Parts of the sidewalk’s edge on the university side of the Madison Street Bridge have crumbled away, leaving a gap in one spot through which a wayward leg could fit easily and uncomfortably.
On the other side, Missoula's traffic services coordinator Wayne Gravatt plugged a hole through the walkway with an inverted orange cone early Monday – and figured it was time to call in the posse.
Major bridges like this one are built and repaired by the Montana Department of Transportation. Dave Crumley, bridge maintenance engineer for MDT, drove over from Helena on Tuesday to inspect the damage from a bucket lift.
"What we found is the sidewalk portions are structurally deficient," said Steve Felix, MDT's Missoula maintenance chief. "We've got support piers for the sidewalks that are not in very good shape."
"We won't be reopening the sidewalks any time soon," he added.
Felix stressed that the bridge itself remains safe to drive on. It's scheduled for an extensive rehabilitation in 2020, sidewalks and all.
"We were hoping to get it to that project, but we aren't going to be able to," Felix said.
“Spalling” – deterioration of the concrete caused by freeze-and-thaw cycles – has reached a point on both sides of a 60-foot section of bridge deck that walkways lining them are safety hazards. Some chipping underneath has occurred, though no one has reported bridge debris falling on them.
By Monday afternoon, would-be pedestrians at both ends and either side of the bridge were greeted by upright cones and signs that read “Sidewalk Closed. Use Other Route.” Luckily there’s a good alternative – a $1.25 million “under bridge” for walkers and bikers that opened in 2006.
A section of the Ron MacDonald Riverfront Trail directly under the problem area has been barricaded off with an off-pavement detour assigned. Felix said the Missoula Parks and Recreation Department will install a chain-link fence in place of the barricades on Wednesday.
A complete repair plan had not been settled on by Tuesday evening.
The Madison Street Bridge, farthest upstream of five vehicular bridges that span the Clark Fork River in Missoula, was built in 1958 and last rehabilitated in 1981.
Why only one section of its sidewalks is deteriorating – the one above the riverside trail – is a matter of speculation.
"We're not totally sure," Felix said.
He and Crumley speculated it might have something to do with the railroad.
What's now the Riverfront Trail was once the bed of the Chicago, Milwaukee, St. Paul and Pacific railroad – aka the Milwaukee Road – which ran trains powered by overhead electric lines from 1917 to 1974. The last Milwaukee train came through town in 1980, the year before the most recent bridge rehab.
A Missoula bridges planning study completed in 2014 recommended that the Madison Street and Higgins Avenue bridges be rehabilitated with new decks that include wider bike lanes and sidewalks. Downstream, the Russell Street Bridge is due to be totally replaced in 2017.
Shane Stack, MDT’s Missoula project engineer, said that while work on the Madison Street Bridge is scheduled for 2020, "that can always change."
The Higgins Avenue Bridge project has yet to be scheduled, he said.