Hultman Aqueduct, Massachusetts

The John J. Carroll Water Treatment Plant (CWTP), has been in operation since 2005, and is one link among many in the chain of facilities comprising Boston’s water supply. It is connected to the newer MetroWest Water Supply Tunnel, and the older Hultman Aqueduct. For more than 17 miles, and for over 60 years, the Hultman Aqueduct carried nearly all of metropolitan Boston's water, a crucial link in the only water system of any major city in the country that didn't have a backup. By the late 1990s, the surface level pipeline built in 1939 (which snaked through suburban Boston as an earth-covered mound), was crumbling - losing around 400,000 gallons of water per day.  A second tunnel, the MetroWest Water Supply Tunnel - buried deep underground - went online in 2003, after seven years of construction, making it possible to take the Hultman Aqueduct off-line, while it was being refurbished. In 2013, rehabilitation of the Hultman Aqueduct was completed, providing the desired full redundancy from Marlborough to Weston.