Pressure Aqueducts

After WWII, the remaining portions of the Pressure Aqueduct system came online as follows:

Portion of the
Pressure Aqueduct
Chicopee Valley
Quabbin Reservoir to Chicopee1950CVA Aqueduct redundancy project in design (2000-2001)
City TunnelHultman Aqueduct
Terminus to Chestnut Hill Reservoir
1951Cochituate Aqueduct
City Tunnel ExtensionChestnut Hill Reservoir part way to Fells Reservoir1961 
Cosgrove TunnelWachusett Reservoir to start of Hultman Aqueduct1965 
Dorchester TunnelCity Tunnel at Chestnut Hill Reservoir part way to Blue Hills Reservoir1978Sudbury Aqueduct and Chestnut Hill
Reservoir taken offline

As these sections of the Pressure Aqueduct have come online, the need for pumping has been reduced since more of the service area can be supplied by gravity. Older facilities which originally provided a level of redundancy to the new tunnels were eventually retired from use. More reliance was placed on the newer, partially completed system to the point where it is now relied upon to deliver 85 percent of metropolitan demand. Many of these expansions looked to use gravity for supplying water instead of costly pumping.


Around 1951, several pump stations were constructed to take suction from WASM 3 and supply Extra or Intermediate High Service to the fast growing suburbs along Route 128.

By 1978, the Boston Low demand had been transferred to the Weston Aqueduct Supply Mains (Nos 1 and 2), supplemented by pressure reduction facilities from the City Tunnel. The Northern Low demand had been transferred to the Weston Aqueduct Supply Mains (Nos 3 and 4), supplemented after 1961 by pressure reduction from the City Tunnel Extension. The only demands remaining on the Sudbury Aqueduct were those of the Southern High and the Southern Extra High service areas, but these were, by this time, large enough to require its full capacity. Completion to the Dorchester Tunnel in 1978 allowed the demands of the southern systems to be removed from the Sudbury Aqueduct. However, because there is no redundancy for the Dorchester Tunnel, the facilities taken off line in 1978 must remain in stand-by status.

Although completion of the Dorchester Tunnel made it physically possible to remove the Sudbury Aqueduct/Chestnut Hill systems from active use, the primary reason for doing so was water quality. The Sudbury River did not meet quality standards without treatment and the uncovered Chestnut Hill reservoir, located in a highly urbanized area, further deteriorated in quality.

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