National Transportation Safety Board
Office of Public Affairs
Washington, D.C. -- In a report adopted today, the National Transportation Safety Board determined that poor construction planning and execution led to the failure of a temporary bracing system for a bridge girder being installed above Interstate 70 (I-70) in Golden, Colorado, causing the girder to collapse onto a passenger vehicle on I-70, killing three people. The Board cited as contributing factors the lack of uniform, consistent bracing standards and the Colorado Department of Transportation's (CDOT's) narrow definition of falsework, which did not include lateral bracing. Also contributing to the accident was CDOT's failure to effectively oversee safety critical contract work.
"This accident shows us just how important it is to have very clear guidelines about what is required for safe operations," stated NTSB Acting Chairman Mark V. Rosenker, "Sometimes it seems like such common sense that we wonder why we need these guidelines, and then we see an accident like this one."
On the morning of May 15, 2004, a steel girder that had been installed about 3 days earlier and secured with a temporary bracing system, sagged into the eastbound lanes of I-70 and struck a sport utility vehicle traveling along the roadway. All three people in the vehicle, including a 2-year-old child, were killed in the accident.
The girder had been installed as part of a bridge-widening project managed by CDOT. To perform the construction work, CDOT contracted with Asphalt Specialties, Inc., which subcontracted the girder installation to Ridge Erection Company, Inc.
Ridge's girder installation and bracing plan was inadequate and was not prepared or reviewed by a Registered Professional Engineer, nor was it required to be. The lack of planning resulted in multiple problems for the Ridge crew during the construction process carried out on the night of May 11 to 12. The crew did not have the proper tools, and it inadvertently began installing a section of the accident girder backward. These situations delayed the projected work for that night, so Ridge did not complete the work intended for that night and had to secure the girder with a temporary bracing system, expecting to complete the girder installation work the next night. However, due to weather, this work was postponed, so the girder remained secured with the temporary bracing system for several days.
While constructing the temporary bracing system, Ridge had experienced difficulty anchoring the bracing to the severely degraded bridge deck pavement. Postaccident examination also revealed that Ridge had installed the girder out of plumb. The braces, originally intended to secure a correctly installed girder for hours rather than days, failed causing the girder to sag into the roadway.
As a result of its investigation, the Board recommended that the Federal Highway Administration, the Occupational Safety and Health Administration (OSHA), and the American Association of State Highway and Transportation Officials (AASHTO) work together to develop consistent guidance and requirements for constructing such temporary highway bracing and related structures, known as "falsework," including that all falsework plans should be prepared or approved by a Registered Professional Engineer.
The Board also cited CDOT's failure to oversee safety-critical portions of the project because CDOT's on-site supervisors were aware of the problems Ridge experienced but did not question the adequacy of the work done by the subcontractor. The Board recommended that AASHTO revise its guidance concerning oversight conducted by highway supervisory construction personnel to call for prequalification of subcontractors; submission of engineer-approved written plans for all construction, including falsework; intervention when contractors or subcontractors demonstrate a lack of competence; and monitoring of temporary bracing systems until construction is completed.
A synopsis of the Board's report, including the probable cause and recommendations, is available on the Board's website, www.ntsb.gov. The Board's full report will be available on the website in several weeks.
NTSB Office of Public Affairs: (202) 314-6100
The National Transportation Safety Board (NTSB) is an independent federal agency charged with determining the probable cause
of transportation accidents, promoting transportation safety, and assisting victims of transportation accidents and their families.