Minnesota Pioneer Press: Thirteen years of inspections offer the deepest look into the bridge's cond
Thursday, January 3, 2008
Thirteen years of inspections offer the deepest look into the bridge's condition
Cracked welds. Loose bolts. Parts of the bridge literally being eaten away by the elements.
A Pioneer Press review of 13 years of in-depth inspection reports for the Interstate 35W bridge revealed an accumulation of problems that lingered as inspectors hustled to the next bridge. Federal law requires states to inspect bridges, but it doesn't require states to actually fix them - that's left to the judgment of state bridge engineers and the policymakers who approve money to do the work. Interactive Map of Bridge Inspections
"The problem is there, year after year after year. And they don't let you do anything about it," said Bart Andersen, a Minnesota Department of Transportation bridge inspector who took a leave of absence earlier this year to act as a union representative.
As investigators continue to piece through the wreckage to determine what caused the Minneapolis span to fall during the evening rush hour Aug. 1, killing 13 and injuring more than 100, the detailed annual reports provide perhaps the deepest look into the bridge's condition.
Among the reports' findings:
- Rust had gotten so bad in places that when repairs were finally considered, they weren't possible.
- A bearing system showed no recent signs of movement in one pier, meaning the bridge couldn't expand and contract as designed for Minnesota's harsh weather.
- Missing bolts often were not replaced for years, if at all.
But spray paint reported by motorists was addressed quickly.
"Graffiti is a high priority, because it is a public complaint," Andersen said.
Despite federal funding for bridges and federal mandates for inspections, how bridges are fixed is largely left to individual states. MnDOT's inspection manual says immediate repairs might be necessary if an inspection rating system shows serious deterioration, but when and how to fix a bridge is often more art than science.
"Ultimately, it's the state's bridge," said John Schadl, a spokesman for U.S. House Transportation Chairman Jim Oberstar, D-Minn., who has proposed strengthening the National Bridge Inspection Standards. "It's probably not the best arrangement for the government to impose regulations on state-owned property."
Oberstar's bill would not mandate repairs if inspectors find problems.
Rust was allowed to worsen. Strip seals in joints in the bridge's roadway meant to protect from water and corrosive road salts had pulled away. By the time MnDOT got around to replacing them, the metal tabs that held the seals in place were so rusted that new seals couldn't be installed.
The Pioneer Press review of the documents shows rust was spotted in many locations, particularly where exposed to the elements - under the median between the northbound and southbound lanes and under the expansion joints where the seals had pulled out. The rust and corrosion were so bad in places that steel joints were pushed apart.
Warnings went unheeded. A 1993 inspection noted a bent brace. Two years later, an inspector wrote, "CHECK THIS!!!!!!!!" Two years after that, someone finally did - it apparently was bent during construction.
A 1999 inspection suggested any loose or missing stringer bolts should be documented and replaced. But loose bolts in the truss over the west bank pier were reported year after year - apparently without being fixed .
Safeguards probably were not functioning. Inspectors also checked the bridge's rusted bearings, which are designed to allow steel to expand and contract with changes in temperature. Most bearings appeared to be functioning, but the bearing at Pier 6 on the Mississippi River's west bank showed no signs of movement. If the bridge isn't allowed to expand, critical parts are likely to come under severe strain in extreme temperatures.
MnDOT officials have said they did everything to monitor the bridge and keep it in working order - including spending millions of dollars on engineering studies. The agency's leaders also urge the public to wait until completion of a National Transportation Safety Board investigation before drawing conclusions about the cause of the collapse.
The NTSB is reviewing bridge-inspection reports as part of its investigation, which is not expected to conclude until next fall.