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 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 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. 2010 supply failure The 2010 Boston Water Emergency was caused by a catastrophic failure of a collar connecting two sections of 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