A portion of Zimmerman Trail remains closed and will stay closed for the foreseeable future after a rockside Tuesday, Billings Public Works Director Dave Mumford said Wednesday.
Public Works officials estimated Tuesday that they’d have Zimmerman Trail reopened by April 1, but an engineer’s assessment has pushed that date back.
“We don’t know when it will be safe to reopen,” Mumford said of the stretch of Zimmerman Trail from Rimrock Road to Highway 3.
Only local traffic is being allowed into subdivisions near the lower portion of the closed roadway.
An engineer’s assessment indicates that the rock on the cliff face behind the rocks that slid onto Zimmerman Trail is also unstable. Mumford said the rocks that are in danger of coming down amount to “as much or more” rock as cascaded onto the roadway early Tuesday afternoon.
The Montana Department of Transportation is working to find federal highway funds to hire a contractor to clear the loose rock still clinging to the slide slopes, Mumford said. The work was scheduled in the next year or two, he said, so MDT is trying to expedite the delivery of the funds to pay for the removal this spring.
The situation is so unstable that it’s too dangerous for city road crews to enter and begin repairing the damaged roadway and replacing up to 250 feet of guardrail, Mumford said.
It also doesn’t make sense to replace the damaged and missing guardrail if more rocks will eventually slide down, he added.
“If they were pounding on supports for those guardrails, it’s liable that more rocks would be let loose,” Mumford said. “With that in mind, we’re hard-pressed to feel safe allowing vehicles or even workers into the area.”
Even after a contractor removes the rock that’s deemed most likely to slide, even more rock could come down because of this winter’s severe freeze-thaw cycle, Mumford said.
Asked to rate the problem on a scale of 1 to 10, Mumford assigned the rockslide “an 8 or 9.”
“It’s a major road we have closed,” one that sees between 6,000 and 7,000 vehicle trips per day. “The city is working on it, and MDT is working with us to try to figure out how quickly we can resolve the problem and get it open. But we don’t want to do that if there is any concern anything could happen.”