At Knowlton Creek, which flows through the Spirit Mountain Recreation Area, the Minnesota Department of Natural Resources is overseeing one of the most ambitious single stream restoration projects in state history.
"We're restoring about 6,500 feet (about 1.2 miles) of coldwater stream habitat," said John Lindgren, a senior fisheries specialist and St. Louis River area of concern coordinator for the DNR.
All told, about $1.5 million will be invested in the project, with funding coming from the Environmental Protection Agency, the Minnesota Outdoor Heritage Fund and the National Fish and Wildlife Foundation, among others.
"There have been a lot of erosion and sediment problems, and we're trying to address those," Lindgren said.
"So we want to button up the sediments, and the way that you do that is to recreate a natural stream channel design that also provides good habitat for fish and other aquatic organisms," he said.
The creek is one of 16 designated trout streams in the city of Duluth, but it had been so badly degraded that brook trout once native to the waterway had been driven out of it. Lindgren said the DNR has been working for the past few years to reintroduce the fish, and when the project is completed, Knowlton should provide better habitat for brookies to successfully live and reproduce.
On Wednesday afternoon, excavators were hard at work below a waterfall on Knowlton Creek, deftly piecing together boulders and smaller rocks to form a series of step-like levels in what will become the waterway's new channel when the project is complete.
Mike Adams of Stantec Consulting, a stream restoration firm, said finding the right materials for the job has been one of the biggest challenges. Some of the rocks were readily available on site, but they had to be supplemented with quite a number of boulders hauled into the steep valley.
Lindgren said the project will re-establish a floodplain, "so high water can get up on the floodplain and dissipate its energy without ripping apart the banks."
"In many spots in Knowlton Creek, the way it was, the stream channel had become incised or dug-in," he said. "It was entrenched, so the water could not get up and out of its banks, and all the energy in a flood just kept ripping more and more sediment off the banks."
It didn't help that runoff from neighboring Spirit Mountain's snowmaking operations caused the stream to swell each spring. Lindgren estimates the snow added about 20 percent to the creek's natural flow in a typical year.
"That added runoff and flow ended up providing energy that ripped apart the stream," Lindgren said.
But a new pipeline that allowed the ski hill to begin drawing water for its snowmakers directly from the St. Louis River also now doubles as a conduit to carry the melt-off back down each year, reducing the impact on Knowlton Creek.
Lindgren called the design of the system "cutting-edge" and said Spirit Mountain deserves credit for doing its part to nurse the stream back to health.
He said the project now underway "involves a fair amount of cutting and filling and changing where the actual stream channel is located, so that you can establish a floodplain and get the water away from eroding banks."
"In some places we're cutting the banks down. In other places we're filling them in. But the goal is to create enough of a floodplain where you can dissipate that energy," Lindgren said.
The stream's erosive force is evidenced by many of the deeply gnawed dirt banks along its recent course.
Lindgren said Knowlton Creek carried and spilled so much sediment into the St. Louis River that it filled in once-open waters around Tallus Island. A recent project there removed 55,000 cubic yards of sediment from that area of the river.
Earthwork associated with the current project is again muddying Knowlton Creek, but Lindgren contends the long-term benefits will far outweigh the temporary impacts on the stream.
"We have to make things worse before they get better," he said.
So far, about 3,500 feet of Knowlton Creek and an unnamed tributary have been restored, and Lindgren expects the project to be fully completed by October.
Workers are laying a biodegradable mesh fabric is over disturbed soils in the recontoured floodplains of the watershed. They are being planted with fast-growing oats to provide an initial vegetative cover, but Lindgren said native plants, including hundreds of trees, soon will be added to the mix to stabilize soils for the long term.
The U.S. Army Corps of Engineers provided design funding for the project, which is part of the Great Lakes Restoration Initiative.