Painting Hubble Creek pedestrian bridge caused faster deterioration

The pedestrian bridge over Hubble Creek in Jackson City Park is a landmark, the go-to backdrop for senior photos and wedding parties. Children play on it. Joggers include it on their daily exercise routes. City crews decorate it for Christmas.

That city crew in late fall 2016 discovered structural areas of concern partly caused by painting the bridge years ago, said city engineer Erica Bogenpohl at the Feb. 6 board of aldermen meeting in Jackson.

Koehler Engineering in Cape Girardeau performed a structural analysis of the bridge in December and determined there was not a significant danger of catastrophic failure, but repairs were needed.

"Generally, we are looking at a bridge of similar size, structure, material. We are leaning away from the corten steel in lieu of a painted or coated steel," Bogenpohl said.

Corten is an industry term for "weathering steel," which is designed to develop a patina of rust. This coating helps protect the steel from corrosion, according to Frequently Asked Questions on corten.com.

Bogenpohl said in the past, the bridge's steel frame was inadvertently painted, which is counter to its maintenance instructions.

"When you paint a weathered steel bridge, it advances the deterioration," she said. "Paint traps moisture against the steel. It's not good for it. But that was years ago somebody did that."

That painting has led to excessive rust on the steel frame, which coupled with the wooden deck's deterioration, is a significant concern.

At the Feb. 6 board of aldermen meeting, the board approved an allotment of $10,800 to Koehler Engineering & Land Surveying of Cape Girardeau for the bridge project. This allotment covers design of the bridge replacement and included assistance applying for a grant to fund the project, Bogenpohl said.

Several options were considered during the grant application's early stages, Bogenpohl said, including relocating the existing bridge to another point on Hubble Creek, repairing the existing bridge or building a new structure.

Relocation was discussed but ultimately nixed, Bogenpohl said.

To replace the bridge, "we are hoping to do everything, including removal of the old bridge, for under $100,000," Bogenpohl said. "To relocate the bridge would have added $35,000 to the project. We just didn't think that was fiscally responsible."

Additionally, the bridge's foundations "are in fine shape," Bogenpohl said, and relocation would have required a crane and additional equipment.

Walking trails also would have needed to be rerouted to accommodate the bridge.

Repairing the bridge would have been similarly problematic, Bogenpohl said. Sandblasting would have been necessary, but that process would produce contaminants.

"It would be a major undertaking to capture [that]," she said. "We couldn't have the debris from the cleaning operation enter Hubble Creek."

Another option would be to physically remove the span, set it aside and clean it, but that would require a crane, Bogenpohl said.

Even with the cleaning and repairs, Bogenpohl said, at the end of an expensive process, the bridge would still need to be replaced eventually.

"It is a 35, 36-year-old bridge. I can't tell you what the design life is, but we are well into it. All signs point to replacement being the most feasible option," Bogenpohl said.

The new bridge's design will be substantially similar to the present bridge.

"We want to get away from a rusted-look steel. We don't want to have a modern-look bridge necessarily, but something that would be less maintenance and have a nice look to it," she said.

Bogenpohl said a deck of concrete instead of wood would be lower maintenance in the long run, although it adds about $5,000 to the bridge's upfront cost. The concrete could be stamped with a variety of patterns.

"The crosswalks in uptown Jackson have a fractured earth look," she said, but other designs are available, including brick and woodgrain.

"We definitely want to preserve the nice aesthetic look the bridge has now," she said.

For projects such as this, the Missouri Department of Natural Resources offers a 50 percent match grant through the Land Water Conservation project, Bogenpohl said, and Koehler has provided assistance with the application.

"We've applied for the grant in the past," Bogenpohl said, noting the city was awarded a grant in 2014 for the city of Jackson soccer park.

The DNR will announce whether the city has been given the grant in July.

Koehler Engineering will handle the construction, Bogenpohl said.

Of the bridge, Bogenpohl said, "We know it's a popular spot for photographers, amateur and professional. A lot of people go there for their proms and senior pictures, weddings. We know that's a popular spot and traditional feel in that corner of the park. We want to preserve that."

mniederkorn@semissourian.com

(573) 388-3630

Pertinent address: Jackson City Park, Jackson, MO