They are part of New York’s skyline: hundreds of spindly construction cranes like the one that toppled over the weekend, pulverizing parts of a city block below and killing seven people. As the machines work furiously amid a supercharged building boom, experts say it’s always a risk.
Operating cranes in a city of 8.2 million people where apartments and offices are stacked so closely and on top of one another is especially tricky.
“Because of the tightness of a construction site in New York City, there’s always the problem of having less space, and also there’s the problem that if anything does go wrong, there are a lot of people at risk,” said Gene Corley, a structural engineer.
Six construction workers and a woman in town for St. Patrick’s Day were killed Saturday when the crane broke away from an apartment tower under construction and toppled like a tree onto buildings as far as a block away. The last three bodies were found Monday.
The crane was being lengthened with a new section — a process known as “jumping” — when it tumbled to the street. A 6-ton steel collar used to secure he crane to the building came loose, the buildings department said.
When the collar fell, it clanged into another collar on the ninth floor that acted as a major anchor, and without that support the counterweights at the top of the crane’s tower pitched it over, the buildings department said.
Pieces of the crane hurled themselves forward as they crashed to the ground, coming to a rest a full block away. By the time it was over, a brownstone was pulverized, at least seven other buildings were damaged, and 24 people were injured.
The scale of the damage gives some sense of a construction crane’s heft and span.
This particular model, known as a tower crane, had a 200-foot mast, comprising 13 sections that each weighed 11,000 pounds. The cab and deck at the top of the mast weighed about 50,000 pounds, the boom weighed about 20,000 pounds, and the counterweights added up to about 80,000 pounds, city officials said.
That amounts to about 150 tons of steel — the weight of two Boeing 737 jetliners — much of which came cascading down on a heavily populated block of Manhattan.
On a typical day at a construction site, a crane might be manned by two or three people; for special operations like extending its height, a larger crew would be on hand.
Some residents in the neighborhood where the crane collapsed, including one community leader, had raised concerns about the crane in recent weeks, including whether it was properly attached to the building.
The city had answered 38 complaints and issued slightly more than a dozen violations in the past 27 months to the construction site — not unusual for a major New York City construction project like the 43-story condominium tower.
None of the violations was related to the crane, Mayor Michael Bloomberg said. The city said the crane had passed inspection Friday, the day before it plunged to the ground.
Nationally, the number of crane-related deaths has fluctuated over the past decade, with 72 in 2006 and 85 in 2005, according to preliminary figures.
The city had eight crane-related accidents in 2007, compared with five in 2006, according to the buildings department. There were no crane-related fatalities in 2007 and two the previous year. About 250 cranes operate on any given day in the city.
Last year one crane dropped 7 tons of steel onto a trailer where Goldman Sachs Group Inc. is building a tower across the street from the site of the Sept. 11 terrorist attacks, injuring an architect inside. In 2006, a 13-foot piece of a crane mast that was being dismantled fell and crushed a taxi cab near Union Square.
Ed Wiener, who lives in West Orange, N.J., and works near the accident scene, said Monday that he is leery of cranes.
“I always walk on the other side of the street when I see them,” he said. “I don’t want to be under one of them. They pick up a ton of cement and the thing is swinging and people walk under them like it’s an everyday occurrence.”
Associated Press writer Karen Matthews contributed to this report.
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