All the five lanes on the Plymouth Avenue Bridge are now open after a two-year rehabilitation safety-improvement project.
The bridge was closed in October 2010 after inspectors found corroded concrete and cables inside the bridge's foundational box-shaped girders on each side of the river. The span was opened to both motor vehicle and pedestrian traffic in October 2012, yet lane restrictions were put in place in spring 2013 to accommodate the final construction work.
“When we opened it up the bridge, we found out the cable was in very bad shape,” Jack Yuzna, bridge engineer for the City of Minneapolis, said. “We thought it would be a minor issue but it turned out to be a major issue.”
“Water got inside and eroded the … cables, especially in the middle span of the bridge. That’s why we had to close the bridge,” Yuzna said. “Once we understood how bad it was we had to close the bridge.”
The revitalization and repair work included removal and replacement of corroded concrete and steel cables.
The project was completed in two phases that first included restoration of the main span for both east- and west-bound directions. Phase one required full closure of the bridge. Under Phase, other four spans — two on each side — were repaired as partial traffic was allowed to cross. There are about 10,000 cars and trucks crossing the bridge everyday.
The project cost $7.2 million. The $5.75 million construction fees was paid for by the state, while the City of Minneapolis footed the bill for design engineering, inspection and administrative costs, which is $1.45 million.
The safety issue is another concern during the rehabilitation. The number of motor vehicle traffic lanes was reduced to one in each direction. Additionally, lane delineator was used for spacing each lane. Last but not least, bike lanes were added to improve the bicycle use of the bridge.
“That [bike lane] was an initiative outside of our project,” Yuzna said. “They just happened to coincide and were installed at the end of our project.”
A community celebration was held at the bridge Sept. 7 to mark the complete reopening of the span, which was built in 1982 to cross the Mississippi River.
“They wanted to celebrate the improvement, the fact that it was reopen and the fact that it has bicycle lanes now,” Yuzna said. “It is nice to have it back in a final configuration and to be able to utilize the enhanced bicycle lanes.”
The bridge was close to 30 years old before the restoration, even though it was designed for 50 to 75 years. With repairs, the bridge can last at least 30 to 50 years.
“There was no reason to believe that this won't perform as well as it is always designed to be,” Yuzna said confidently. “We are happy that it turned out well.”
Shengying Zhao is studying journalism at the University of Minnesota.