Plymouth Avenue bridge update

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The City of Minneapolis Sept. 2 made some final financial arrangements for repairing the Plymouth Avenue Bridge next year, and the project is set to cost less than was initially expected.

The City Council added the repair project to its Five-Year Capital Program, increased funding for the Bridges Capital Program and its Minnesota Department of Transportation (MnDOT) revenue source to $6,145,528, authorized acceptance and expenditure of $2,145,528 from MnDOT Municipal State Aid disaster funds, authorized acceptance and expenditure of $4 million in MnDOT State Bridge Bonds, and approved a $55,000 contract amendment for the engineering firm that’s planning the repairs, so it can be retained as construction manager for the repair project. This brings the total for that firm to $305,000.

All this dots the i’s and crosses the t’s to allow the city’s public works staff to get bids and execute contracts for the repairs.

City engineers closed the bridge last Oct. 22 after finding corrosion in its support system during a routine annual inspection. It was built in the 1980s and was the first of its kind—called post-tension segmental box girder—in Minnesota. City officials brought in Corven Engineering, a Florida consulting firm that specializes in this bridge design, to inspect the bridge and recommend repairs.

City engineers closed the bridge Oct. 22 after finding corrosion in its support system during a routine annual inspection. It was built in the 1980s and was the first of its kind—called post-tension segmental box girder—in Minnesota. City officials brought in Corven Engineering, a Florida consulting firm that specializes in this bridge design, to inspect the bridge and recommend repairs.

Corven’s initial report, issued in late December, recommended four major repairs:

  • Reconfigure the bridge’s drainage system to direct water away from the bridge’s box girders
  • Replace five of the bridge’s corroded support tendons
  • Add more tendons to improve the bridge’s flexing capability
  • Seal the bridge’s wearing surface with a penetrant sealer, or replace the wearing surface.

 

Later inspections and computer modeling determined that the damage is not as bad as was originally thought, according to a report from the city’s Public Works Department. “Initial repair estimates placed the cost at between $7 million to $10 million. The computer modeling and structural analysis found that the bridge was very robust when built. The later field investigation also found that damage to the four outside spans was not as broad/extensive as initially thought. These findings have resulted in a reduction to the scope of repairs needed to return the bridge to full service and reduced the project cost estimate to $6 million.”

The report also details how the planning and contracting work is expected to proceed. “Completion of the bid documents is currently underway and will need to be submitted to MnDOT for review and approval,” the report states. “We anticipate to have authorization to advertise for bids this fall but may elect to wait if it appears the bid environment will be optimal in December. It is Public Works intention to award the contract and issue notice to proceed such that the contractor will be able to start work as early as spring weather permits. Construction is anticipated to be completed in three to four months after which the bridge will be opened to all traffic.”

The bridge is currently open to pedestrians and bicyclists; bicyclists are asked to walk their bikes while on the bridge.

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