It’s a nod to the power of water.
Instead of shoving lower Rattlesnake Creek back into an old, unnatural bend through Greenough Park, work is underway this week to let it breathe.
City workers, Trout Unlimited and an excavator from Superior are repairing a 200-foot section of the stream bank above the lower footbridge in Missoula’s oldest city park.
While they’re at it, they’re sporadically closing the asphalt commuter trail to upgrade two culverts that usher runoff from Cherry Gulch and a natural spring into the creek from the west.
High waters in the spring of 2018 pushed the Rattlesnake’s main channel at least 40 feet to the west around a wide arching turn. When the waters went down, a stretch of creek side trail was missing and a hazardous 6-foot vertical bank remained.
“It’s been like that for a year and a half,” said Morgan Valliant, conservation lands manager for the Missoula Parks and Recreation Department.
Crews spent Monday and Tuesday removing 200 cubic yards of earth and building a more natural slope to the creek. Hundreds of willow cuttings were laid on an inner wall of a specially built trench at the toe of the bank. They were covered with biodegradable mats of erosion fabric, a coarser one made of coconut fibers beneath a finer one of jute.
It was all covered with soil, creating what Trout Unlimited’s Rob Roberts called a “burrito of soil.”
“Basically the way to think about it is the erosion fabric and the rocks are kind of like the short-term stability, and the vegetation’s the long-term,” said Roberts, the project director.
As far back as 1913, five years after the fabled flood of ’08 and a couple years after the death of Thomas Greenough, Missoula was riprapping the banks of the stream above the Greenough mansion. Thomas and Tennessee Greenough donated the park to the city in 1902.
It’s not the first time the creek struck back. Roberts pointed just upstream from the current project, where another washout and bank restoration occurred 8 to 10 years ago, he said.
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“The city has basically decided rather than putting the stream back where it was and try to rebuild the trail and fight Mother Nature and fight the river, they were going to actually give it more space and open it up even more,” said Roberts.
Valliant said the asphalt commuter trail on the west side of Rattlesnake Creek traces the path of “the old City Drive” that was built, he believes, in the early 1920s.
“There were a bunch of little culverts under the road, and then it changed into the commuter trail, but those culverts were never replaced,” he said. “They collapsed and failed, and that’s what’s happened over the past few years. Anybody, residents or anybody using the park, will tell you every time it rains we’d have big debris plumes come out onto the trail. In the winter there’d be big ice sheets there.”
In storms, he added, plumes of water spray out from the creek onto the commuter trail, leaving ice slicks if they froze.
With new culverts and the recessed bank, “it’s going to be a lot safer now,” Valliant said.
The $35,000 project will cost Missoula between $15,000 to $20,000 by using workers on the city payroll, he figured. He lauded Missoula’s newest department, the Missoula Storm Water Utility, and its superintendent Bob Hayes for jumping in on project planning.
“It’s a brand new utility that just kind of formed in the last few years,” Valliant said. “It’s been really great to be able to bring that resource into projects like this, to manage storm water so we’re promoting green infrastructure, not taking water to just throw it into the sump.”
The late start in the year was due to the time it took to pull together funding and get permits in place, he said.
While Valliant said the heavy lifting of the Greenough project should be done by week’s end, “unfortunately we’re going to have to finish the work in the spring, to reconnect irrigation systems, rebuild the gravel trails and also to patch the holes we’re putting into the commuter trails for the culverts.
“We won’t be able to get the asphalt in, so we’ll be doing temporary gravel patches.”