White washing the i-35W bridge collapse: though it fell almost four years ago, questions still remain about the exact causes of the tragedy--and the National Transportation Safety Board's report has clone little to provide real answers for the worried public.
ON AUG. 1, 2007, the I-35W Bridge collapsed during rush hour, killing 13 people, injuring 145, and bringing massive economic disruption to the Twin Cities area. The November 2008 National Transportation Safety Board (NTSB) report, which followed 15 months of investigation, advised the public and transportation officials around the country that the bridge collapse was a one-time occurrence, caused by a design error that had gone undetected at the time of construction. In short, the collapse was a one-off from which no lessons could be learned to avoid future failures. That simply is not the case, as there is a desperate need for reform in the way we fund and maintain the nation's infrastructure.
NTSB tellingly ignored a host of critical factors that were not disclosed to the public or other state bridge operators, thus delegitimizing the efficacy of the report, which masked far more than it revealed about how the bridge was maintained, funded, and operated. NTSB claims that the bridge's collapse was the result of the under-design of certain gusset plates (metal plates used to connect structural members of a truss and hold them in position at a joint) at six nodes of the deck truss. These should have been an inch thick but, instead, were only half that.
Adding to the stresses on the too-thin gusset plates, the report states, were increases to the bridge's load. According to the NTSB, had all the gusset plates met design standards at the time of construction, then--even with the increased weight from the bridge's additions, the increase in traffic, and the weight of the construction materials and machinery--the collapse would not have occurred.
The reality is that the NTSB's findings virtually ignored 16 years of inspections by the Minnesota Department of Transportation that reflected the steady decline of the bridge. Widespread evidence of corrosion for critical steel members, frozen bearings that locked the structure in place, and cracks throughout the bridge and approach spans rendered its condition "poor," requiting that some of its Waffle lanes to be closed.
All of these critical factors were highlighted in several outside engineering reports commissioned by the Minnesota DOT. These reports, which detailed the frailties of this fracture-critical bridge--meaning the failure of one structural member would trigger the collapse of the bridge--made a series of recommendations, which went completely unheeded, for addressing the problems resulting from neglected maintenance.
The NTSB report wrongly exonerates the Minnesota DOT. Based on the maintenance history of the I-35W Bridge's extensive wear and tear, corrosion, and signs of incipient failure for many years prior to its collapse, dismissing the DOT of any responsibility for its collapse is inexcusable. Inspections dating back to 2001 identified widespread corrosion and fatigue caused by weather and traffic volume. Recognizing the fragility of the bridge's original fracture-critical design, engineering firm consultants stressed the need for added redundancy to strengthen the bridge. A June 2006 inspection--the last one before the collapse--found cracking and fatigue problems and gave the structure a sufficiency rating of 50%. A rating of 50% or lower pursuant to Federal standards is interpreted to mean that the bridge should be considered for replacement.
The NTSB reported none of these facts. It dismissed any connection between the bridge's collapse and the DOT's maintenance, or its poor condition for a decade and a half prior to its failure. The report said nothing about the DOT's decisionmaking process or whether it had acted prudently in light of the engineering consultants' recommendations to protect the well-documented fragility of the bridge.
The NTSB's findings were subjected to criticism even before they were published. After Chairman Mark Rosenker made a preliminary announcement concerning the design of the gusset plates, Rep. James Oberstar (D.-Minn.)--chairman of the House Committee on Transportation and Infrastructure, who promptly had introduced a bill to overhaul national bridge inspection procedures following the I-35W disaster-angrily accused the NTSB of rushing to judgment. Right after that, in the Minneapolis-St. Paul Star Tribune, Jim Carlson, a member of the Minnesota legislature's joint committee on the I-35W Bridge collapse, wrote, "The collapse was not an act of God; it was an error of oversight. Something was missed."
The NTSB report obviously was influenced by politics. On Aug. 14, 2007, the Minnesota legislature appointed a joint committee to investigate the bridge collapse, which hired the law firm Gray Plant Mooty to produce its own report.
Months later, Rosenker appeared at a press conference. Although in his opening statement he was careful to say that, "We have not yet determined the probable cause of the accident," he went on to call 16 underdesigned gusset plates the "critical factor that began the process of this collapse." This statement earned him a sharp rebuke from Oberstar, who wrote in a letter to Rosenker that, "Such announcements undermine the process and create the potential for committing the Board to conclusions which will be difficult to change if subsequent investigation suggests other possible conclusions."
Rosenker retracted his statements, but found himself at loggerheads with Oberstar again after the NTSB announced that it would not hold an interim public hearing on the collapse. The three NTSB members--all Republicans--who voted against holding an interim public hearing explained their decision by stating that the NTSB staff feared that, by doing so, time and resources would be taken away from their investigation. Oberstar and the two Democratic members of the NTSB (who issued a dissent from the majority's decision) replied by arguing that performing a thorough and trustworthy investigation was more important than speed. It was no small matter that the head of the Minnesota DOT was Gov. Tim Pawlenty's lieutenant governor, Carol Molnau, who herself was not an engineer experienced in infrastructure management.
The politics surrounding the NTSB investigation certainly provide much fodder for speculation as to the possible motivation of the board's leadership and findings, but it does not require a political orientation to observe that the NTSB report has significant flaws, including errors of apparent neglect or omission as well as of technical understanding.
The NTSB report wrongly places blame on the engineers. The reality is that there has been a mass exodus of engineers out of the public sector. It is likely that the lack of engineers, not the decades-old design of the bridge, contributed to its collapse. The Gray Plant Mooty report pointed to various organizational weaknesses within the DOT that compromised the safety of the bridge: a poor flow of information; bad use of expert advice; and an organizational structure that impeded the maintenance process.
The inadequate flow of information within the DOT was related to the loss of engineering personnel. Placing the primary blame for a failure of this magnitude on engineers was an attack on the profession as a whole. Yet, the American Society of Civil Engineers, the largest professional engineering association in the country, has marshaled no protests and has conducted no investigations of its own to challenge this indictment of individual engineers who no longer are around to defend themselves.
The NTSB report does not mention the bridge's rested bearings. A June 2006 Minnesota DOT inspection noted surface rest corrosion and pack rust connected with the unsound condition of 15% of the paint; numerous problems with the main truss members, including poor weld details, section loss, and flaking rest; and a variety of problems with the floor beam masses, stringers, truss beating assemblies, and other components.
While the NTSB findings on the cause of the collapse made no reference to the condition of the bridge bearings, frozen by years of rest, they may have played a contributory role in the collapse. The DOT's inspection reports acknowledge that the I-35W Bridge's members were bent or misaligned, and that critical bearings had been rested and frozen in place, preventing movement. All of these signs of deterioration should have required close scrutiny, but that never happened.
In reality, the likely cause of the collapse was triggered by a weakness in one of the bottom chords of the design masses, a finding that appears to have been identified separately by the structural engineering specialists retained by the attorneys for many of the plaintiffs in the civil action against the bridge's contractors and engineers.
What is most important to note about the role of the NTSB is that it failed to serve as a clearinghouse to alert all other state bridge operators about the lessons that should have been learned from this collapse. There still are 7,980 bridges in the nation that are structurally deficient and fracture-critical, each of which is in danger of suffering the same fate as the I-35W span.
To have failed to identify the true causes of the collapse is one notable failure of this governmental agency, but to have ignored the lessons that should be alerting the other 49 stales that their citizens, too, are in jeopardy of suffering the same tragic fate is inexcusable. The risks of continuing to pay no heed to our N-maintained national infrastructure are almost unimaginable. This discussion must turn into a dialogue at every level of government and policymaking. No less than our future national security and ability to retain our global leadership status are at stake.
Barry B. LePatner, founder of the New York-based law firm LePatner & Associates LLP, is the author of Too Big to Fall: America's Failing Infrastructure and the Way Forward and Broken Buildings, Busted Budgets: How to Fix America's Trillion-Dollar Construction Industry, as well as the coauthor of Structural and Foundation Failures.
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|Author:||Lepatner, Barry B.|
|Publication:||USA Today (Magazine)|
|Date:||May 1, 2011|
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