In the four years since the collapse of the Interstate 35W bridge, the state has repaired or replaced 59 deficient bridges, with the last of those jobs to be completed by the end of this fall.

But 75 more bridges remain scheduled for work through 2018.

The projects are part of a $2.5 billion long-range program to deal with troubled bridges before they become safety hazards.

"If we don't keep up with preventive maintenance and timely repairs, typically you're looking at larger investments down the road," said Nancy Daubenberger, head of bridge inspections for the Minnesota Department of Transportation.

Fifty-two of the bridges were fixed or replaced by the end of last year, and work on seven more is expected to be completed this summer and fall.

The program will be funded through $1.2 billion in bonds and $1.3 billion from state and federal tax revenues. Daubenberger said Tuesday that the bridge work is on schedule.

The collapse of the 35W bridge on Aug. 1, 2007, killed 13 and injured 145. In 2008 legislators and former Gov. Tim Pawlenty approved spending to improve deficient bridges.

About one in nine bridges nationwide is rated structurally deficient by the federal government, according to an analysis of federal records by Transportation for America, an advocacy group. Last year, 1,149 Minnesota bridges were deemed structurally deficient.

The designation doesn't mean the bridges are unsafe but that they require significant maintenance and repair to remain open, or need replacement. Deficient bridges may be posted with weight limits.

Major Minnesota bridges already replaced under the program include Hwy. 23 over the Mississippi River in St. Cloud and Hwy. 11 over the Red River in Kittson County.

Work is underway to replace the Hwy. 61 bridge at Hastings and St. Paul's Lafayette Bridge, both of which span the Mississippi.

Pat Doyle • 612-673-4504