Good Question: Are Minn. Bridges Safer Post-Collapse?
MINNEAPOLIS (WCCO) – It didn’t take long after the Interstate 35W bridge collapsed into the Mississippi River for the tragedy and the heroism to transform into calls for action.
“Bridges in America should not fall down so we need to get to the bottom of this,” said Sen. Amy Kloubuchar shortly after the collapse in 2007.
We would learn that the 35W bridge went down because of a design flaw. Messed-up gusset plates couldn’t handle the heavy load.
Yet the attention still focused on an aging infrastructure, and delayed repair work. After the collapse, are Minnesota’s bridges safer?
“We’ve certainly increased and improved up on a number of bridge safety practices,” said Nancy Daubenberger, a bridge engineer for the Minnesota Department of Transportation.
According to Transportation For America, one of every 11 bridges in Minnesota is structurally deficient in some way. That’s a problem in a state with about 14,000 bridges.
According to Daubenberger, since the collapse, there’s a change in the way bridge projects are taken on. Before any bridges are fixed, there’s an independent review of the original design. That’s designed to catch an oversight or error, like the gusset plate design flaw.
“Also we know a lot more about our truss bridges, new federal guidance has come out to determine the load rating capacity,” she said.
Also, older non-redundant bridges get more inspections now. If one thing fails in a “fracture critical” bridge, the entire bridge could fail, as happened with the 35W bridge. Before 2007, those bridges were inspected every year, and had an in-depth inspection every four years. Now those in-depth inspections happen every two years.
And there’s been a considerable amount of construction since 2008.
“Those were funded as part of special funding that came out of 2008 legislature focused on fracture critical bridges and structurally deficient bridges,” said Daubenberger.
The so-called Chapter 152 program passed by the state legislature in 2008 committed $2.5 billion over 10 years to bridges.
“That’s definitely an increase over what we were spending,” she said.
The northbound Lafayette Bridge in St. Paul will be done next year, the southbound by 2014. The Highway 23 DeSoto bridge in St. Cloud is already done. Construction on the Highway 61 bridge in Hastings is underway.
By the end of next year, MnDOT says 59 bridges will have been rehabbed or replaced since the 35W collapse. By 2018, 120 bridges will be done.
“The bridge collapse and the tragic events triggered the special funding,” said Daubenberger.
But 4-years isn’t enough time to magically fix thousands of old bridges. In Minnesota, 2,900 bridges are more than 50 years old, according to Transportation For America. The state average age for bridges is 35.2-years-old — better than the national average of 42-years-old.