Investigation continues into WTC collapse.

As the rebuilding of the World Trade Center begins, the federal government's National Institute of Standards and Technology continues its 24-month investigation into the collapse of the Twin Towers and WTC 7.

In August 2002, the NIST began a $16 million investigation to study the factors contributing to the probable cause or causes of post-impact collapse of the buildings.

The latest development in the investigation is the release of the transcripts of emergency communications from the Port Authority of New York and New Jersey, said Michael E. Newman, NIST spokesman.

"The PA sent us about 1,000 hours of audio tapes from these conversations in March but we had only transcribed a small percentage of those," Newman said. "The transcripts from the PA will speed up the analysis of the communications greatly."

Although an NIST advisory committee met on the subject August 26-27, much more has yet to be investigated, he said.

"We have not come to any conclusions just more technological data has been gathered," Newman said. "We are also starting to interview survivors, first responders and victims' families."

The investigation also includes testing of the steel gathered from ground zero to determine the baseline performance of the buildings under wind and gravity loads; how much damage was done to the buildings, especially the floors and core, by the impact of the aircraft; determine how the steel responded to the high temperatures of the fires; and the most probable structural collapse sequence.

"What we found so far is that the quality of steel provided by suppliers is above or at quality than was required," Newman said. "Nothing we've seen so far indicates that the quality of steel contributed to the collapse, but we haven't made any conclusions yet."

The steel gathered is from all over the buildings to enable a complete study of the events, he said.

"We are fortunate to have gathered steel from the trusses, the columns, pieces from the core and the perimeter," Newman said. "We have enough material to get the job done. We even have a piece of one the columns of the North Tower that took the brunt of the impact."

The NIST is still awaiting information including original contract specifications for WTC towers; construction logs and maintenance logs for WTC 1, 2, 7; the 9/11 tapes and logs, transcripts of about 500 fast responders' interviews; contents of the aircraft that contributed to the fire; and the descriptions of partitions and furnishings in WTC 1, 2 and 7.

To be completed and ready for publication in September 2004, the study will include a fire safety research and development program to provide the technical basis for improved building and fire codes, standards, and practices; and a dissemination and technical assistance program to engage leaders of the construction and building community in implementing proposed changes to practices, standards-and codes. It also will provide practical guidance and tools to better prepare facility owners, contractors, architects, engineers, emergency responders, and regulatory authorities to respond to future disasters.