City Water Tunnel No. 3

Concreted section of City Water Tunnel No. 3. May 10, 1978. Carl Ambrose, New York City Department of Environmental Protection.It is the largest and longest running capital project in New York City’s history and among the largest engineering projects in the world. When it is finished and all the construction shafts have been closed up, it will have completely disappeared from view, up to 800 feet below ground. The only evidence of its existence will be the assurance that when you and many subsequent generations need to bathe, cook, or fight a fire there will be plenty of water to do so. Its name may be prosaic—City Water Tunnel No. 3—but its function is essential to the life of New York.

Construction of City Water Tunnel No. 3 began in 1970. The 13-mile Stage 1 section went into service in 1998. Stage 2, consisting of a 5.5-mile section in Brooklyn that connects to a 5-mile section in Queens, was completed in 2001. By the mid 2010s, a Brooklyn/Queens section will deliver water to Staten Island, Brooklyn and Queens. Tunneling on the Manhattan section of Stage 2 began in 2003, was completed in 2006 and is expected to begin water delivery by 2013. When finished, City Water Tunnel No. 3, ranging in diameter from 10 feet to 24 feet, will span 60 miles.

To ensure the long-term viability and sustainability of the New York City water supply system, the completion of City Water Tunnel No. 3 will allow for the shut-down, inspection and repairs to City Water Tunnels No. 1 and 2, which were put in service in 1917 and 1936 respectively and have been in continuous service ever since.

View down shaft for City Tunnel No. 2. Brooklyn, 1931. New York City Department of Environmental Protection.

Completed in 1936, City Water Tunnel No. 2 distributes Catskill and Delaware water from Hillview through the Bronx and Queens to Brooklyn where it meets City Water Tunnel No. 1 and sends water through a newer tunnel to Staten Island.

Framework of Concrete Form for City Tunnel No. 1. 1914. New York City Department of Environmental Protection.

Completed in 1917 as part of the new Catskill water supply, City Water Tunne lNo. 1 now distributes Catskill and Delaware water from the Hillview Reservoir, in Yonkers just north of the city line, through the Bronx and Manhattan to Brooklyn. The form shown here transitioned a 14-foot diameter shaft to a 12-foot diameter section of tunnel.

Williamsburg Conduit for City Tunnel No. 1. 1925. New York City Department of Environmental Protection.

A section of tunnel conduit in Brooklyn. Completion of City Water Tunnel No. 3 will allow for the first inspection and repairs of the oldest distribution tunnel since it was opened nearly a century ago.

Parts of steel interlining of City Tunne lNo. 2. 1932. New York City Department of Environmental Protection.

City Water Tunnel No. 1 is 18 miles long, with diameters from 11 to 15 feet. City Water Tunnel No. 2 is 19 miles long, with diameters from 15 to 17 feet. These two concrete-lined, deep rock pressure tunnels can deliver a combined flow of two billion gallons of water per day.

Map. New York City Department of Environmental Protection.

City Water Tunnel No. 3 is a four-stage project beneath every borough but Staten Island.

Cross sectional diagram.

City Water Tunnel No. 3 is very deep below us, 800 feet below Roosevelt Island, or nearly twice as deep as the first two water distribution tunnels.

Shaft excavation. 1970. Carl Ambrose, New York City Department of Environmental Protection.

The opening of a shaft at the beginning of work on the first phase of City Water Tunnel No. 3.  Note the similarity to City Water Tunnel No. 2 shaft image from 1931.

Concreted section of City Water Tunnel No. 3. May 10, 1978. Carl Ambrose, New York City Department of Environmental Protection.

Steel form for concreting. 1978. Carl Ambrose, New York City Department of Environmental.

Phase 1 of City Water Tunnel No. 3was dug largely in the traditional manner of earlier tunnels: blasting a large pathway and using a smaller form to fashion smooth tunnel walls. Tunnel boring machines (TBMs), introduced in the 1980s, offer a more efficient process.

TBM being assembled in City Tunnel No. 3. 1994. Carl Ambrose, New York City Department of Environmental Protection.

Prior to the use of tunnel boring machines (TBMs), all deep rock excavations were done by drilling and blasting. Like tunnels before it, stage 1 of City Water Tunnel No. 3 was dug by this traditional method. Starting with Stage 2, all excavation is by TBMs.

City Water Tunnel No. 3 (temporary rail tunnel on left). January 19, 2006. Carl Ambrose, New York City Department of Environmental Protection.

The ongoing work such as this on stage 2 is expected to be complete by 2013. Next up would be stage 3—a 16-mile section connecting the Kensico Reservoir in northern Westchester to Van Cortlandt Park in the Bronx—and stage 4—a 14-mile section to service eastern portions of the Bronx and Queens.

Welders at work on Tunnel No. 3. January, 2008. Carl Ambrose, New York City Department of Environmental Protection.

Twenty-three workers have died since the start of construction in 1970. Any death is tragic but modern construction methods and regulations make for substantially safer conditions than existed a century ago. An average of over 40 men died during each of the seven years of construction on City Water Tunnel No. 1 and the Catskill Aqueduct.

City Water Tunnel No. 3, Stage 1 excavation. February 12, 1972.

Above is Carl Ambrose’s favorite photo. “It really shows the work going on; men are in the front and machinery is in the back. It shows the rock and the entire environment you are working in. That’s the tunnel. Lighting for this photograph was from huge reflectors I couldn’t move. It is not easy working like this but you have to make the best of it. Sometimes the results really make you proud.”