Partial List of Agencies, Organizations, and Experts

1,200 people who worked the flight 93 crash scene
40,000 people who worked the piles at Ground Zero
55 FBI Evidence Response Teams at Fresh Kills in New York
7,000+ FBI Agents
8,000+ people who worked the scene at the Pentagon
ACE Bermuda Insurance
AEMC Construction
AIG Insurance
Air Traffic Control System Command Center in Washington
Alexandria VA Fire & Rescue
Allianz Global Risks
American Airlines
American Concrete Institute
American Institute of Steel Construction
American Red Cross
Applied Biosystems Inc.
Applied Research Associates
Arlington County Emergency Medical Services
Arlington County Fire Department
Arlington County Sheriff's Department
Arlington VA Police Department
Armed Forces Institute of Pathology
Armed Forces Institute of Technology Federal Advisory Committee
ARUP USA
Atlantic Heydt Inc.
Bechtel
Berlin Fire Department
Big Apple Wrecking
Blanford & Co.
Bode Technology Group
Bovis Inc.
Building and Construction Trades Council
Bureau of Alcohol Tobacco and Firearms
C-130H crew in D.C. & Shanksville
Cal Berkeley Engineering Dept.
California Incident Management Team
Carter Burgess Engineering
Celera Genomics
Centers for Disease Control
Central City Fire Department
Central Intelligence Agency
Cleveland Airport control tower
Columbia University Department of Civil Engineering and Engineering Mechanics
Congressional Joint Intelligence Committee
Consolidated Edison Company
Construction Technologies Laboratory
Controlled Demolitions Inc.
Council on Tall Buildings and Urban Habitat
Counterterrorism and Security Group
CTL Engineering
D.H. Griffin Wrecking Co. Inc.
DeSimone Consulting Engineers
Dewhurst MacFarlane &Partners
DiSalvo Ericson Engineering
District of Columbia Fire & Rescue
DOD Honor Guard, Pentagon
D'Onofrio Construction
E-4B National Airborne Operations Center crews
Edwards and Kelcey Engineering
Engineering Systems, Inc.
Environmental protection Agency
Exponent Failure Analysis Associates
EYP Mission CriticalFacilities
Fairfax County Fire & Rescue
Falcon 20 crew in PA
Family members who received calls from victims on the planes
FBI Evidence Recovery Teams
Federal Aviation Administration
Federal Bureau of Investigation
Federal Emergency Management Agency
Federal Insurance Co.
FEMA 68-Person Urban Search and Rescue Teams: Arizona Task Force 1, California Task Force 1, California Task Force 3, California Task Force 7, Colorado Task Force 1, Fairfax Task Force 1, Florida Task Force 1, Florida Task Force 2, Maryland Task Force 1, Massachusetts Task Force 1, Metro Dade/Miami, Nebraska Task Force 1, New Mexico Task Force 1, New York Task Force 1, Pennsylvania Task Force 1, Tennessee Task Force 1, Texas Task Force 1, Utah Task Force 1, Virginia Task Force 1, Virginia Task Force 2, Washington Task Force 1
FEMA Disaster Field Office
FEMA Emergency Response Team
FEMA Urban Search and Rescue Incident Support Team-Advanced 3
Fire Department of New York
Fort Myer Fire Department
French Urban Search & Rescue Task Force
Friedens Volunteer Fire Department
Gateway Demolition
Gene Code Forensics
Georgia Tech Engineering Dept.
Gilsanz Murray Steficek LLP
GMAC Financing
Goldstein Associates Consulting Engineers
Guy Nordenson Associates
HAKS Engineers
Hampton-Clarke Inc.
HHS National Medical Response Team
HLW International Engineering
Hooversville Rescue Squad.
Hooversville Volunteer Fire Department
Hoy Structural Services
Hughes Associates, Inc
Hugo Neu Schnitzer East
hundreds of ironworkers, some of whom built the WTC
Hundreds of New York City Police Department Detectives
Industrial Risk Insurers
Institute for Civil Infrastructure Systems
International Association of Fire Chiefs
International Union of Operating Engineers Locals 14 & 15
J.R. Harris & Company
Karl Koch Steel Consulting Inc.
KCE Structural Engineers
Koch Skanska
Koutsoubis, Alonso Associates
Laboratory Corp. of America
Lamont-Doherty Earth Observatory
Leslie E. Robertson Associates
LIRo Engineering
Listie Volunteer Fire Company
Lockwood Consulting
M.G. McLaren Engineering
Masonry Society
Mazzocchi Wrecking Inc.
Metal Management Northeast
Metropolitan Airport Authority Fire Unit
Miami-Dade Urban Search & Rescue
Military District of Washington Search & Rescue Team
Montgomery County Fire & Rescue
Mueser Rutledge Consulting Engineers
Murray Engineering
Myriad Genetic Laboratories Inc.
National Center for Biotechnology Informatics
National Commission on Terrorist Attacks Upon the United States
National Council of Structural Engineers Associations
National Disaster Medical System
National Emergency Numbering Association
National Fire Protection Association
National Guard in D.C., New York, and Pennsylvania
National Institute of Standards and Technology (NIST)
National Institutes of Health Human Genome Research Institute
National Law Enforcement and Security Institute
National Military Command Center
National Reconnaissance Office
National Response Center
National Science Foundation Division of Civil and Mechanical Systems
National Security Agency
National Transportation Safety Board
National Wrecking
Natural Hazards Research and Applications Information Center
New Jersey State Police
New York City Department of Buildings WTC Task Force
New York City Department of Design and Construction
New York City Department of Environmental Protection
New York City Office of Emergency Management
New York City Office of the Chief Medical Examiner
New York City Police Department Aviation Unit
New York City Police Department Emergency Services Unit
New York Daily News
New York Flight Control Center
New York Newsday
New York Port Authority Construction Board
New York Port Authority Police
New York State Emergency Management Office
New York State Police Forensic Services
New York Times
North American Aerospace Defense Command
Northeast Air Defense Sector Commanders and crew
Numerous bomb-sniffing dogs
Numerous Forensic Anthropologists
Numerous Forensic Dentists
Numerous Forensic Pathologists
Numerous Forensic Radiologists
NuStats
Occupational Safety and Health Administration
Office of Emergency Preparedness
Office of Strategic Services
Orchid Cellmark
Parsons Brinckerhoff Engineering
Pennsylvania Department of Environmental Protection
Pennsylvania Department of Health and Human Services
Pennsylvania Region 13 Metropolitan Medical Response Group
Pennsylvania State Funeral Directors Association
Pennsylvania State Police
Pentagon Defense Protective Service
Pentagon Helicopter Crash Response Team
Pentagon Medical Staff
Pentagon Renovation Team
Phillips & Jordan, Inc.
Port of New York and New Jersey Authority
Pro-Safety Services
Protec
Public Entity Risk Institute
Purdue University Engineering Dept.
Robert Silman Associates Structural Engineers
Rolf Jensen & Associates, Inc
Rosenwasser/Grossman Consulting Engineers
Royal SunAlliance/Royal Indemnity
SACE Prime Power Assessment Teams
SACE Structural Safety Engineers and Debris Planning and Response Teams
Salvation Army Disaster Services
several EPA Hazmat Teams
several FBI Hazmat Teams
several Federal Disaster Medical Assistance Teams
several Federal Disaster Mortuary (DMORT) Teams
Severud Associates Consulting Engineers
Shanksville Volunteer Fire Company
Silverstein Properties
Simpson Gumpertz & Heger Engineers
Skidmore, Owings & Merrill LLP
Skilling Ward Magnusson Barkshire
Society of Fire Protection Engineers
Somerset Ambulance Association
Somerset County Coroner's Office
Somerset County Emergency Management Agency
Somerset Volunteer Fire Department
St. Paul/Travelers Insurance
State of Pennsylvania Emergency Management Agency
Stoystown Volunteer Fire Company
Structural Engineering Institute of the American Society of Civil Engineers (SEI/ASCE)
Structural Engineers Association of New York
Superstructures Engineering
Swiss Re America Insurance
Telephone operators who took calls from passengers in the hijacked planes
Teng & Associates
Thornton-Tomasetti Group, Inc.
TIG Insurance
Tokio Marine & Fire
Transportation Safety Administration
Tully Construction
Twin City Fire Insurance
Tylk Gustafson Reckers Wilson Andrews Engineering
U.S. Army Corps of Engineers
Underwriters Laboratories
Union Wrecking
United Airlines
United States Air National Guard
United States Fire Administration
United States Secret Service
United Steelworkers of America
University of Sheffield Fire Engineering Research
US Army Reserves of Virginia Beach Fairfax County and Montgomery County
US Army’s Communications-Electronics Command
US Department of Defense
US Department of Justice
US Department of State
Virginia Beach Fire Department
Virginia Department of Emergency Management
Virginia State Police
Vollmer Associates Engineers
Washington Post
Weeks Marine
Weidlinger Associates
Weiskopf & Pickworth Engineering
Westmoreland County Emergency Management Agency
Whitney Contracting
Willis Group Holdings
WJE Structural Engineers
Worcester Polytechnic Institute
World Trade Center security staff
XL Insurance
Yonkers Contracting
York International
Zurich Financial
Zurich Re Risk Engineering

Conspiracists: are these people liars, dupes, or shills?

Abolhassan Astaneh-Asl, Ph.D., P.E.
Alan Rosa, P.E., S.E.
Allyn Kilsheimer, P.E.
Amit Bandyopadhyay, S.E.
Amy Zelson Mundorff
Anamaria Bonilla, S.E.
Andrew McConnell, S.E.
Andrew Mueller-Lust, S.E.
Andrew Pontecorvo, P.E.
Anthony Kirk US&R Structural Specialist
Anthony W. Chuliver, S.E.
Antoine E. Naaman, Ph.D.
Antranig M. Ouzoonian, P.E.
Arlan Dobson, FEMA Region 2 DAS
August Domel, Ph.D., S.E., P.E.
Bernie Denke US&R Structural Specialist
Bill Cote
Bill Coulbourne, P.E., S.E.
Bob Gray (I.U.O.E.)
Bonnie Manley, P.E., S.E.
Boris Hayda, P.E., S.E.
Brian Lyons, Tully
Brian McElhatten, S.E.
Brian Smith (Col.), Chief Deputy Medical Examiner, Dover AFB
Charles Hirsch, M.D.
Charles J. Carter, AISC
Charles Thornton, P.E.
Charlie Vitchers
Christopher E. Marrion, P.E.
Christopher M. Hewitt, AISC
Chuck Guardia, S.E.
D. Stanton Korista, P.E., S.E.
Dan Doyle (IW 40)
Dan Eschenasy, P.E., S.E.
Dan Koch Jr.
Daniel A. Cuoco, P.E
Daniele Veneziano, P.E.
David Davidowitz, ConEd
David Hoy, S.E.
David Leach, USACE
David M. Parks, ME
David Peraza, P.E., S.E.
David Ranlet
David Schomburg
David Sharp, S.E.
David T. Biggs, P.E.
Dean Koutsoubis, S.E.
Dean Tills, P.E.
Delbert Boring, P.E.
Dennis Clark (IST)
Dennis Dirkmaat, Ph.D.
Dennis Mileti, Ph.D.
Dennis Smith
Dick Posthauer, S.E.
Donald Friedman, P.E.
Donald O. Dusenberry, P.E.
Ed McGinley, P.E.
Ed Plaugher, Chief, Arlington FD
Edward A. Flynn, Arlington Police Chief
Edward Depaola, S.E.
Edward M. DePaola, P.E.
Edward Stinnette, Chief, FCFD
Fahim Sadek, P.E., S.E.
Farid Alfawakhiri Ph.D.
FDNY Battalion Chief Frank Vallebuono
FDNY Captain Anthony Varriale
FDNY Chief Frank Cruthers
FDNY Chief Frank Fellini
FDNY Chief Joseph Callan
FDNY Chief of Operations Daniel Nigro
FDNY Deputy Chief Nick Visconti
FDNY Deputy Chief Peter Hayden
FDNY Firefighter Sam Melisi
Francis J. Lombardi, P.E.
Frank Gayle, Sc.D
Gary Keith, V.P. NFPA
Gary Steficek, S.E.
Gary Suson
Gary Tokle, Asst. VP, NFPA
George Tamaro, P.E., S.E.
Gerald Haynes, P.E.
Gerald Wellman US&R Structural Specialist
Guy Colonna, P.E., NFPA
Guylene Proulx, Ph.D.
H.S. Lew, P.E., S.E.
Hal Bidlack, Col. USAF (ret.)
Harold E. Nelson, P.E., FSFP.E.
Harry Martin, AISC
J. David Frost, Ph.D., P.E.
Jack Brown Deputy Chief Loudoun County (Va.) Fire Rescue Department
Jack Messagno, WTC project Manager (Tully)
James A. Rossberg, P.E.
James Chastain US&R Structural Specialist
James H. Fahey, S.E.
James Lord, FSFP.E.
James Milke, Ph.D., P.E.
Jan Szumanski, IUOE
Jason Averill, FSFP.E.
Jeffrey Hartman, S.E.
Jim Abadie, Bovis
Joel Meyerowitz
John Gross, Ph.D., P.E.
John Hodgens, FDNY (ret.)
John J. Zils, P.E., S.E.
John L. Gross, Ph.D., P.E.
John Lekstutis, P.E.
John M. Hanson, Ph.D, P.E.
John McArdle NYPD/ESU (DTC)
John Moran, NYPD/ESU (NTC)
John O'Connell
John Odermatt (NYC OEM)
John Ruddy, P.E., S.E.
John W. Fisher, P.E.
Jon Magnusson, P.E., S.E.
John Ryan, PAPD
Jonathan Barnett, Ph.D
Joo-Eun Lee P.E., S.E.
Joseph C. Gehlen, P.E., S.E.
Jozef Van Dyck, P.E.
Juan Paulo Morla, S.E.
Karl Koch III
Karl Koch IV
Kaspar Willam, P.E., S.E.
Kenneth Holden
Kent Watts
Kevin Brennan, OSHA
Kevin Malley, FDNY (ret.)
Kevin Terry, S.E.
Kurt Gustafson, P.E., S.E.
Larry Keating (IW 40)
Lawrence C. Bank, Ph.D., P.E.
Lawrence Griffis, P.E.
Leo J. Titus, P.E.
Leonard M. Joseph, P.E.
Leslie E. Robertson, P.E., S.E.
Long T. Phan, Ph.D., P.E.
Lou Mendes, P.E., S.E.
Louis Errichiello, S.E.
Manny Velivasakis, P.E.
Mark Blair
Mark Kucera, USACE
Mark Tamaro, P.E
Mark Volpe, IW 40
Marty Corcoran
Matthew G. Yerkey, P.E., S.E.
Merle E. Brander, P.E.
Mete A. Sozen, Ph.D., S.E.
Michael Burton, P.E.
Michael Dallal
Michael Hessheimer, S.E.
Michael Tylk, P.E., S.E.
Mike Banker, FDNY Capt. (SOC)
Mike Marscio, P.E.
Miroslav Sulc,, P.E., S.E.
Mohammed Ettouney
Morgan Hurley, FSFP.E.
Nestor Iwankiw, Ph.D., P.E.
Nick Carcich
Norman Groner, Ph.D.
Pablo Lopez, P.E., S.E.
Paul A. Bosela, Ph.D., P.E.
Paul F. Mlakar, Ph.D., P.E.
Paul Sledzik
Paul Tertell, P.E.
Pete Bakersky
Peter Chipchase, S.E.
Peter Rinaldi, P.E.
Pia Hoffman
Rajani Nair, S.E.
Ramon Gilsanz, P.E., S.E
Randy Lawson
Raul Maestre, P.E., S.E.
Raymond F. Messer, P.E.
Reidar Bjorhovde, Ph.D., P.E
Richard Bukowski P.E., FSFP.E.
Richard G. Gewain, P.E., S.E.
Richard Gann, Ph.D.
Richard Garlock, P.E., S.E.
Richard Kahler US&R Structural Specialist
Robert C. Sinn, P.E., S.E.
Robert F. Duval (NFPA)
Robert Frances US&R Structural Specialist
Robert J. McNamara, P.E., S.E.
Robert Ratay, Ph.D., P.E., S.E.
Robert Shaler, M.D.
Robert Smilowitz, Ph.D., P.E
Robert Solomon, P.E.
Robert Wills, AISC
Ronald Hamburger, P.E., S.E.
Ronald J. LaMere, P.E.
Ronald Rehm, Ph.D.
Ronald Spadafora, FDNY D.A.C
Ruben M. Zallen, P.E.
Russell "Rusty" Dodge Jr, Asst. Chief, Fort Belvoir FD
S. Shyam Sunder, P.E., S.E.
Saw-Teen See, P.E.
Shankar Nair. P.E., S.E.
Shawn Kelly, Arlington County Fire Marshal
Socrates Ioannides, P.E., S.E.
Sonny Scarff
Stan Murphy, P.E.
Stephen Cauffman
Steve Rasweiler, FDNY B.C. (SOC)
Stuart Foltz, P.E.
Terry Sullivan, Bovis
Theodore Galambos, P.E.
Theodore Krauthammer, Ph.D., P.E.
Therese P. McAllister, Ph.D., P.E.
Thomas Hawkins Jr, Chief, AFD
Thomas Schlafly, AISC
Todd Ude, P.E., S.E.
Tom Scarangello, P.E.
Tom Stanton (IST)
Tony Beale, P.E.
Valentine Junker
Venkatesh Kodur, Ph.D., P.E.
Victor Hare, P.E.
Vincent Dunn, FDNY (ret.)
W. Gene Corley, Ph.D., P.E., S.E.
W. Lee Evey
Wallace Miller
William Baker, P.E., S.E
William Grosshandler, Ph.D., ME
William McGuire, P.E.
Willie Quinlan, IW
Zdenek Bazant, Ph.D., S.E.

9/11 Commission & Staff
Thomas H. Kean, Chair
Lee H. Hamilton, Vice Chair
Richard Ben-Veniste
Fred F. Fielding
Jamie S. Gorelick
Slade Gorton
Bob Kerrey
John F. Lehman
Timothy J. Roemer
James R. Thompson

Joanne Accolla
Alexis Albion
Scott Allan
John Azzarello
Caroline Barnes
Warren Bass
Ann Bennett
Mark Bittinger
Madeleine Blot
Antwion Blount
Geoff Brown
Daniel Byman
Dianna Campagna
Sam Caspersen
Melissa Coffey
Lance Cole
Marquittia Coleman
Marco Cordero
Raj De Counsel
George Delgrosso
Gerald L. Dillingham
Thomas Dowling
Steven Dunne
Thomas Eldridge
John Farmer
Alvin Felzenberg
Gordon England
Lorry Fenner
Susan Ginsburg
T. Graham Giusti
Nicole Grandrimo
Doug Greenburg
Barbara Grewe
Elinore Hartz
Len Hawley
Christine Healey
Karen Heitkotter
Walt Hempel
Michael Hurley
Dana Hyde
Michael Jacobson
Bonnie Jenkins
Reginald Johnson
William Johnstone
Stephanie Kaplan
Miles Kara
Janice Kephart-Roberts
Hyon Kim
Christopher Kojm
Katarzyna (Kasia) Kozaczuk
Gordon Lederman
Daniel Leopold
Sarah Linden
Douglas MacEachin
Daniel Marcus
Ernest May
James Miller
Kelly Moore
Charles Pereira
John Raidt
John Roth
Peter Rundlet
Lloyd Salvetti
Kevin Scheid
Kevin Shaeffer
Tracy Shycoff
Dietrich Snell
Jonathan Stull
Lisa Sullivan
John Tamm
Cate Taylor
Yoel Tobin
Emily Walker
Garth Wermter
Serena Wille
Philip Zelikow, Executive Director

The Congressional Joint Inquiry on 9/11
Senate Members

Bob Graham, D - Florida, Chairman
Richard C. Shelby, R - Alabama, Vice Chairman
Carl Levin
Jon Kyl
John D. Rockefeller
James M. Inhofe
Dianne Feinstein
Orrin Hatch
Ron Wyden
Pat Roberts
Richard J. Durbin,
Mike DeWine
EvanBayh
Fred Thompson
John Edwards
Richard Lugar
Barbara Mikulski
Al Cumming, Staff Director
William Duhnke, Minority Staff Director

House Members
Porter J. Goss, Chairman
Nancy Pelosi
Doug Bereuter
Sanford D. Bishop
Michael N. Castle,
Jane Harman
Sherwood L. Boehlert
Gary A. Condit
Jim Gibbons
Tim Roemer
Ray LaHood
Silvestre Reyes
Randy Cunningham
Leonard L. Boswell
Peter Hoekstra,
Collin C. Peterson
Richard Burr
Bud Cramer
Saxby Chambliss
Terry Everett
Timothy R. Sample, Staff Director
Michael W. Sheehy, Democratic Counsel

Staff
Eleanor Hill
Rick Cinquegrana
David Barton
Ann Bennett
Daniel Byman
Michael Davidson
George Ellard
Rahul Gupta
Kay Holt
John Ivicic
Michael Jacobson
Everette Jordan
Miles Kara
John Keefe
Thomas Kelley
Dana Lesemann
Patti Litman
Arthur Menna
Lewis Moon
Patricia Ravalgi
Alonzo Robertson
Robert Rosenwald
Michael Smith
Catherine Williams

A few details to flesh out the numbers

...The federal presence was much larger in New York, as well. A dizzying blur of acronym soup arrived to help: CDC, FAA, FBI, HHS and dozens more. At the height of the federal response, there were a total of 6,547 federal employees, including 1,544 from FEMA and its US&R task forces, supporting operations in New York and Virginia. Of the 27 available FEMA US&R teams, more than 20 eventually rotated through New York, representing a total of 1,240 firefighters and 80 search dogs. As many as eight teams at a time operated in New York. http://firechief.com/mag/firefighting_first_respondersfeds_join/
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In the aftermath of the 9/11 attacks, the FBI's response was immediate. In a matter of hours we had deployed to each of the crash sites, ordered dozens of seasoned management personnel back to Washington, and fully staffed a 24/7 operation at our Command Center with up to 500 persons representing approximately 30 federal agencies. At the height of the 9/11 investigation, known as PENTTBOM, the FBI assigned 7,000 agents to assist full-time. The majority were reassigned from other national security and criminal investigative work. The lack of prior counterterroism training and experience, although not recognized by the OIG, needs to be factored into this discussion. ...Meanwhile, PENTTBOM became the largest and most complex investigation in the history of the FBI. In spite of operating under severe handicaps, the New York Office - relocated to a garage on 26th street, and lacking a proficient infrastructure - began a 24/7 operation utilizing 300 investigators from 37 agencies. The 1-800 toll-free line set up in our Atlanta office received 180,000 calls from a shocked public eager to assist. 225,000 e-mails were received on the FBI's internet site. Evidence response teams from throughout the country were dispatched to New York, Washington and Pittsburgh. Nationwide we covered over 500,000 investigative leads and conducted over 167,000 interviews. We collected over 7,500 pieces of evidence which were submitted for analysis. Working in conjunction with New York City agencies and authorities, we helped process over 1.8 million tons of debris for investigative leads and victim identification and took more than 45,000 crime scene photographs. http://www.fas.org/irp/congress/2003_hr/062503rolince.html
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Approximately 7,000 FBI Employees Were Redirected in Early Weeks. At its peak, approximately 6,000 Special Agents were working on the investigation with assistance from support staff. Additional resources were dedicated to the related threats and tragedies such as the anthrax investigation, Olympics security, the Richard Reid investigation, and the Daniel Pearl kidnapping. New FBI Investigative Groups Were Created. The Financial Review Group, Document Exploitation Group, and E-Mail Exploitation Group were all created since September 11th. In addition, the Telephone Applications Group as well as the Threat, Warning, Analysis and Dissemination Groups were both expanded. http://www.fas.org/irp/news/2002/05/fbireorganizationfactsheet.pdf
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At least 449 responding organizations in New York City. Over 8,000 people given security clearance to work at Pentagon crash site Good look at Arlington County, Virginia (Pentagon) first responder organizational structure http://dels.nas.edu/dr/docs/harrald.pdf
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Flight 93: Shanksville At Shanksville, which was by far the smallest of the three 9/11 crash scenes, over 1,100 people from 74 agencies and organizations worked at the scene. On 9/11 alone, these included: • 8 Police Departments • 7 EMS Services • 8 Fire Departments • 10 Emergency Management Agencies • NTSB • ATF • FBI • CISM • Red Cross • United AirlinesSource: PowerPoint presentation by Rick Lohr, Director of Somerset County Emergency Management Agency. Download it here as a PDF http://wtc7lies.googlepages.com/SomersetCountyEmergencyManagementAge.pdf
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In addition to the estimated 10,000 Fire Department of New York (FDNY) personnel, an estimated 30,000 other workers and volunteers potentially were exposed to numerous psychological stressors, environmental toxins, and other physical hazards. http://www.cdc.gov/MMWR/preview/mmwrhtml/mm5335a1.htm
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Because of ongoing fire activity and the large numbers of civilians and rescue workers who were killed during the attacks, approximately 11,000 FDNY firefighters and many emergency medical service (EMS) personnel worked on or directly adjacent to the rubble and incurred substantial exposures. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12238534&dopt=Abstract
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OSHA calculates that in over 3.7 million work hours, only 57 non-life threatening injuries were recorded at the WTC site. http://www.pdhealth.mil/library/downloads/The%20Occupational%20Safety%20and%20Health%20Admin istration%20Response.pdf
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You’re dealing with a work scene that, in the first week or two, had probably two to three thousand, if not more, emergency responders on the scene. Pretty much 24 hours a day. All of them with various backgrounds and training. You had construction workers, you had heavy-equipment operators, you had medical workers, firefighters, police officers, hygienists, military personnel. All of them with different levels of training, different types of equipment. So you had to try and logistically bring in all of the equipment for these people. You’re bringing in multiple manufacturers and vendors. —Firefighter-special operations panel member http://www.rand.org/pubs/conf_proceedings/CF176/CF176.ch2.pdf
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Fresh Kills Crime Scene Info * The site covered 175 acres. * 24 local, state, and federal agencies participated, with as many as 1,000 workers a day * 17,000 tons of material were processed daily. * 55 FBI Evidence Response Teams worked the site -- over 1,000 agents -- plus FBI medics, safety officers, and other specialists. * New York Evidence Response Team members worked over 8,000 hours at the site, at the morgue, and at Ground Zero -- and one, Special Agent Gerry Fornino, personally worked over 1,818 hours at the vehicle recovery operation with the Port Authority and NYPD. Source: http://www.fbi.gov/page2/nov03/nyhs112703.htm
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Number of U.S. Customs Agency Volunteers working search and inspection at Fresh Kills Landfill: at least 193 http://www.cbp.gov/xp/CustomsToday/2002/March/custoday_location.xml
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from RECOVERY: THE WORLD TRADE CENTER RECOVERY OPERATION AT FRESH KILLS (PDF of Traveling Exhibit) The exhibition chronicles the quiet history after September 11. The days at Fresh Kills ended as discreetly as they began. Debris removal at Ground Zero ended on June 28, 2002. The sorting at Fresh Kills officially ended on July 2 at 1:02 p.m. Recovered from the 1.8 million tons of material inspected: 4,257 human remains helped bring closure to hundreds of families; 54,000 personal items and 4,000 photographs, many returned to their owners; 1,358 personal and departmental vehicles; and thousands of tons of steel. The numbers are difficult to process, but these images begin to tell the story. The Police, FBI, City Sanitation workers, and the thousands who worked there made history “on the hill.” The hill that overlooks downtown Manhattan where the towers once stood is now changed forever – Mark Schaming Director of Exhibitions and Programs New York State Museum Above exhibit thanks to these organizations working at Fresh Kills: The New York Police Department The New York Fire Department The Federal Bureau of Investigation New York City Department of Sanitation Phillips and Jordan, Inc. The Fresh Kills Incident Commander, NYPD Inspector James Luongo, Lt. Bruce Bovino, FBI Special Agents Richard Marx and Gerry Fornino, the FBI Evidence Response Team, the NYPD Recovery Team, the Port Authority Police Department, NYC Department of Sanitation, and all the people from the World Trade Center Recovery Operation
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U.S. Army Corps of Engineers receives Fresh Kills debris management contract http://sept11.wasteage.com/ar/waste_fema_assigns_fresh/index.htm
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400 FBI Agents working at Fresh Kills (and some taking souvenirs?) http://www.msnbc.msn.com/id/4373627/
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As you know, on September 11, 2001, Special Agents of the Federal Bureau of Investigation (FBI) and New York Police Department (NYPD) detectives were dispatched to the Fresh Kills Landfill on Staten Island, New York to process the debris of the World Trade Center (WTC) for physical evidence and human remains. This recovery effort, the largest and longest in the FBI's history, resulted in 1.8 million tons of debris being collected and examined by twenty-four federal, state, and local agencies. On September 12, 2001, I was designated to lead and coordinate this effort as an Evidence Response Team (ERT) Leader. This operation ceased in August 2002. –Richard B. Marx, Special Agent http://www.ussartf.org/news.htm Engineer salvage yard visits for steel inspection As of March 15, 2002, a total of 131 engineer visits had been made to these yards on 57 separate days. An engineer visit typically ranged from a few hours to an entire day at a salvage yard. The duration of the visits, number of visits per yard, and the dates the yards were visited varied, depending on the volume of steel being processed, the potential significance of the steel pieces being found, salvage yard activities, weather, and other factors. Sixty-two engineer trips were made to Jersey City, 38 to Keasbey, 15 to Fresh Kills, and 16 to Newark. Three trips made in October included several ASCE engineers. Eleven engineer trips were made in November, 41 in December, 43 in January, 28 in February, and 5 through March 15, 2002. Source: FEMA WTC report, Appendix D
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Pentagon Overview Local responders arrived immediately, and other agencies, including five USAR teams, came to assist. The Arlington County Fire Department set up an incident command system and coordinated the emergency response. The rescue and recovery phase lasted 11 days, after which Arlington County transferred responsibility for the incident and site management to the Federal Bureau of Investigation (FBI), on September 21. No esponders were killed. Demolition of the damaged area began on October 18 and was completed on November 29. Reconstruction of the damaged area is expected to be completed in Spring 2003. http://www.rand.org/pubs/conf_proceedings/CF176/CF176.ch2.pdf
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Good study of response and (partial) list of organizations responding to the Pentagon attack Observing and Do http://www.gwu.edu/%7Eicdrm/publications/nsf911/response.htmlcumenting the Inter-Organizational Response to the September 11th Attack on The Pentagon
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October 1, 2001 U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES personnel assigned

Source: http://www.emergency.com/2001/11sep01-terror.htm

TOTAL PERSONNEL Emergency Operations Center (EOC): Rockville, MD 20 New York City 594 FEMA Response Headquarters: Washington, DC 11 FBI Command: Washington, DC 2 Regional Operations Centers (I, II, III, IV): Various 9

TOTAL 636

New York City PERSONNEL: NEW YORK CITY Management Support Team (MST): Sheraton Hotel 49 DMAT: TOTAL 172 DMAT: Four Clinics 102 DMAT: Management and Support 40| DMAT: Staging 30 Presbyterian Hospital Burn Center 14 Centers for Disease Control (CDC)- Epidemiologists 40 CDC, Other 16 Veterinary Medical Assistance Team (VMAT) 14 DMORT: TOTAL 260

DMORT: New York City Medical Examiners Office (NYCME) 146 DMORT: Management & Marriott 9 DMORT: Family Assistance Center (United and American Airlines Site) 1 DMORT: FAC (Pier 94) 5 DMORT: Ground Zero 15 DMORT: Landfill 6 DMORT: Processing Data Information - Pier 92 56 Disaster Portable Morgue Unit (DPMU) Staff 6 Disaster Portable Morgue Unit (DPMU) DMORT West Reception Area 16 DMORT: Staging N/A CCRF Mental Health 7 Mental Health 9 Pharmacists Staging 2 Specialty: CCRF Forensic Dentists 6 Department of Veterans' Affairs: Various Other Assistance and Support 5 TOTAL :594

Clinical Data (Past 24 hours / Total) Human Patients Treated 161 / 5,735 Animal Patients Treated by VMAT for acute symptoms 14 / 893

Recovered Remains as reported by the State of New York: 0800 hours, September 29 Remains 4,735 Identified 214

The Management Support Team (MST) established in New York City is located at a hotel at 7th Avenue and 52nd Street. There continues to be daily-in and out-processing of personnel. The next rotation of DMAT teams is in process.

Inter-Departmental Cooperation

The Department of Health and Human Services (HHS), Office of Emergency Preparedness (OEP), continues to work in cooperation with their partners in the National Disaster Medical System (NDMS). The Department of Veterans' Affairs (VA) is providing support to the city through its New York City VA health care facilities as well as through Emergency Support Function (ESF) #8, Health and Medical Services, of the Federal Response Plan. Under the Federal Response Plan, through ESF # 8, VA has deployed 2 burn nurses to the Cornell University Medical Center Burn Unit; a radiology technician to the scene of the plane crash in Western Pennsylvania; and an emergency manager to the USPHS/EOC. Two emergency managers are on duty at the ESF 8 Management Support Team (MST) in NYC. A clinical psychologist at the Oklahoma City VAMC was requested by the American Red Cross National Headquarters to travel to Washington, DC and provide consultation on CISM. In the aftermath of the attack, the VA Manhattan received and treated a total of 76 victims with an additional 17 treated at the VAMC Brooklyn, three at the VAMC in the Bronx and two at the Northport VAMC for a total of 98. VA received two additional mission assignments from the HHS/United State Public Health Service (USPHS), lead agent for ESF # 8 (Health and Medical Services) for the Federal Response Plan (FRP). One stress counselor is assisting the deployed mental health teams to provide support to federal workers in New York City (NYC). Five (5) VA emergency managers began working with the Management Support Team (MST) in NYC on Monday, October 1, 2001.

The Federal Emergency Management Agency (FEMA) provides leadership in all aspects of the rescue mission and liaison officers.

The Department of Defense deployed the USNS Comfort to New York City. The 250-bed USNS Comfort arrived at Pier 92 on September 14 and departed on October 1, 2001. It was used as a rest facility for responders and served hundreds of rescue personnel daily. DoD provided liaison officers to several federal entities agencies and departments.

Epidemiologists The epidemiologists from CDC were deployed by request of Secretary Thompson and are assisting the New York City Department of Health, to determine any patterns of later developing ailments caused by the terrorist attacks. They are taking daily data analyses at New York City hospitals. Over 35,000 medical charts have been reviewed. Staffing levels and schedules will be developed to accommodate the times of greatest need in the hospitals. Ongoing surveillance both in New York City and Washington, DC, has not indicated any anomalies to date.

Most of the Urban Search and Rescue (USAR) teams have been deactivated by the Federal Emergency Management Agency (FEMA). Currently only one USAR team remains in New York City. DMAT and DMORT will assess how that decision impacts on their missions in New York City over the coming days.

DMAT There are currently four operating clinics all within two blocks of the World Trade Center (WTC) site. They are operational in the four sectors around ground zero. DMAT rotations are progressing according to schedule. Fourteen burn nurses are deployed to provide staffing relief for critical patients at the NY Presbyterian Hospital Burn Center. A plan for demobilization of the nurses at the end of the mission is being developed. The demobilization is expected to occur on October 14. According to the New York State Department of Health sufficient quantities of vaccines are available and air and water quality have been tested and meet or surpass existing standards.

DMORT personnel are on duty at the World Trade Center site, the City Medical Examiner's Office, the United Airlines and American Airlines Family Assistance Center (FAC), and the FAC at Pier 94 and the Staten Island Landfill. DMORT-FAC personnel are currently conducting family interviews, collecting records, and performing other administrative duties. DMORT personnel are in the process of expanding the site at the Landfill on Staten Island. Much of the material from the World Trade Center site is being shipped there. DMORT personnel are on site to review the wreckage being brought to the site. DMORT personnel are providing 24-hour support to the city Medical Examiner. Their duties include: data entry, morgue activities, photo/scanning, supervisors, and liaison officers. Operations in the Medical Examiner's Office will increase as the recovery continues.

USNS Comfort The 250-bed USNS Comfort left for their homeport on October 1, 2001.

VMAT Veterinary Medical Assistance Teams are operating veterinary clinics in New York City. They are caring for the search dogs assisting with the search and recovery mission. They are also providing care for the federal search and recovery dogs and to non-federal search dogs on site. VMAT personnel at Staten Island have been reassigned temporarily until after a meeting with the New York City Office of Emergency Management on the status of resuming that operation.

NMRT-E The National Medical Response Team-Weapons of Mass Destruction- EAST (NMRT-E) is a specialized response force sponsored by the U.S. Public Health Service that is designed to provide medical care following a nuclear, biological, and/or chemical incident. They are specially trained to work towards decontamination of sites, and can provide medical care in contaminated areas if needed. As of September 17, NMRT-E, in New York City, was deactivated and returned to North Carolina.

Mental Health Ten Federal mental health personnel are on site serving the mental health needs of federal responders (SAMHSA, CCRF, and VA personnel). Mental Health Assistance Team (MHAT) personnel have established a plan to rotate in new personnel and demobilize existing personnel. Mental health needs will be continually assessed throughout the deployment. Substance Abuse and Mental Health Services Administration (SAMHSA) personnel are currently coordinating operations at four sites for mental health counseling. They continue to provide mental health care to many of the responders every day. Mental health personnel also provide an orientation as well as debriefing for DMAT and DMORT members arriving and department New > York City. Over the past 24 hours 70 mental health contacts were made, bringing the mission total to 2,553 contacts.

PENNSYLVANIA There has been no change since SITREP #19. As of September 26, the DMORT operation in Somerset County, Pennsylvania, has been completed. Most DMORT personnel have returned home, some have been redeployed to New York City as needed. Prior to closing operations, a 100% record audit was completed. Victim DNA is being processed to confirm identities.

THE PENTAGON There has been no change since SITREP #19 Immediately following the incident, the NMRT-DC was deployed to the Pentagon to assist with the recovery mission. The 36-member NMRT was assisting with washing-down workers returning from the site. They were working 2-12 hour shifts of 18 people, washing down approximately between 800-1,000 workers every 24 hours. In addition, NMRT washed down equipment and dogs leaving the site. The NMRT-DC and MST were demobilized on September 26, 2001.


A NATION CHALLENGED: THE TRADE CENTER; TOWERS' COLLAPSE RAISES NEW DOUBTS ABOUT FIRE TESTS

A NATION CHALLENGED: THE TRADE CENTER; TOWERS' COLLAPSE RAISES NEW DOUBTS ABOUT FIRE TESTS


Published: April 8, 2002

The fiery collapse of three World Trade Center skyscrapers has led scientists, engineers and building officials to question the century-old practice of relying on tests done in hulking, low-tech furnaces to determine if building materials will survive out-of-control blazes.

The furnace tests, conducted at places like Underwriters Laboratories here, focus on the ability of separate building components -- a steel column or a concrete roof support -- to survive temperatures as high as 2,000 degrees.

The test has many defenders, but many scientists say that even before Sept. 11, they had concluded that the furnace tests were out of touch with a computer-age understanding of the devastation caused by the fury of a real fire. At least when it comes to buildings, that research shows, the whole often acts differently from a simple-minded sum of the parts.

The super-baked, seared furnaces here are the seething heart of the most trusted and advanced testing laboratory in the United States for building structures, materials and products. But within those same furnaces, Underwriters and other labs are using testing methods that have changed little since they were devised when the first Model T Fords were rolling off the assembly lines.

A 12-foot steel-and-masonry door slides shut, closing off a brick-lined furnace, its red-painted exterior corroding around a maze of pipes, flanges and valve handles. Inside, a vertical steel column is braced with concrete supports, a web of wires and sensors strung between its surface and the furnace wall like clotheslines. A worker lights a kerosene-soaked rag wrapped around the end of a steel bar and shoves it through a small window in the door, igniting 70 yellow billowing flames that lick the column. Within three minutes, the temperature has shot past 1,000 degrees and is still rising.

The test is on, and its fidelity is anything but an academic issue. This and similar tests shape what amounts to the DNA of the nation's infrastructure, what goes into every commercial and large residential building.

The basic test of the fire-resisting capabilities of fireproofing, steel supports and concrete structures -- a furnace procedure called ASTM E-119 -- has many proponents who say that the declining number of fire deaths in the United States since the mid-1970's proves its effectiveness.

But critics call it unrealistic, primitive, even medieval. And other countries, including England, Australia, New Zealand, Sweden and Japan, have modified fire standards and codes to allow designers to use 21st-century computer tools to custom design buildings to withstand unusual or intense fires not anticipated by the traditional regulations.

Tests in this country do not, for example, account for plastic and synthetic combustible materials, which were unknown in the 1910's when the ''standard fire'' used in the test was developed. Nor does the test try to mimic how a real fire sweeps through rooms in a building, creating structural stresses in one place that can lead to failures elsewhere in the building's interconnected skeleton. Within the cramped furnace, the test involves individual beams or columns and does not even check whether, once mounted in a building, the bolted, welded or riveted connections between them are equally resistant to failure in a fire.

''No one who is in the business with any type of technical background believes there is any kind of strong correspondence, in any way, between the performance test and a real fire,'' said Kathleen Almand, a structural engineer who is executive director of the Society of Fire Protection Engineers.

None of those engineers and scientists, and certainly not Ms. Almand, have suggested that shortcomings in the test led to the collapse of the twin towers and 7 World Trade Center, a 47-story skyscraper that burned and collapsed under mysterious circumstances late on Sept. 11.

No modern high-rise had ever completely collapsed in a fire before that day, a fact that along with the steadily decreasing fire death rate has reassured building officials and engineers that the furnace tests, whatever their technical failings, do pretty well in winnowing out dangerous or inadequate materials and structures. But as research and computer modeling of fires advanced in recent decades, scientists and engineers have become acutely aware that the furnace blasts were more fantasy flame than accurate road test of conditions in a burning building. The same researchers say they are concerned that recently developed construction materials like lightweight, high-strength concrete and composites could survive furnace tests but be prone to complex failures.

''If I say, 'That product passed the test,' you as John Q. Public may be happy,'' said Dr. James G. Quintiere, a professor in fire protection engineering at the University of Maryland. ''But if we say, 'It passed the test, but we don't know how it will function in your house,' you would not be happy.''


The Science of Fire

Even before Sept. 11, about 20 percent of firefighters who died in building fires were killed in localized collapses of one kind or another. So fire experts say a true scientific understanding of how fires affect large structures could help determine when it is too dangerous for firefighters to be in a burning building.

Dr. Shyam Sunder, a division chief at the Building and Fire Research Laboratory of the National Institute of Standards and Technology, said that developing the science of fire beyond the furnace tests could save lives and have an impact in at least three broad areas: restoring public confidence in tall buildings, protecting firefighters and other emergency personnel and improving safety for building occupants.

The institute, which does research and provides the technical basis for standards but does not impose regulations, is planning to undertake a $16 million follow-up investigation on the trade center disaster after a federal inquiry, led by the Federal Emergency Management Agency and the American Society of Civil Engineers, releases its own report in late April or early May.

The institute has also begun a wider research and development effort with the goal of improving building and fire codes and engineering practices for structures of all kinds.

If the institute's work is successful, Dr. Sunder said, ''we'll have the tools for engineers to design and retrofit for fire safety.''

''Fire and emergency service personnel will have a better understanding of the performance to be expected from buildings,'' he added.

A draft of the FEMA report, which has been obtained by The New York Times, has already placed a sharp focus on the ASTM E-119 test, though the report is careful not to imply that the test is somehow responsible for the collapses. The test ''does not provide tools to determine how long a building component can expect to perform in an actual fire,'' the report says.

An Oversized Barbecue

At the Underwriters Laboratory campus in this northern Chicago suburb, where workers carry out those blazing tests in a yawning building reminiscent of an airplane hangar, forklifts shuttle back and forth, moving huge columns, while cranes suspended from overhead rails slowly lift giant sections of roof into the furnaces and technicians mill about in front of a forest of dials, gauges and controls.

Three huge furnaces, each in a separate corner of the hangar, are designed to handle three different tests: one for steel columns, one for wall assemblies, and one for ceilings and floors. Little about the setup is high-tech.

''Do you need the torch, Bill?'' Eckhard Brodde, an assistant, yelled to the foreman, Bill Joy, as the two prepared the cube-shaped furnace for testing columns last week.

''Let's close the door first,'' Mr. Joy yelled back. Both gave it a heavy push. ''It is not moving,'' Mr. Joy said, before an extra shove was applied. ''There you go,'' he said, as the door clicked into place.

As if lighting an oversized barbecue, Mr. Joy sets fire to a kerosene-soaked rag and sticks it through a small opening in the furnace. ''Three, two, one -- gas on,'' he shouts, as the flames burst into life.

With this inferno of flames racing from dozens of gas jets, these workers are determining just how long the steel column and its fireproofing can hold up under this thermal assault.

The result is a fire rating, expressed in hours, for this column, and eventually for countless different components that make up a building, from sections of roofing to walls for emergency exit stairways to assemblies of glass, brick and plaster that make up a building facade. A column might be given a ''two-hour'' rating, meaning that it has withstood two hours in the furnace at temperatures that research done in the 1910's determined to be typical of office fires of the day.

A history book on U.L.'s testing procedures, published in the mid-1920's and on display in a glass case at a company museum here, describes the procedure Mr. Joy and Mr. Brodde are following, almost as if it were written yesterday.

''The furnace itself is a box of thick masonry, and is heated by four rows of blast burners,'' the book says. ''On the outside of the walls are valves, through which it is possible to control the distribution and intensity of the fire.''

Just as in the 1910's and 1920's, an organization called the American Society for Testing and Materials, or ASTM International, specifies exactly how those tests are done. Ultimately these ratings are incorporated into local and state regulations, or fire codes, which dictate minimum standards for each of the thousands of components in a building.

A Comprehensive Approach

The proponents of using modern science are advocating an extremely different approach using a comprehensive evaluation of how an entire building reacts -- and perhaps fails -- in a fire.

The computer models for that sort of evaluation are still under development, and they would still require fire tests, although much more sophisticated ones intended to yield a full scientific understanding of how fire sweeps through a building and, sometimes, brings it down.

This approach, for example, might identify a critical connection between beams and columns that could become the weakest link in a major fire and therefore has to have much stronger fire protection. It might also find ways for developers to cut costs by reducing insulation where it is less needed.

But any change is likely to come slowly, particularly because furnace tests received little scrutiny outside government research institutes and university labs before Sept. 11. The furnace test ''will tell you if a product does work or doesn't work,'' said Neil Schultz, executive director of VTEC Laboratories in the Bronx. ''You can have all the computer models in the world and they wouldn't tell you that.''

But even at places like Underwriters Labs, ASTM International and the government agencies where fire codes for cities including New York are written, technicians and officials say they are ready to consider the new philosophy.

''Irrespective of 9/11 and the World Trade Center, I think the fire science, the sophistication level, and the understanding is such that the momentum has started to look at these things more precisely,'' said Arthur E. Cote, chief engineer at the National Fire Association, an organization that helps develop codes.

''The sort of inevitable march,'' he added, ''is ongoing. The pace will depend on economics and the reward from the effort.''

World Trade Center puzzle lingers

Workers clear the site of the World Trade Center, AP
Investigations began as the wreckage was cleared
Better construction could have saved hundreds of lives in the World Trade Center (WTC), but investigators are still puzzling over the evidence.

The WTC towers "did very well" to stand as long as they did, the head of the official inquiry into their collapse said in a BBC Horizon programme broadcast in the UK on Thursday.

But other structural engineers say use of more robust materials would have definitely allowed some people trapped on the upper floors of the centre to escape and may have prevented their collapse entirely.

The issue is of vital interest because the WTC's design was revolutionary and its construction methods influenced skyscrapers across the world.

Designed for impact

Leslie Robertson designed the structural elements of the WTC towers to withstand the impact of the largest airliner then in service, the Boeing 707.


Would they ultimately have collapsed? Maybe not

Charles Thornton
Structural engineer
"With the 707 however, to the best of my knowledge, the fuel load was not considered in the design," he told Horizon.

But as the programme explained, it was the fuel aboard the hijacked Boeing 767s that led to the towers' collapse.

Each tower had a strong central column and a strong external steel skeleton.

Bound to fall

But neither could ever be strong enough to stand by itself, so the key to stability was the steel floor trusses which linked the two.

Investigators believe that foam fireproofing surrounding these trusses blew away when the planes hit the towers, leaving the steel to buckle in the heat of the fires that followed.

Once the crucial trusses began to fail, the towers were bound to fall.

In the minutes that they remained standing, most of the people below the levels where the planes hit were able to escape.

But those above were trapped as fire blocked the central columns and their stairways.

Only four people from either tower managed to escape from the levels above the impacts.

Squeegee escape

Some investigators believe that better fireproofing of the central columns would have saved hundreds of them, even if the towers had still collapsed in the end.

The drywall fireproofing surrounding the central columns was highly fire-resistant but not very strong.

Researchers believe much of it was dislodged on impact.

And it was weak enough for a man trapped between floors in a lift to hack his way through it with the squeegee he used for cleaning windows.

Gene Corley, head of the official inquiry into the towers' collapse, says that the towers did well not to fall down immediately.


I cannot escape the people who died there

Leslie Robertson
WTC structural engineer
"The fact that one of them lasted 55 minutes and the other about an hour and 40 minutes says they did very well," he told the programme.

Mr Corley is due to publish his interim findings in April.

But other engineers appearing in the programme speculate that a better tower design could have survived.

"Had the floor system been a more robust floor system with much stronger connections between the exterior and the inside, I think the buildings... would have lasted longer," said Charles Thornton.

"Would they ultimately have collapsed? Maybe not."

Mr Robertson is plagued by the wisdom of hindsight and deeply distressed by the memory of what happened to those inside his buildings.

"I cannot escape the people who died there... that still to me somehow up there in the air are burning.

"I cannot make that go away," he said.

Twin Towers showed 'remarkable' resistance

World Trade Center remains
The towers' survival "astonished" engineers
The World Trade Center showed "remarkable" resistance in the 11 September attacks and its design contributed to saving many lives, a US government report has found.

Wreckage from World Trade Center
The Towers could have survived the impact had fire not broken out

The report, jointly issued by the Federal Emergency Management Agency and the American Society of Civil Engineers, found that the length of time the buildings remained upright after being hit by two passenger planes "astonished most observers, including knowledgeable structural engineers".

It claimed this resistance was testament to its good construction and undoubtedly saved the lives of many within the buildings.

"The fact that the structures were able to sustain this level of damage and remain standing for an extended period of time is remarkable and is the reason that most building occupants were able to evacuate safely," the report said.

Immense heat

Investigators believe the WTC would probably even have survived being hit by two passenger jets on 11 September had fires not weakened the buildings' support structures.

Firefighters and rescue workers help those injured shortly after the attacks
Up to 3,000 people died in the attack on the World Trade Center

The report said engineers now believe that it was a combination of three factors: the force of the aircraft impacts, the heat from burning jet fuel, and the heat from the burning of much of the buildings' contents that caused the towers to collapse.

But most crucially, the team of civil, structural and fire protection engineers found that building fire systems in general are not equipped to deal with simultaneous fires breaking out over an entire building, as happened at the Twin Towers, Reuters news agency reported.

The report found that heat from the many fires ignited in the minutes immediately following the planes hitting the buildings rapidly became equivalent in temperature to "the power produced by a large commercial power generating station".

Designers exonerated

This heat gradually induced additional stresses into the already damaged structural frames while simultaneously softening and weakening them, it said.

The resulting damage then inevitably led to the collapse of both structures.

The findings also exonerated the buildings' designers, stating that many of the structural and fire protection procedures in place in the buildings were "superior" to other constructions.

However it also warned that it may not be "technically feasible" to design a building that could withstand the force of a plane hitting it and, even if possible, the costs would be prohibitive.

Up to 3,000 people are thought to have died in the Twin Towers attack.

Twin Towers 'never fire-tested'

World Trade Center is struck on 11 September
A two-year study is investigating the towers' collapse

The floors of the World Trade Center had not been tested for their ability to withstand fire, an interim report has found.

Extreme heat generated by the many fires that broke out after two aircraft were flown into the buildings on 11 September is seen as one potential factor in their collapse.

The government agency that built the towers never tested the fireproofing insulation on the WTC's floors - meant to withstand two hours of fire - according to the National Institute of Standards and Technology.

Arden Bement, NIST director, said the report did not draw conclusions or make recommendations.

"That's for later, when we have a much more complete picture," he said.

The NIST's two-year investigation was launched last year, and will analyse the collapse and evacuation of the WTC in an effort to make buildings safer in the future.

Despite the widely accepted notion that no skyscraper could have withstood a fuel-laden jet slicing into its core, relatives say there are still many technical questions to be answered.

Fire-proofing upgraded

Previous reports have found that the towers showed "remarkable resilience", standing for more than an hour after being hit by the aircraft.

But some experts say the buildings may even have withstood the strikes, had fires not weakened their support structures.

In 1999, the building's owners, the Port Authority of New York and New Jersey, issued guidelines to upgrade the fireproofing by tripling the thickness on the flooring.

As recently as 2000, officials were still redoing the fireproofing, noting in one property assessment that some areas could withstand only one hour in a fire.

By 11 September 2001, the NIST report found, fireproofing had been upgraded on 29 floors in the areas of the towers where the hijacked planes struck.

Glenn Corbett, a US fire science expert, was quoted by AP saying that the upgraded system should have been tested.

But the fast-moving fires in the towers on 11 September may have been far more severe than the typical conditions assumed in the fire resistance test, he added.

9/11 demolition theory challenged

South tower of New York's World Trade Center collapses after attacks on 11 September 2001. Image: AP
The study analysed how the twin towers collapsed
An analysis of the World Trade Center collapse has challenged a conspiracy theory surrounding the 9/11 attacks.

The study by a Cambridge University, UK, engineer demonstrates that once the collapse of the twin towers began, it was destined to be rapid and total.

One of many conspiracy theories proposes that the buildings came down in a manner consistent with a "controlled demolition".

The new data shows this is not needed to explain the way the towers fell.

Over 2,800 people were killed in the devastating attacks on New York.

After reviewing television footage of the Trade Center's destruction, engineers had proposed the idea of "progressive collapse" to explain the way the twin towers disintegrated on 11 September 2001.

This mode of structural failure describes the way the building fell straight down rather than toppling, with each successive floor crushing the one beneath (an effect called "pancaking").

Resistance to collapse

Dr Keith Seffen set out to test mathematically whether this chain reaction really could explain what happened in Lower Manhattan six years ago. The findings are published in the Journal of Engineering Mechanics.

Previous studies have tended to focus on the initial stages of collapse, showing that there was an initial, localised failure around the aircraft impact zones, and that this probably led to the progressive collapse of both structures.

Man stands amid rubble of the World Trade Center, AFP/Getty
Once the collapse began, it was destined to be "rapid and total"
In other words, the damaged parts of the tower were bound to fall down, but it was not clear why the undamaged building should have offered little resistance to these falling parts.

"The initiation part has been quantified by many people; but no one had put numbers on the progressive collapse," Dr Seffen told the BBC News website.

Dr Seffen was able to calculate the "residual capacity" of the undamaged building: that is, simply speaking, the ability of the undamaged structure to resist or comply with collapse.

His calculations suggest the residual capacity of the north and south towers was limited, and that once the collapse was set in motion, it would take only nine seconds for the building to go down.

This is just a little longer than a free-falling coin, dropped from the top of either tower, would take to reach the ground.

'Fair assumption'

The University of Cambridge engineer said his results therefore suggested progressive collapse was "a fair assumption in terms of how the building fell".

"One thing that confounded engineers was how falling parts of the structure ploughed through undamaged building beneath and brought the towers down so quickly," said Dr Seffen.

The south tower of the World Trade Center collapses, AP
Conspiracy theorists see evidence of a "controlled detonation"
He added that his calculations showed this was a "very ordinary thing to happen" and that no other intervention, such as explosive charges laid inside the building, was needed to explain the behaviour of the buildings.

The controlled detonation idea, espoused on several internet websites, asserts that the manner of collapse is consistent with synchronised rows of explosives going off inside the World Trade Center.

This would have generated a demolition wave that explained the speed, uniformity and similarity between the collapses of both towers.

Conspiracy theorists assert that these explosive "squibs" can actually be seen going off in photos and video footage of the collapse. These appear as ejections of gas and debris from the sides of the building, well below the descending rubble.

Other observers say this could be explained by debris falling down lift shafts and impacting on lower floors during the collapse.

Dr Seffen's research could help inform future building design.

 
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