board approved $100 million in zero-interest loans for lead pipe removal. Each affected municipality is responsible for designing and operating its own program; MWRA estimates this funding will be enough to removal all lead service pipes from the entire system. MWRA has adjusted water pH since 1996 to avoid corrosion and leaching of lead from remaining pipes into drinking water.
Planned expansions and upgrades
Burlington, Massachusetts town meeting voted in 2018 to connect to the MWRA via Arlington, to make up for a partial shutdown of its Vine Brook Treatment Plant due to wells contaminated with 1,4 dioxane. Another vote to fund the second phase of construction is expected in 2021. In the meantime, Burlington gets MWRA water via Lexington if supplies drop to the point that a full outdoor watering ban is necessary (which happened during the drought of summer 2020).
In June 2020, the Lynnfield Center Water District (one of two districts in Lynnfield, Massachusetts) reached its pumping capacity, due to a combination of drought and high residential water usage during the COVID-19 pandemic in Massachusetts. It started the process of making an emergency interconnection to the Lynnfield Water District, which is supplied by the MWRA.
Because they have no alternative routes, City Tunnel, City Tunnel Extension, and Dorchester Tunnel cannot be taken out of service for more than a day for maintenance. Some of the valves that would allow that to happen are corroded or underwater. The MWRA is planning to use a tunnel boring machine to dig two new 10-foot-diameter tunnels from Shaft 55A in Weston. The new Northern Tunnel would go to the Waltham-Belmont border, and together with smaller service mains in Belmont, Arlington, and Medford, would form a loop with the City Extension Tunnel and City Tunnel. The new Southern Tunnel would go to Shaft 7C on the Dorchester Tunnel in Boston, forming a southern loop. A smaller service main in Boston would provide redundancy for the remainder of the Dorchester Tunnel. As of 2018, the project is expected to take 17 to 23 years to design and construct.
Various other "Metropolitan Redundancy Interim Improvements" would increase reliability in the short term and in the long term help eliminate any single point of failure that would necessitate a boil-water order or cause a complete water outage in any given area. This includes making a new connection for the Commonwealth Avenue Pumping Station in Newtown to low service lines, to allow the city to continue to receive water in case the City Tunnel goes out of service. MWRA also has a program to finance replacement or lining of local water mains, to maintain quality for consumers.
From Wikipedia’s article on Massachusetts Water Resources Authority, shared under CC BY-SA 4.0.5