Deep under the New York City boroughs of Brooklyn and Queens is a water tunnel waiting for the water to be turned on. Actually, it is waiting for money to flow.

In 1954, the city decided it needed a backup for two water tunnels that carry more than a billion gallons of water a day to the city’s 8 million residents. Conceived in those planning sessions, water tunnel No. 3 will provide redundancy and enable the city to shut down water tunnels No. 1 and No. 2 for inspection and repair for the first time since they entered service in 1917 and 1936, respectively.