A look at how bridge maintenance and inspections compare at city, county and state levels
It’s not something anyone wants to dwell on, especially bridge engineers. The collapse of the Interstate 35W bridge last August apparently hasn’t meant sweeping changes in the way bridges are inspected in Minneapolis. However, state-owned, fracture-critical bridges must now be inspected annually. With the arrival of nicer weather, inspection crews may become more visible around the city’s 650 bridges. Every inspector goes through similar training. What differs among city, county and state crews are the sheer quantity and quality of bridges they inspect. That, and how they are funded.
The following shows how city, county and state compare when it comes to the inspections process.
Minneapolis’ Bridge Maintenance and Inspection Unit (BMIU), which consists of only three inspectors, performs inspections of every one of the 382 city-owned bridges each year. As of 2005, the average age of city-owned bridges was 60, said Bridge Maintenance Engineer Jeff Johnson. That is expected to go down with the replacement of the Camden Avenue Bridge in northwest Minneapolis. The BMIU expands to 25 people in the summer and operates on a little less than $2 million a year.
In 2007, Hennepin County’s five-man bridge team inspected all 36 county-owned bridges in Minneapolis. County bridge engineers inspected all 141 county bridges last year, said Hennepin County Bridge Engineer Bernie Jahn. The average age of county-owned bridges in the city is 40. However, just as with city-owned bridges, that number is expected to drop with the replacement of three bridges this year, all more than 100 years old. Jahn said there is no budget for bridge inspections.
Lengthy state criteria says that the county must annually inspect a list of 60 specific bridges, consisting of the very old and the very new.
“But we’re trying, of course, to do them all every year,” Jahn reiterated.
After the I-35W bridge collapse, all county and state bridges deemed fracture critical, or more likely to fail if one component were to falter, must be inspected annually, Jahn said. Currently, county bridge engineers are aiding those from the Minnesota Department of Transportation (Mn/DOT) to inspect a fracture-critical bridge at Washington Avenue, Jahn said.
Minnesota Department of Transportation (Mn/DOT) has 23 certified bridge inspectors working along with five bridge maintenance crews who must inspect every state-owned bridge in the metro every other year. The state must inspect fracture-critical or structurally deficient bridges annually following a 2007 mandate. The state-owned and inspected Interstate 35W bridge was fracture critical. The average age of state-owned highway bridges wasn’t available at press time, however three bridge engineers who spoke with the Journal agreed that they range from at least five to 50 years old. Together, inspectors and crews oversee 1,300 state bridges in the seven-county metro area. An estimated 750–800 bridges are inspected by Mn/DOT in Minneapolis annually.
“[The] Minneapolis area is just kind of a blip on the radar screen,” said Mark Perdula, who has been a Mn/DOT bridge inspection engineer since 1997.
The five metro bridge crews operate on a $550,000 annual budget, said Mn/DOT spokesperson Judy Melander.
However, Melander said she didn’t “feel comfortable speculating” on whether $550,000 was adequate for 1,300 annual metro bridge inspections.
“We’re given so much to get the job done, and we’re getting those inspections made,” Melander said. “The powers that be feel that we’re doing a good job with the resources we have.”