Collapse of Towers Tied to Fireproofing, Probe Says (Update1) By Peter Young and David M. Levitt April 5 (Bloomberg) -- The World Trade Center towers in New York collapsed because the impact of hijacked jets dislodged fireproofing on core steel columns that then weakened in the ensuing blaze, U.S. government investigators said today. The report by the National Institute of Standards and Technology said the death toll in the Sept. 11, 2001, terrorist attacks that killed 2,749 people could have been as high as 14,000 if the buildings had been fully occupied at the time. The findings will be used to make recommendations for revised building and fire codes, standards and practices used as models across the U.S., said S. Shyam Sunder, the lead investigator for the institute, a Gaithersburg, Maryland-based unit of the U.S. Commerce Department. ``The buildings would likely not have collapsed under the combined effects of aircraft impact and the subsequent jet-fuel ignited, multifloor fires, if the fireproofing had not been dislodged'' by the impact of the crash, the report said. The condition and thickness of the fireproofing ``did not play a significant role'' in the collapse of the twin towers, investigators said, while leaving in question the material's ability to adhere to the steel structure. While today's findings are subject to review, they represent ``late-stage'' conclusions likely to appear in the final version in June, NIST spokesman Michael Newman said. The institute, whose mission includes developing office- building safety standards, is three years into an investigation of the attacks on the 110-story twin towers in lower Manhattan by Osama bin Laden's al-Qaeda terrorist network. Tallest Buildings The twin towers, the tallest buildings in New York City, were hit by virtually identical Boeing 767 jetliners commandeered by the terrorists. One World Trade Center, the north tower topped by a television mast, was struck at 8:47 a.m. between the 93rd and 99th floors and collapsed after 102 minutes. Two World Trade Center, the south tower, was struck between the 77th and 85th floors at 9:03 a.m. and collapsed after 56 minutes. Both buildings were rocked by the impact of the crashes. World Trade Center 2 swayed more than 20 inches at the rooftop, and continued shaking for more than four minutes, the report said. In addition to dislodging the fireproofing, the impact caused all except two of 198 elevators in the towers to stop functioning, forcing people to flee by way of stairs, some of which were blocked or inaccessible, the report said. About 17,400 people were in the two towers at the time of the attacks, about one-third of their capacity, the report said. Had the buildings been full, evacuation would have required about four hours, it said. ``The egress capacity required by current building codes and practice is based on a `phased' evacuation strategy, not `full' evacuation,'' the report noted. `Successful' Evacuation Still, ``87 percent of the WTC tower occupants, including more than 99 percent of those below the floors of impact, were able to evacuate successfully,'' the report said. Two-thirds of those who survived had participated in a fire drill in the 12 months preceding Sept. 11, and 93 percent of those participants ``were instructed about the location of the nearest stairwell,'' the report said. Many people were ``unprepared for the physical challenge of full building evacuation,'' with ``numerous occupants'' requiring rest breaks during the descent or turning ``to elevators after finding the stairwells strenuous,'' the report said. Monica Gabrielle, wife of Sept. 11 victim Richard Gabrielle and co-chairperson of the Skyscraper Safety Campaign, criticized today's report. ``Both NIST and the 9-11 Commission keep saying they're on a fact-finding, not fault-finding mission,'' she said in an interview. ``What we think is, without accountability, you're not going to have true reform.'' Chunks `Missing' Contradicting today's report, Gabrielle maintains that fireproofing was missing from some steel sections before the attack. ``We have pictures of huge chunks missing from normal wear and tear and sway of the building,'' she said. ``Unfortunately the forensic evidence is gone.'' The Port Authority of New York and New Jersey, which owned the trade center, studied the impact of a Boeing 707 flying at 600 miles per hour and crashing into the 80th floor of one of the towers, during their design in 1964. The planners did not consider the effect of subsequent fires, the report said. ``Buildings are not specifically designed to withstand the impact of fuel-laden commercial airliners,'' the report noted, adding, ``Building codes do not require building designs to consider aircraft impact.'' To contact the reporters on this story: Peter Young in New York at pyoung13@bloomberg.net ; David M. Levitt in New York at dlevitt@bloomberg.net . Last Updated: April 5, 2005 14:44 EDT