In the coming years, the city of Gillette has a big decision to make about the future of the Gurley Avenue overpass.
In a presentation to the Gillette City Council, Brian Shippy, a structural engineer with Structural Dynamics, said the city should start planning for at least a major overhaul of the bridge, if not a new bridge, in the next few years.
The original surface, or deck, of the bridge, which was built in 1982, lasted 18 years. The first deck overlay, in 2000, lasted 11 years. That was replaced in 2010.
Shippy said each deck overlay has lasted 60-70% of the lifespan of the preceding deck. If this keeps up, the current overlay will last five to six years, he said. It was installed in 2018, meaning it will have to be replaced in 2024.
The city is conducting annual maintenance and inspections on the bridge to extend its life, but even with this, the bridge will need to be replaced some time in the mid-2020s, Shippy said.
Another overlay is out of the question.
“Each successive overlay is getting deeper and deeper into that deck to the point that there’s very little of that original concrete deck remaining,” Shippy said.
If the city tried to do one more overlay, it could break through the bottom of the original deck.
When the time comes to replace the bridge, the city has three options:
- It can fully replace the deck of the bridge. This would involve taking out all of the concrete, reinforcing steel and barriers and building a brand new surface on top of the existing steel girders.
- It could build a new bridge at the current site.
- It could reroute traffic and build a new bridge at a different site.
Shippy recommended the city start planning for one of those options two to three years before the end of the current deck overlay.
All three require a lot of planning, design and money.
The city won’t get much help from the state Department of Transportation. The Bridge Replacement Off System program is a federally funded bridge replacement program to reduce the number of deficient off-system bridges. It applies to bridges owned by cities, towns and counties, located on a non-federal aid roadway and open to the public.
To even get on WYDOT’s radar for the program, the bridge has to reach a certain level of disrepair, city engineer Joe Schoen said.
The Gurley overpass is not at that level yet, so it does not qualify for the program.
“It seems like the state’s working against us,” Mayor Louise Carter-King said. “To get to (that level) we have to give up some of this maintenance that keeps it up.”
“It’s a double-edged sword,” said city administrator Patrick Davidson, adding that the city would be “ill-advised” to rely on the state to help fund this project.
Schoen said even if the bridge reached the level tomorrow, because of the money that has already been allocated, “we’re about seven to 10 years out.”
The city has set aside $1 million each of the last two years for the upcoming bridge replacement.
To completely replace the overpass at the current location could cost anywhere from $15 million to $20 million.
The council has discussed other alternatives to route traffic over Highway 14-16 as well, and costs for those locations have been estimated between $10 million to $16 million, not including costs of buying land to build a new bridge.