Monday's tumbling of two rocks above Zimmerman Trail has led city officials in Billings to look for other potential sites for rock slides.
They've found one in Swords Park, but the fix might cost an additional $500,000.
The Billings City Council voted unanimously Monday evening to allow a Colorado company hired to remove some rocks and stabilize others above Zimmerman Trail to do similar work on one particular rock formation in Swords Park in danger of falling onto Sixth Avenue North.
Last week, the Montana Department of Transportation hired GeoStabilization International of Grand Junction, Colo., for a $718,219.68 rock removal and stabilization project at six locations along Zimmerman Trail. Two rock falls — one at 2:30 a.m. Monday, the other at about 1:30 p.m. Monday — led to the closure of Yellowstone County’s Zimmerman Park and to what Billings police called strict enforcement against people trespassing on the closed portion of Zimmerman Trail.
Public Works Director Dave Mumford said that while the company is in town, it will also be retained to remove a rock he estimates weighs several hundred tons from Swords Park.
The rock formation in question, noted council member Angela Cimino, "looks like a monument."
Following the March rock slide above Zimmerman Trail, the public works department asked its consultant, Terracon of Billings, to look at other areas of concern in addition to Zimmerman Trail, including Swords Park.
City Administrator Tina Volek called the Swords Park situation "an emergency" and said city staff would return to the city council with a plan for funding the additional work.
"Were it something less serious, I wouldn't be recommending this to you," Volek told the city council.
Care must be taken, Mumford said, not to allow a falling rock to damage utilities that are buried under Sixth Avenue North.
City engineer Debi Meling said she was at the Zimmerman Trail site on Monday morning after the first rock fall and had to tell about eight onlookers to move along to avoid being injured by another series of cascading rocks.
“Because the second rock was obviously coming down, we got serious about people not getting out there,” she said. “What happened (Monday) is exactly what we have been afraid of. With this winter’s freeze/thaw and all the wet weather, this is one of those years you can expect to see this.”
“We would be wrong,” she added, “not to take advantage of (GeoStabilization International) being here.”
Meling said a GeoStabilization International crew mobilized right after learning it had been awarded the Zimmerman Trail contract and was expected to get to work on site by 10 a.m. on Tuesday. Company personnel evaluated the Swords Park site Monday afternoon and gave Mumford the $500,000 estimate shortly after that.
Actually, the estimate was about $700,000, Mumford told the city council, but public works employees can do about $200,000 worth of work themselves.
Late last week, Mumford estimated the Swords Park work would cost about $200,000. But GeoStabilization International reported that bringing the rocks down would require significant piles of dirt, which drove the estimate up.
“With this crew, it is very specialized work,” Meling said. “We knew they were coming, and so we decided to look at other areas where we had concern. We tend to get a lot of rocks at the intersection (of Sixth Avenue North and Main Street).”
GeoStabilzation International’s contract along Zimmerman Trail is for 25 days, Meling said. After that work is done, city road crews will repair the guardrail and repair damaged pavement before reopening the street, closed since the late March rock slide.
Volek said that city officials will need to revisit possible rock dangers every two or three years in order to help avert a catastrophe.
"As a city we need to figure out a way to address this so it isn't always crisis management and doesn't cost us a half-million dollars out of the budget," said council member Denis Pitman.
On Monday, Duane Winslow, Yellowstone County’s director of Emergency and General Services, announced the closing of Zimmerman Park. No one is allowed in the park, located immediately west of Zimmerman Trail and bordering the edge of the Rimrocks, until further notice, he said.
Yellowstone County’s road and bridge crews were putting up barricades at the entrance of the park and sheriff’s deputies will be monitoring the area, he said.
Cal Cumin, county parks director, said the Zimmerman Park closure should be only for a few days while dangerous rocks are being removed.