Renovating three of the five spans of the historic Old Cedar Avenue bridge and replacing the other two could cost $7 million or more, the city of Bloomington has learned.

That's twice the estimated cost of building a new bridge to handle pedestrian and bike traffic as well as the occasional emergency vehicle. And it's way beyond the $3.3 million the city has secured so far in state and federal funds to replace the old bridge.

While preservationists would like to save as much of the unusual 1920 bridge as possible, cost will be a major issue for the city.

Rep. Ann Lenczewski, a Bloomington DFLer who this year played a key role in getting $2 million in state bonding money for replacement of the bridge, said the preliminary cost estimates to save all or part of the bridge appear too costly to be practical.

"I anticipate that the decisionmakers ... will return to the original plan and the goal of my bill, which is to remove the bridge and replace it with a new span," she wrote in an e-mail.

The camel-back steel truss bridge, which has been closed since 2002, is eligible for listing on the National Register of Historic Places. Bridge historians say that the loss of similar structures in the state has made the Old Cedar Avenue bridge a Minnesota rarity, unusual for its 865-foot length and five arched spans.

Engineers and historians are evaluating the structure's condition and historical importance, as required by the federal appropriation. This week, Bloomington was the host of an information session to update the public on the evaluations of the bridge.

Once part of a heavily used crossing over the Minnesota River, the bridge was closed to vehicle traffic in 1993, and now crosses only Long Meadow Lake in the Minnesota Valley National Wildlife Refuge. Before it was totally closed because of safety concerns, the bridge was used mostly by bird watchers and hikers enjoying the refuge and by recreational and commuting bicyclists.

While final engineering and historical analyses may not be ready until after the new year -- along with firm estimates of the cost of renovating all or part of the bridge -- a clearer picture of the bridge's condition is emerging.

In general, much of the interlocking steel that forms the arching spans above the decking is in fair condition, though it is covered with rust and some beams would need to be straightened, according to the engineering firm of Kimley-Horn and Associates Inc., whose findings were detailed in displays at the meeting this week.

But the concrete piers supporting the bridge are visibly crumbling. Bearings on the entire bridge are classified as in "critical" condition, one step up from imminent failure. Some of the decking is missing. And the floor beams are at risk of failing at any time, engineers said.

Robert Frame, senior historian with Mead & Hunt Architecture of Minneapolis, said rehabilitation is often a way to keep old bridges. "It would not be a museum restoration," he said, "but a lot of it could be reused."

While the costs associated with rehabilitating all or part of the bridge have not been firmly established, Bloomington Deputy Director of Public Works Jim Gates said estimates for rehabbing the bridge's middle three spans and replacing the two at either end are hovering between $7 million to $8 million.

"Rehabbing the total bridge is significantly more expensive," he said.

Hybrid option

That so-called hybrid option between rehabilitation and replacement would preserve the soundest parts of the old bridge while sacrificing the two end spans, one of which is in especially rough condition. But it would still be twice as expensive as replacing the entire bridge with a new structure.

Bloomington City Council Member Steve Elkins stopped by the meeting to talk with the experts.

"It would be nice if some portion of the original structure could be retained for historic preservation," he said in an e-mail afterward. "However, if it's not financially feasible to do so, we're not going to let that stand in the way of building a new structure that meets the practical needs of the users of the bridge."

History buffs are still hoping that all or part of the bridge can be preserved. DFL Sen. Jim Carlson of Eagan said that while he doesn't favor spending an exorbitant amount of money to save the bridge, he thinks more economical alternatives can be found to save parts of it.

Vonda Kelly, president of the Bloomington Historical Society, also would love to see the bridge saved. But she's a realist, too.

"In the final analysis, different things will dictate what happens -- the cost, for one thing." She said the estimates that are emerging "don't surprise me much. But I think we need to take a closer look at them."

Mary Jane Smetanka • 612-673-7380