CEDAR RAPIDS — Cedar Rapids officials are considering replacing and elevating the Eighth Avenue Bridge — one of the oldest and busiest spans over the Cedar River — so there’s a protected local transportation route during a major flood.
This is a shift from the existing plan to install giant gates at the ends of the bridge to be closed during a flood. The gates would link with the massive protection system shielding properties along the east and west banks.
“It is more efficient for us to raise the bridge with a new structure rather than build a system around the old one,” said Rob Davis, flood control program manager. “Why not just build a wall and set the bridge on top of the wall and have the bridge open during the flood?”
If the new plan is adopted, the bridge piers would be part of the flood protection system while the deck would go over the wall and out of harm’s way from the water, he said. In the 2008 flood, virtually all travel was blocked by the water except for a bottlenecked Interstate 380, Davis said.
To be certain, replacement is more expensive. Despite its age, the steel beam bridge remains in good shape for travel and the bridge is likely to outlive its 80 to 100 years projected life span, Davis said.
But at 78 years old, the bridge is closer to the end of its life than the beginning, the narrow, chipped up sidewalks need a $4 million facelift in the next five years, and the two gates would cost $2 million to $4 million, he said. A rough estimate for the new bridge is $15 to $20 million, Davis said.
The Iowa Flood Mitigation Board, which isn’t required to vote on the matter, reviewed the concept at a meeting earlier this week and gave a verbal thumbs up.
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“Some members on the board come from a hydrological engineering background and asked some pointed questions,” said John Benson, a spokesman for the Department of Homeland Security and Emergency Management, which provides administration for the board. “Once answered, they were comfortable with the proposed change and felt it was a good addition to the project.”
The Cedar Rapids Flood Control System Committee is expected to consider the plans on July 21, and the City Council could be asked to amend the flood master plan to include the changes at its July 26 or Aug. 9 meeting, Davis said.
Davis said if the plan is approved, design work could begin this year, and construction could happen in 2020 and 2021.
Several other bridges span the river, but replacing the Eighth Avenue Bridge makes the most sense, Davis said.
The 12th Avenue Bridge, built in 1974, and 16th Avenue Bridge, built in 1989, are much newer. The Second and Third Avenue bridges were built before 1915 but are still in top shape, they are less critical thoroughfares and they are tied into existing infrastructure, he said. The First Avenue Bridge is a main drag but is tied into existing structures, he said.
The city owns the land needed to replace and elevate the Eighth Avenue Bridge, which opened in 1938 and is a main artery traveled by 18,700 vehicles per day, according to the National Bridge Inventory.
“The Eighth Avenue Bridge is the most logical,” Davis said. “The goal is to keep the city operating. If everything is protected on both sides of the river, and we sill can’t get there, that’s a problem. That was the impetus.”