Hell Gate Explosion

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On October 10, 1885, a major impediment to navigation on the East River, a huge rock island called Flood Rock, was blown up.  This rock island was located between Astoria (Queens) and Wards Island (Manhattan) in a dangerous narrow section of the East River called Hell Gate.  The explosion was watched by thousands of spectators and felt theoughout the city.  

Hell Gate is a narrow tidal strait in the East River which connects the Upper Bay of New York Harbor and Long Island Sound, a place of rocks and dangerously converging tide-driven currents. It is located between Wards Island (part of Manhattan) and Astoria (Queens).(6) This choke point on the East River was, and still is, a challenge to navigation.(8)

During the 19th century, the U.S. Army Corps of Engineers undertook a decades-long project to clear major obstacles from Hell Gate.(9)(1) In the 1880s the massive (9 acre) stone island called Flood Rock was its target. Tides hitting the rock created turbulent currents and whirlpools in the busy narrow channel, impeding navigation. The Corp’s plan was to employ explosives, a huge amount of explosives, to widen and deepen the Hell Gate channel and to lessen the swirls and eddies. During the nine years leading up to 1885, a mine shaft was dug deep into Flood Rock with tunnels branched out at various levels. Holes drilled into the ceilings were filled with 283,000 pounds of explosives. When the day came to set off the explosion, the mine shaft was flooded with water to help deaden the sound and mitigate the shock in surrounding areas, and on October 10, 1885 the largest single explosion recorded to date broke up the base of the rock. (1)(5)(3) Flood Rock, now full of cracks, settled lower in the water.(7) Surface blasting addressed some remaining above-surface areas. General Newton, in charge of the project, declared the result a complete success.(4) Removal of the broken rock would take place over time and be done by dredges.(4) The shock of the deep explosion was felt all over the city.(2)

An estimated 200,000 spectators lined the Astoria Long Island shore, the river front of Manhattan, Wards and other islands in the East River, and crowded on many commercial and private vessels.(10)

Note: Wards Island (south) is now conjoined with Randalls Island (north). Before being filled in, the passage between them was called “Little Hell Gate”. They are part of the borough of Manhattan.
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For a map of Hell Gate click on http://www.nan.usace.army.mil/portals/37/docs/history/hellgate.pdf

Sources:  

1. “The Conquest of Hell Gate.” U.S. Army Corps of Engineers.
www.nan.usace.army.mil/portals/37/docs/history/hellgate.pdf
accessed February 6, 2020
2. "Feeling the Shock: An Artificial Earthquake Created by the Explosion,” The New York Times, October 11, 1885, p.2.
3. “Flooding the Great Mine: All Ready for the Hell Gate Explosion. Flood Rock Cleared of Buildings and Water Let Into the Excavation – What the Spectators will See.” The New York Times, October 10, 1885, p.5.
4. “Fragments of Flood Rock: Gen. Newton Pronounces the Result a Complete Success.” The New York Times, October 11, 1885, p.1.
5. “The Great Explosion,” The New York Times, October 11, 1885, p.8.
6. “Hell Gate.” The Encyclopedia of New York City, Kenneth T. Jackson, ed., New Haven: Yale University Press, 1995, p. 538.
7. “The Ruins at Flood Rock: Belief that the Explosion did its Work Well. The Shell of the Rock Gives Evidence of Having Settled – Hundreds of Relic Hunters Visit the Scene.” The New York Times, October 12, 1885, p.1.
8. “Transiting Hell Gate,” Liberty Yacht Club, July 25, 2016.
www.libertyyachtclub.org/2016/07/25/transiting-hell-gate/
accessed February 6, 2020
9. The U.S. Army Corps of Engineers, established in 1775, became a separate and permanent branch of the Army March 16, 1802. Among its many responsibilities was the elimination of navigational hazards.  available at the Army Corps of Engineers website:
www.usace.army.mil/missions. 
accessed February 6, 2020
10. “Viewing the Explosion: The Great Crowds Which Thronged the East River Front,” The New York Times, October 11, 1885, p.2.