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If you missed CUNY York College’s inaugural lecture by Department of Earth and Environmental Sciences Professor Nazrul Khandaker’s regarding the Department of Environmental Protection’s newest water tunnel – dubbed Tunnel No. 3 – have no fear. More than a decade will pass before the tunnel is actually finished.
The City’s first two water tunnels were in completed in 1917 and 1936. According to Khandaker, the need for a third tunnel was recognized in 1954. Construction began in 1970 and is expected to culminate by 2020.
“You have to admire that they thought of it well ahead,” Khandaker said adding that “Tunnel No. 3 will allow the other two tunnels to be inspected and repaired for the first time.”
Rebuilding this portion of the City’s infrastructure will cost approximately $5.8 to $6 billion in total. The tunnel is 10 feet in diameter at its narrowest, 24 feet at its widest and exists anywhere from 400 to 800 feet below ground.
Khandaker explained that 95 percent of New York City’s water supply is fed by gravity. New water valve chambers, which will be built underground in the Bronx, Central Park and Roosevelt Island, will manage the flow of water. The largest of the valve chambers is the Van Cortlandt system, located in the Bronx. Its purpose is to control the water coming from the Catskill and Delaware watershed, which provides 90 percent of the City’s water.
Construction is divided into four stages. Stages one and two address distribution capability, but do not provide any additional water supply.
The portion of the tunnel activated under Stage 1 runs from Yonkers, through Central Park and then under the East River and Roosevelt Island into Astoria. The concrete-lined tunnel is 24-feet in diameter.
The portion of the tunnel under Stage 2 has not yet been activated, but will provide water to the lower west side of Manhattan and sections of Queens, Brooklyn and Staten Island.
Stage 3 will extend a 16-mile tunnel from Van Cortlandt Park Valve Chamber in the Bronx to the Kensico Reservoir in Westchester County, thereby increasing the water supply available to the City.
Stage 4 will also start at Van Cortlandt Park and travel 14 miles under the East River into Queens.
Technology has improved in the 30-plus years since the project started. The introduction of a mechanical rock excavator called a tunnel-boring machine has increased productivity. The drilling and blasting methods used in Stage 1 were replaced by TBMs for Stage 2 and will be used again in Stages 3 and 4.