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04.02.2008
Tower Crane Topples
Falling machine crushes town house, kills seven
A building on 50th Street damaged by the falling crane
Aaron Seward

On the afternoon of Saturday, March 15, at a construction site at 305 East 51st Street, a 22-story-high tower crane came loose from its moorings and fell to the south. The crane’s latticed steel mast collided with the building across the street and sheared in half. The cab, jib, and rest of the mast continued to fall, damaging two other buildings on the way down and completely demolishing a townhouse on 50th Street. As of press time, rescue workers had recovered the bodies of seven people killed in the collapse, including six construction workers, and a tourist from Florida. The collapse is the latest and most serious in a recent string of accidents on high-rise building sites around the city, and has led many to question the enforcement of safety and inspection standards.

According to reports, the crane toppled after workers jumped, or raised the crane and were installing a structural steel collar to attach the mast to the concrete structure. During the installation procedure, the collar fell, smashing into another collar that attached the mast to the 9th floor and disconnecting it. Both collars then fell to the base of the tower and the destabilized crane tipped over. 

crane falls
The crane fell from this development at 305 East 51st Street. AARON SEWARD
 

While the findings of the official investigation into the disaster had yet to be released as of press time, attention seemed to be focused on a frayed nylon sling that was still attached to the fallen collar. An industry insider who requested anonymity told AN that the use of nylon slings for this kind of work is poor rigging practice because steel has sharp edges and can easily cut nylon. In fact, Section 31 of the Ironworkers’ Collective Bargaining Agreement, entitled “Safety Provisions,” contains a clause that clearly states that wire rope slings will be used instead of nylon straps. But these workers were not ironworkers, nor was there a master rigger on site supervising the jump, said the source; they were crane operators from Operating Engineers Local 14. The Department of Buildings (DOB) allows anyone who obtains a tower crane rigger’s license to supervise and execute a crane jump and does not require the presence of a professional engineer or a master rigger (a master rigger must be the officer of a company and be able to acquire $10 million in insurance). As a result, said the source, “You get these roving bands of operating engineers getting their buddies together during the weekend and jumping cranes. They don’t have anywhere near the expertise at rigging that ironworkers do. You have to ask yourself, why are they using nylon slings? It’s the first no-no. They shouldn’t even be in the toolbox.” Ironworkers execute all crane jumps on structural steel building projects, but they are rarely used for concrete projects because they are one of the most expensive trades to hire. 

According to the source, another factor that may have attributed to the fall was the crane’s floating foundation. Tower cranes are designed to be freestanding up to, and sometimes above, 200 feet; but they have to have solid concrete foundations in order to absorb lateral loads, which this crane did not have. Most developers are loath to spend a quarter of a million dollars on a temporary foundation for a crane, and so engineers have to rely on tiebacks to the building, which leaves no redundancy if the tiebacks fail. 

The real trouble with the situation is that while the workers involved in the accident were doing things by the book, the book itself has two loopholes that may have led to the catastrophe: The city allows people who are not professional riggers to execute crane jumps, and does not require stand-alone foundations for tower cranes. 

The city will most likely tighten regulations on crane jumps as a result of this accident by requiring that a master rigger and professional engineer be on site during jumps, and perhaps requiring more robust foundations. The regulations were tightened last year after sections of a tower crane fell on a taxi on 3rd Avenue during a jump, that time by requiring that a licensed tower crane rigger be on site during the process. Previously, tower crane riggers only had to be onsite when a crane was put up or taken down. 

In spite of these regulatory shortcomings, New York City’s crane laws are the most stringent in the nation, even more restrictive than those required by federal Occupational Safety and Health Administration regulations. “If you compare the number of cranes in the city with the number of injuries it’s a pretty low percentage,” said the source. “You look in the newspaper in Florida and every day you see cranes tipping over. We don’t have that. But because of our environment, when something goes wrong it goes catastrophically wrong and takes out a building.” 

The DOB’s investigation is looking into the companies involved with the construction site, including Joy Contracting, a New Jersey-based concrete company that held the crane contract and employed the operating engineers involved. The DOB is also investigating Kennelly Development Company of Manhattan, the developer of the property, a residential condominium, and the general contractor, Reliance Construction Group (RCG). Both Kennelly and RCG expressed their sympathy to the victims and said that they are cooperating with government agencies in the investigation. 

AARON SEWARD

 

Aaron Seward