The bridge, which spans the Mad River, is a popular connection used by joggers, bicyclists, dog-walkers and other downtown visitors.
Last year, Montgomery County inspectors recommended closing the roughly 434-foot bridge because of a weakened bottom chord of the truss, according to the 2018 inspection report.
Montgomery County Engineer Paul Gruner said a square steel tube was rusting from the inside out, causing holes in the metal.
Tests revealed that there was enough steel lost to corrosion to significantly reduce the load-carrying capacity, Gruner said.
The rusting square steel tube is similar to one in a ride that failed at the Ohio State Fair in 2017, he said. One person was killed and seven others were seriously injured when a gondola on the ride snapped off.
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Inspectors noted that there was noticeable movement in the bridge when one or more runners were using it.
The Montgomery County Transportation Improvement District has entered into an agreement with MetroParks for planning work related to the pedestrian bridge.
MetroParks will pay the improvement district $45,000 for its assistance evaluating the bridge and coming up with engineering options or alternative plans, said Steve Stanley, executive director of the transportation district.
“We’ve been asked to help look at what the steps might be” to demolish or replace the bridge, he said.
The district’s fee will be about $25,000, and the rest is expected to help cover out-of-pocket costs for third-party services like engineering work, Stanley said.
The improvement district helps finance and expedite transportation and other improvement projects. The district will provide technical assistance to determine the costs of demolition or replacement and potential ways to fund such a a project, Stanley said.
The agreement says a “consortium” of local jurisdictions and other organizations are likely to be involved in planning and financing the project.
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Some steel tubing with significant rusting was found on the west side of the bridge. The deck drainage falls to the western side of the bridge, which is within overspray reach of the RiverScape water fountains, the inspection report states.
“We do think the fountains contributed due to frequent wetting of the structure. The deck drainage may also have contributed, but probably not as much,” Gruner said.
The pedestrian bridge is made of painted weathered steel. The paint is fading and oxidized, especially on the west side due to spray from the fountains, the inspection states.
MetroParks closed the bridge to light vehicle traffic in 2017 following an annual inspection that identified corrosion.
The bridge was built by Mainline Road & Bridge Construction Inc.
The bridge has two large concrete piers, concrete approaches, landscaping and electrical components.
If the steel structure needs replaced, other parts of the bridge should be reusable, county officials said.