35W design flaw prompts bridge reviews
ST. PAUL - A design error in the Minneapolis bridge that collapsed Aug. 1 prompted Minnesota officials to look at the original plans of 59 similar bridges.
The $500,000 re-evaluation follows Tuesday's preliminary report blaming gusset plates that connect bridge beams for the Interstate 35W bridge collapse.
Bridges Minnesota officials gave priority status for the re-evaluation include U.S. 61 over Mississippi River at Hastings, U.S. 63 over Mississippi River at Red Wing and the Blatnik Bridge in Duluth. Bridges throughout the state will be examined.
State transportation officials said inspectors most likely will not have to physically examine most of the bridges, but consultants will re-evaluate their design to make sure they were properly designed. Bridges whose design is being examined were built anywhere from 1889 to 1987.
Of the state bridges being re-evaluated, 23 are on state roads and 36 are on local roads. In some cases, the re-evaluation already has begun. Pawlenty said the work will be completed in June; some reports will be available as early as April.
It is the second round of checks for some Minnesota bridges since the Aug. 1 collapse. On Aug. 2, Pawlenty ordered all 13,000 bridges in Minnesota to undergo special inspections.
Nearly 4,000 state brides underwent the inspections. The 843 worse local bridges were inspected, but local officials did not have to follow Pawlenty's order and some did not conduct special inspections.
No problems were found in the 56 bridges similar to the one that collapsed, but State Bridge Engineer Dan Dorgan said problems such as occurred on the 35W bridge would not have been discovered during an inspection.
Chairman Mark Rosenker of the National Transportation Safety Board said in Washington that some 35W gusset plates were too thin for the 35W bridge; they were a half-inch thick instead of an inch like they should have been.
Dorgan said gusset plates generally are the strongest part of a bridge and inspectors don't look at their thickness once a bridge is built. However, he said, had a re-evaluation like now is being done on the 56 bridges been done on the 35W structure, the problem would have been discovered.
The problem was in the bridge's design, Rosenker said, and there is no evidence other bridges have the same problem.
However, the NTSB recommends that similar bridges be re-evaluated before undergoing major changes. Minnesota Gov. Tim Pawlenty went an extra step and ordered all similar bridges to be re-evaluated immediately.
"The design process led to a serious error," Rosenker told a news conference. "The bridge inspections would not have identified the error in the design of the gusset plates."
The Aug. 1 collapse, near downtown Minneapolis, killed 13 and injured more than 100.
Tuesday's report was preliminary. The NTSB will take several more months to complete its investigation.
Pawlenty did not wait for a final federal report later this year. He said Minnesotans need assurances their bridges are safe.
The Republican governor, who has been under attack by Democrats who hint he was to blame for the collapse because he vetoed transportation funding increases, urged everyone to stop jumping to conclusions about who is to blame and wait until the final federal report is released later this year.
If the federal preliminary report holds, placing blame may be difficult. Mathematical calculations made during the bridge's design in the 1960s cannot be found, so investigators cannot determine why the gusset plates were too thin.
Among state highway bridges being re-evaluated are:
-- Minnesota 19, over Sulpher Lake, Redwood County, Honner Township.
-- U.S. Business 2, over Red River, East Grand Forks.
-- Minnesota 40, over Lac Qui Parle Lake, Chippewa County, Kragero Township.
-- Minnesota 123, over Kettle River, Sandstone.
-- Minnesota 317, over Red River, Marshall County, Fork Township.
-- U.S. 61, over Mississippi River, Hastings.
-- Minnesota 11, over Red River, Kittson County, Teien Township.
-- Blatnik Bridge, over St. Louis River, Duluth.
-- U.S. 63, over Mississippi River, Red Wing.
-- U.S. 2, over Red River, East Grand Forks.
-- Minnesota 1, over Red River, Oslo.
-- Minnesota 7, over Chippewa River, Montevideo.
-- Minnesota 72, over Rainy River Lake, Baudette.
-- Minnesota 210, over St. Louis River, Thomson.
-- Minnesota 60, over Mississippi River, Wabasha.
-- U.S. 53, over Rainy River, International Falls.
Among local bridges being re-evaluated are:
-- Township 220, over Chippewa River, Chippewa County, Big Bend Township.
-- State park road, over Baptism River, Lake County, Beaver Bay Township.
-- Township 25, over Pomme De Terre River, Swift County, Moyer Township.
-- County A9, over Yellow Medicine River, Yellow Medicine County, Wood Lake Township.
-- Township 127, over Belle Creek, Goodhue County, Vasa Township.
-- County 1, over Red River, Polk County, Hubbard Township.
-- County 1, over Big Fork River, Koochiching County.
-- County 2, over Zumbro River, Wabasha County, Oakwood Township.
-- County 9, over Red River, Polk County, Tynsid Township.
-- County 7, over Zumbro River, Wabasha County, Mazeppa Township.
-- County 36, over Red River, Clay County, Georgetown Township.
-- County 25, over Red River, Norman County, Hendrum Township.
-- County 7, over Red River, Polk County, Vineland Township.
-- County 7, over Cloquet River, St. Louis County, Industrial Township.
-- County 931, over Sturgeon River, St. Louis County, Sturgeon Township.
-- County 17, over Minnesota River, Redwood County, Delhi Township.
-- Township 362, over North Fork Crow River, Meeker County, Kingston Township.
-- Township 676, over West Lost Lake, Otter Tail County, Maine Township.
-- Township 166, over Cannon River, Dakota County, Waterford.
-- City 58, over Cannon River, Cannon Falls.
MnDOT official Bob McFarlin said the NTSB had discussed the gusset problem as early as August, so his department began looking into other bridges with similar designs then.
A state bridge in St. Cloud already has been found clear of gusset problems and work on bridges in Hastings, Winona, St. Peter, Red Wing, Duluth and Grand Forks is starting now.
McFarlin - standing in for Transportation Commissioner Carol Molnau, who was meeting with congressmen in Washington, D.C. - said he thinks the state can compel local governments to complete re-evaluations similar to those the state is conducting.
Dorgan said bridge designers in the 1960s as well as now would submit their designs to a colleague, who would make sure the original designer did everything right.
Other Minnesota bridges were designed by the same firm that drew up the 35W bridge plans, including the one at Hastings.
Dorgan said "there may be a small measure of relief" finding out that no one now in MnDOT could be blamed for the collapse, but Pawlenty said the incident remains a sad and tragic affair.
The new evaluations are good, Dorgan said, because in Minnesota "we have a higher level of concern." There was no indication other states were following Minnesota's lead and re-evaluating so many bridge designs.
The bridge engineer said that Minnesotans should not be concerned about bridge safety. There is no reason to believe any of the other bridges have the same gusset flaw the 35W bridge did.
The U.S. 61 bridge at Hastings, built in 1950, already is being re-evaluated, state officials said. Its report should be ready by April, when major repair work - scheduled before the Aug. 1 collapse - is to begin.
Minnesota's busiest two-lane bridge is an example of why bridges are not safe, two state senators said Tuesday.
Sen. Katie Sieben, DFL-Cottage Grove, said the bridge was rated as in worse shape than the Interstate 35W bridge that collapsed in Minneapolis Aug. 1. But the earliest it would be replaced would be in 10 years, Senate Transportation Chairman Steve Murphy, DFL-Red Wing, said.
The senators reacted to a just-released report indicating the bridge may have serious problems - in bearings needed to keep the bridge flexible and a load rating that may be higher than the bridge can handle.
An inspection report completed in August but only released this week also suggests inspectors take a close look at cracks in weld, replace obsolete bearings and replace leaking expansion joint seals. Inspectors also noted there was too much corrosion on the bridge.
MnDOT officials said the bridge's 40-ton limit is appropriate, even though the inspection report said materials in the bridge have become thinner and no load study has been made for eight years.
"The load limit definitely should be changed," Murphy said, and on bridges other than the U.S. 61 structure, too.
Murphy and Sieben said despite their displeasure with MnDOT leaders, they feel if lawmakers appropriated more transportation money the Hastings bridge would be replaced sooner than planned.
However, Murphy bristled at the suggestion that legislators earmark money just for the bridge.
"We don't earmark projects," Murphy said. "We're not going to play that game and we are not going to let the governor play that game."
Lawmakers generally give MnDOT money without listing specific projects where it must be spent. The Hastings bridge is listed as being replaced between 2018 and 2022 on the state's priority list.
"If MnDOT had appropriate levels of funding, the Hastings bridge would be accelerated," Murphy said.
The chairman also said Lt. Gov. Carol Molnau, also Gov. Tim Pawlenty's transportation commissioner, should resign. He said current plans are for the Senate to decide whether to confirm her this year, and indications are that she does not have the votes to keep her job.
Minnesota needs $1.8 billion to fix state bridges and another $450 million for local ones, Murphy said.