The "Iron Bridge" on the outskirts of Northfield has been rated the "most deficient" bridge in the state. A deal has been reached to build a replacement span.

By David Peterson

May 22, 2008 at 4:41AM

The worst bridge in Minnesota is about to be replaced.

The "Iron Bridge" over the Cannon River on the outskirts of Northfield has an extraordinarily rare sufficiency rating of 0.00. It has long hovered on the edge of closure.

One sign of how bad it is: Just preserving it for long-term use by bikers and pedestrians will cost $200,000.

"We are monitoring it all the time," Tom Anton, Dakota County design engineer, said Wednesday about the bridge, which is No. 1 on the state's list of deficient bridges. "If it gets any worse at all, we'd strongly consider closing it."

For the moment, however, it remains open to the trickle of vehicles that make their way across a gravel road and use it as a shortcut between two busy state highways.

About 400 cars cross it per day, according to Dakota County officials. They are so serious about ensuring that nothing too heavy tries to sneak across and ends up in the river that a metal piece has been welded onto the bridge to keep anything too tall from crossing.

One challenge in replacing the bridge is that it's located near Carleton College's Cowling Arboretum. It has taken a long time for the college, the state, Dakota County and Waterford Township to work out a deal to cross that land with a new bridge while retaining the old one as a link in a future state trail. That deal was announced early this week.

Movement on the old bridge was not affected by the I-35W bridge collapse in August, Anton said. "We were already working on this at that point."

Indeed, the issue has been under active review since 2004, according to a statement from Carleton.

The new bridge, at about 300 feet, will be much longer than the old one and will be several hundred feet upstream. It is expected to cost about $1.5 million, and construction is to begin as soon as this fall.

The bridge is a shortcut between the two major arteries -- Hwys. 47 and 19 -- leading eastward out of the northern part of town.

"It's definitely out of the way," said Eric Sieger, spokesman for the college. "I live in Northfield, and I've never even been over it."

Waterford Township, in which the bridge is located, has agreed to add a boat launch as part of the project to enable canoes and kayaks to reach the water, according to the statement. If that means ownership of that piece of land needs to pass to the state, the college said, that's fine.

"People are using it for that purpose already," Sieger said, "so adding a launch will make it safer for everyone."

David Peterson • 952-882-9023