Poorly rated Hastings Bridge takes another wallop

Engineers have significantly lowered the condition rating for the busy Hastings Bridge -- it carries 32,000 vehicles a day across the Mississippi River -- further downgrading what was already one of the worst-rated bridges in the metro area.

By TONY KENNEDY and PAUL MCENROE, Star Tribune

Last update: February 15, 2008 - 7:30 AM

Engineers have significantly lowered the condition rating for the busy Hastings Bridge, further downgrading what was already one of the worst-rated bridges in the metro area.

The National Bridge Inspection Standards sufficiency rating is 38.1, down from the previous rating of 49.1 on a 100-point scale. The drop is linked to corrosion in the bridge's superstructure, MnDOT said. The section losses were discovered during an emergency inspection in August that followed the collapse of the I-35W bridge in Minneapolis.

A rating of under 50 means that a bridge needs monitoring, might need to be replaced and is eligible for federal replacement funding. The bridge is the busiest two-lane highway bridge in Minnesota, carrying 32,000 vehicles a day across the Mississippi River between Dakota and Washington counties.

Because of its deteriorating condition, the bridge was already scheduled for $2.2 million in repairs beginning in May. Lynn Clarkowski, manager of MnDOT's Metro District South Area, said repairs to the thinning steel will be made at that time.

By 1998, the bridge was already so compromised that MnDOT imposed a 40-ton load limit per vehicle. Last fall, bridge inspectors told MnDOT that the load limit needed to be reevaluated, but in January, MnDOT said no adjustment was needed.

The private engineering firm that MnDOT hired to perform the August inspection also found broken bearings and 76 cracked welds. That inspection report, uncovered last month by the Star Tribune, said the 57-year-old bridge needed immediate attention.

MnDOT spokeswoman Lucy Kender said the additional section loss found by inspectors last fall "occurs in areas of the bridge that do not affect its load carrying capacity."

MnDOT informed area legislators on Wednesday of the change in the rating, rekindling safety worries.

"This alarming information reminds everyone that the Hastings Bridge needs more than just repairs," Sen. Katie Sieben, DFL-Newport, said Thursday. "It needs to be replaced now."

The ratings recalculation means that the Hastings Bridge is now classified under national standards as "structurally deficient," meaning rehabilitation is needed to address the deficiencies.

It is one of only a few metro area bridges to carry that dubious distinction.

The I-35W bridge in Minneapolis had been classified as structurally deficient, as well as the Lafayette Bridge in St. Paul and the Cayuga Bridge in St. Paul.

The Hastings Bridge was already considered "functionally obsolete," meaning that its roadway isn't wide enough and vertical clearance between the deck and overhead truss isn't high enough for modern traffic. In addition, it is one of only two "scour critical" state highway bridges in the metro area, meaning that floodwaters could undermine its timber piling.

And, like the I-35W bridge, the Hastings Bridge is fracture-critical. That means that if one load-carrying part breaks, the whole bridge will fall.

MnDOT said in its latest update that it is currently reviewing the condition of the bridge's gusset plates and hopes to complete its analysis before this spring's repair project.

The steel plates, which connect truss spans in key parts of a bridge, are a primary focus in the National Transportation Safety Board's investigation into the collapse of the I-35W bridge.

In addition, the inspectors found crucial bearings that were tipped, as well as missing bolts and plates. They also said that all 2,800 tack welds in the bridge's steel truss are of "very poor quality and exhibit porosity.''

The bridge is not scheduled to be replaced for at least 10 more years, and the replacement cost is currently estimated to be at least $98 million.

Tony Kennedy • 612-673-4213 Paul McEnroe 612-673-1745