The Wachusett Aqueduct carries water from the Wachusett Reservoir

Wachusett Reservoir

The Wachusett Reservoir is the second largest body of water in the state of Massachusetts. It is located in central Massachusetts, northeast of Worcester. It is part of the water supply system for metropolitan Boston maintained by the Massachusetts Water Resources Authority . It has an aggregate...

 to the John J. Carroll Water Treatment Plant at Walnut Hill in Marlborough, Massachusetts

Marlborough, Massachusetts

Marlborough is a city in Middlesex County, Massachusetts, United States. The population was 38,499 at the 2010 census. Marlborough became a prosperous industrial town in the 19th century and made the transition to high technology industry in the late 20th century after the construction of the...

. It is part of the Boston, Massachusetts public water supply system, maintained by the Massachusetts Water Resources Authority

Massachusetts Water Resources Authority

The Massachusetts Water Resources Authority is a public authority in the Commonwealth of Massachusetts that provides wholesale drinking water and sewage services to certain municipalities and industrial users in the state, primarily in the Boston area.The authority receives water from the Quabbin...

 (MWRA) in the United States.

Physical characteristics

The Wachusett Aqueduct extends from the Wachusett Reservoir

Wachusett Reservoir

The Wachusett Reservoir is the second largest body of water in the state of Massachusetts. It is located in central Massachusetts, northeast of Worcester. It is part of the water supply system for metropolitan Boston maintained by the Massachusetts Water Resources Authority . It has an aggregate...

 in Clinton

Clinton, Massachusetts

Clinton is a town in Worcester County, Massachusetts, United States. The population was 13,606 at the 2010 census.For geographic and demographic information on the census-designated place Clinton, please see the article Clinton , Massachusetts....

, through Berlin

Berlin, Massachusetts

Berlin is a town in Worcester County, Massachusetts, United States. The population was 2,866 at the 2010 census.- History :Berlin was first settled in 1665 and was officially incorporated in 1812....

 and Northborough

Northborough, Massachusetts

Northborough is a town in Worcester County, Massachusetts, United States. The official spelling of the town's name is "Northborough", but the shorter spelling "Northboro" is also used...

, to the John J. Carroll Water Treatment Plant at Walnut Hill in Marlborough, Massachusetts

Marlborough, Massachusetts

Marlborough is a city in Middlesex County, Massachusetts, United States. The population was 38,499 at the 2010 census. Marlborough became a prosperous industrial town in the 19th century and made the transition to high technology industry in the late 20th century after the construction of the...

. (Before the treatment plant was activated in 2005, the aqueduct

Aqueduct

An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....

 carried water to the nearby Sudbury Reservoir.) This 9 miles (14.5 km) long water system consists of 2 miles (3 km) of hard rock tunnel and 7 miles (11 km) of 11 feet (3.4 m) high horseshoe-shaped underground aqueduct constructed of non-reinforced concrete with a brick-lined invert. It is not constructed entirely underground and there are several elevated over crossings.

Modern use

Until the 1960s, the Wachusett Aqueduct was the main conduit used to deliver water from the Wachusett Reservoir

Wachusett Reservoir

The Wachusett Reservoir is the second largest body of water in the state of Massachusetts. It is located in central Massachusetts, northeast of Worcester. It is part of the water supply system for metropolitan Boston maintained by the Massachusetts Water Resources Authority . It has an aggregate...

. At that time, it carried 300 million USgals (1,135,623.6 m³) of water each day (13 m³/s). The Cosgrove Tunnel replaced it in 1965 as the primary water transmission aqueduct. Because of the construction of the Walnut Hill Water Treatment Plant in Marlborough

Marlborough, Massachusetts

Marlborough is a city in Middlesex County, Massachusetts, United States. The population was 38,499 at the 2010 census. Marlborough became a prosperous industrial town in the 19th century and made the transition to high technology industry in the late 20th century after the construction of the...

, the Cosgrove Tunnel was shut down in 2003 in order to make the large piping connection between the new treatment plant and MWRA’s new MetroWest Water Supply Tunnel

MetroWest Water Supply Tunnel

The MetroWest Water Supply Tunnel is an advanced underground aqueduct that supplies potable water to residents of much of Greater Boston. It is part of the Massachusetts Water Resources Authority water supply system....

. The MetroWest

MetroWest

MetroWest is a cluster of cities and towns lying west of Boston and east of Worcester, in the US state of Massachusetts. The name was coined in the 1980s by a local newspaper....

 Tunnel extends east 18.6 miles (29.9 km) from Walnut Hill to Weston

Weston, Massachusetts

Weston is a suburb of Boston located in Middlesex County, Massachusetts, United States in the Boston metro area. The population of Weston, according to the 2010 U.S. Census, is 11,261....

. During that shutdown, the Wachusett Aqueduct was the primary method of transmission of about 240 million USgals (908,498.9 m³) of water per day.