Building New York's water supply
One of the greatest marvels of the 20th century, buried underground
Alex Q. Arbuckle
1906-1917
At the start of the 20th century, engineers for New York City determined that in order to accommodate the growing metropolis' demand for water, they would have to accomplish an engineering feat of almost unprecedented scale.To find a source of clean water that could be feasibly delivered to the city, engineers had to look far north, to the Catskill Mountains. The plan called for the damming of Esopus Creek, which would flood thousands of acres of farmland, forming a massive reservoir. Water would then travel through 163 miles of subterranean aqueducts and two smaller reservoirs on the way to the city.
Beginning in 1905, the towns, forests and farms on the site of the future Ashokan Reservoir were razed, and in the fall of 1907 construction of the main dams began. The reservoir would be impounded by a chain of masonry and earthen dams totaling five miles in length. The Olive Bridge dam, sitting athwart Esopus Creek itself, would be nearly a mile long and reach a top height of 240 feet above its foundation.Between 1907 and 1915, tens of thousands of workers formed millions of tons of earth, stone and concrete into a reservoir large enough to hold approximately 123 billion gallons — enough to drown Manhattan under 28 feet of water.
The Catskill Mountain water system being constructed for New York City is one of the most notable engineering enterprises ever undertaken... ranking with the interoceanic canals at Suez and Panama. - Century Magazine, 1909
The great pyramid of Cheops, in Egypt, was originally 756 feet square at its base and 481 feet high. Its volume... is only one eighth that of the material to be moved in building [the Ashokan Reservoir]. - Alfred Douglas Flinn, Engineer, Dept. of the Board Of Water Supply of the City of New York, 1909
Meanwhile, farther south at the village of Kensico, about 15 miles north of New York, another reservoir was built. The Kensico Dam, built over the site of a previous earth and gravel dam, was constructed from 1913 to 1917. It reaches 307 feet above its foundation and stretches over 1,800 feet long, impounding a reservoir large enough to hold 30 billion gallons.
In 97 A.D. [Rome] had no fewer than nine aqueducts, with an aggregate length of 263 miles; but if the water that all those aqueducts could carry (estimated at 84,000,000 gallons per day) were put into New York's Catskill aqueduct, it would rise only to the height of about three feet and three inches. - Alfred Douglas Flinn, Engineer, Dept. of the Board Of Water Supply of the City of New York, 1909
Farther south in Yonkers, just north of New York City, the Hillview Reservoir was built by scraping away the top of a flat hill and forming it into a concrete-lined bowl with a capacity of 900 million gallons. The Hillview Reservoir would serve as the distribution point for the Catskill water flowing into the city.
Connecting this series of reservoirs was possibly the most impressive (and invisible) portion of the project — the Catskill Aqueduct, comprised of some 163 miles of subterranean tunnels.Of the aqueduct’s considerable length, 55 miles was built in a “cut-and-cover” design, in which a shallow trench was dug and filled with egg-shaped lengths of tunnel, then heaped over with earth.
In other sections, the topography required smaller, steeper grade tunnels to be dug straight through rock in order to avoid lengthy detours.
While in the cut-and-cover and grade tunnels the water flows freely with gravity, in other sections it has to be forced with pressure. Halfway between the Ashokan Reservoir and New York City, the aqueduct turns east and dives 1100 feet beneath the bed of the Hudson River before rising again on the far side.
Though the aqueduct itself was finished in 1917 with the completion of New York City Water Tunnel No. 1, which stretches from the Hillview Reservoir down through the Lower East Side of Manhattan, it would take another eight years for the entire Catskill system to be fully operational.The Catskill system now delivers around 400 million gallons of water to New York City every day. But that accounts for only about 40% of the city’s water — just a couple decades after the completion of the Catskill system, another aqueduct system was built to bring water from the Delaware River, which now provides half of the Big Apple’s famously inimitable tap water.
Visit Premier Exhibitions at 417 5th Avenue to see the past become present again at "Retronaut's New York." This pop-up exhibition of extraordinary, digitally restored photographs captures New York City at the turn of the 20th century. It's only open until May 15, so be sure to get down there before it’s gone.