Under the Hudson

Devising a means to carry water beneath the Hudson River was the most challenging aspect of the Catskill aqueduct construction. Engineers identified the area around Storm King mountain, and began an arduous process (with many failed attempts) of boring into the earth below the riverbed to locate bedrock. The tunnel was eventually built 1,100 ft below ground, which included 950 ft below the Hudson River bedrock. This bedrock buffer between the tunnel and the river bottom allowed the aqueduct to withstand the colossal pressure exerted by the river.

A black and white photo of an underground tunnel under construction. It looks to be about two stories tall and wide. there are a group of men, dirty from working underground, gathered looking at the camera. There are rail tracks inside the tunnel and various equipment erected inside the tunnel. — Eight men in tunnel. Aqueducts – Hudson River Crossing – Catskill Aqueduct construction. Source: Library of Congress. Link.

“Glaciers, earthquakes and floods had, over eons, created a patchwork of geological conditions that would ultimately take the aqueduct through what geologists know as the Catskill Plateau, the Great Appalachian Valley, and the mountainous Hudson Highlands, the Piedmont Region of Westchester County and the Coastal Plain represented by Long Island. Plotting an aqueduct through such varying terrain would be no mean feat.”

— From Liquid Assets by Diane Galusha.

A black and white photo taken from high on a mountain overlooking the Hudson River below. There is a rounded mountain on the other side of the river, right on the edge of the shore. There are plumes of smoke rising from the shore. Four structures forming a row across the river rise from the water. — Catskill Aqueduct construction: Hudson River Crossing, looking west from Breakneck Mountain toward Storm King, showing borings being driven from scows, 1907. Source: Library of Congress. Link.

A black and white photo looking at a landscape from a high perspective. Below is a river surrounded on both sides by cliffed mountains. The sky and surface of the water looks misty and moody. — Hudson pressure tunnel. General view looking north at site of tunnel crossing. Breakneck mountain on right, Storm King on the left. August 29, 1916. Source: NYPL. Link.

A blue/purple tinted line drawing of a cross section of the Hudson River where the Catskill Aqueduct goes underneath. — Cross section of Hudson River crossing looking south towards West Point. From *New York City’s Catskill Mountain Water Supply*, by Alrfed D. Flinn, 1918. Source: Jstor. Link.

“Starting with a series of buried masonry conduits seventeen feet high and seventeen and a half feet wide running more than thirty miles along the mountain slopes, the aqueduct plunged through thirteen and a half miles of tunnels that had been blasted through solid rock, before dropping deep under the Hudson River and rising up again before finally reaching New York City. Not a single pump was required; the water traveled the entire one hundred miles by gravity.”

— From The Catskills: Its History and How It Changed America by Stephen M. Silverman and Raphael D. Silver

A blue/purple tinted line drawing that traces the elevations from the Gilboa Dam in the Catskills to NYC. — Profile of Catskill Mountain Water supply system from Gilboa Dam to Silver Lake terminal reservoir, showing the elevations of the reservoirs and the different parts of the aqueduct. The Hudson River Crossing can be seen in the middle row where there is a deep depression in the line. From *New York City’s Catskill Mountain Water Supply*, by Alrfed D. Flinn, 1918. Source: Jstor. Link.

A blue tinted line drawing map featuring the Catskill watershed and reservoirs at the top (North), the Hudson River in the middle, and NYC at the bottom. The Catskill Aqueduct is shown as a dark line connecting the Watershed with the City, crossing over halfway through. — Map of the Catskill Mountain Water System, showing the Catskill Aqueduct Hudson River Crossing, and the system’s relation to the Croton and Ridgewood Systems. Source: Jstor. Link.

“Field studies and test borings were conducted along the route to determine such things as drainage, location of fold and fault zones, contours of underground bedrock, probable depth of buried gorges and the nature of underground water circulation. These investigations led to two major changes in the aqueduct route as initially proposed: The out-take of the Ashokan Reservoir was shifted from West Hurley to a point nearer the dam site at Olive Bridge to take advantage of more favorable topographical conditions; and the Hudson River crossing, first proposed for New Hamburg, was changed to Storm King further south to avoid several faults, penetration of problematic limestone, and the necessity of building a nine-mile-long pressure tunnel from Marlboro to Fishkill.”

— From Liquid Assets by Diane Galusha.

A black and white photo of an underground chamber where men, both Black and white, are handling equipment surrounding a large steel dome structure that looks to be about 10ft tall. A ring of massive bolts, about the size of a man's head are dotted around the base of the dome. — Hudson pressure tunnel. Fourteen-foot cast-steel dome for Drainage shaft showing method of stressing anchor-bolts. February 19, 1914. Source: New York Public Library Digital Collections. Link.

A black and white photo of five men standing around a wooden box with a hand-pulled lever in it. The men are wearing hard hats and some are uniform hats. A man has his hand on the lever about to pull it. — Hudson pressure tunnel. Mayor William J. Gaynor firing blast to connect East and West headings. In the group, left to right, are Consulting Engineer John R. Freeman, Commissioner Charles Strauss, Chief Engineer J. Waldo Smith, Mayor Willian J. Gaynor and Commissioner John F. Galvin. January 30, 1912. Source: New York Public Library Digital Collections. Link.

A birds eye view looking down at a construction zone of excavated earth. There is a large steel dome and another one beside it under construction, revealing the shaft going underground, surrounded by steel beams protruding up into the air. Three men are standing on the rim of this shaft looking up at the camera. — Hudson pressure tunnel. General view at top of Drainage shaft. October 27, 1913. Source: New York Public Library Digital Collections. Link.