The Highway 61 bridge in Hastings is even worse than the Minnesota Department of Transportation thought. On Thursday, MnDOT downgraded the "sufficiency rating" of the bridge by more than 20 percent.
Rust on the bridge is the main factor for the drop.
The bridge had been rated 49.1 and is now at 39.1. The Interstate 35W bridge that fell into the Mississippi River Aug. 1 had a sufficiency rating of 50 at the time of the collapse.
MnDOT uses structural adequacy and safety (55 percent), serviceability and functional obsolescence (30 percent) and essentiality for public use (15 percent) to determine sufficiency ratings, according to a press release from District 57 Sen. Katie Sieben, DFL-Cottage Grove.
According to Sieben's press release a MnDOT bridge official sent her an e-mail saying this summer's bridge repair work will "slightly improve" the bridge's sufficiency rating.
"We are spending over $2 million on a re-hab project that may only 'slightly improve' the bridge's rating," Sieben said in the press release. "The Hastings Bridge is the most heavily traveled two-lane bridge in Minnesota. It's time to end the Band-Aid approach and move forward with bridge replacement."
The Hastings Bridge is fracture critical, meaning that if one element of the bridge were to fail, the bridge could collapse. It's also functionally obsolete, meaning that it no longer meets MnDOT roadway standards because it funnels four lanes of traffic down to two and doesn't have a shoulder, among other reasons. Additionally, the bridge is scour critical, which means river currents have damaged the bridge's supports.
Currently the Hastings Bridge is scheduled for replacement in the "early years" of a MnDOT planning period that runs from 2015-2023.