The final phase of restoration in #GlenwoodCanyon turns to debris-choked #ColoradoRiver: CDOT is orchestrating the removal of hundreds of thousands of tons of debris flushed down the walls of Glenwood Canyon in July deluge — The #Colorado Sun #COriver #aridification

Glenwood Canyon and the Colorado River. Photo credit: CDOT via Roads & Bridges

From The Colorado Sun (Jason Blevins):

In a week or so, CDOT will announce it has completed repairs of Interstate 70 in Glenwood Canyon. Crews have finished rebuilding the roadway, thanks to a unified push by a host of federal and state agencies.

The impacts of the 2020 Grizzly Creek Fire that burned more than 32,000 acres in the canyon remain acute, with the scar still likely to shed rocks, timber and mud during next spring’s melt. More than 4 inches of rain on July 29 — following several days of rainstorms — shed rocks, mud and trees from atop the canyon. Six massive debris piles span a 3-mile stretch of highway and river in Glenwood Canyon. Early attempts to measure the muddy mess set it at more than 100,000 cubic yards. If it was just dry sand, that would be about 150,000 tons. CDOT estimates it has already removed about 44,000 tons of debris off the highway and recreation path.

The worst-ever debris-flow damage to the vital interstate corridor has been repaired in a little more than four months. It would probably be easier to list the federal and state agencies that were not involved in the restoration work, but CDOT led an effort with input from the Army Corps of Engineers, the U.S. Forest Service, the Federal Highway Administration, the Colorado Department of Natural Resources and just about every nearby community and Colorado River water guardians…

With teams working on the debris-choked Hanging Lake Trail as well as seeding the burn zone to hasten growth that can prevent devastating runoff, the final stage in the restoration of the Colorado River in Glenwood Canyon begins now, with plans to clear plumes of rocks and mud blocking the Colorado River in the canyon. Crews soon will position heavy machinery in the river bed as part of a complicated plan to clear six river-jamming piles.

CDOT officials flew over the canyon this summer and mapped the river and the new debris fields using laser technology. Then a hydrology consultant created models for various runoff scenarios, looking at how the jumbles of rocks in the river might disrupt flows when the dam at Hanging Lake spills and the narrow canyon sees the river swell to 5,000, 10,000 and even 15,000 cubic feet per second next spring.

“Based on those models, we are showing the potential for catastrophic damage to eastbound 70 if the river is left in its current configuration,” Knapp said. “That is the main driver for the removal of that debris.”

[…]

CDOT will start digging soon, chipping away at the piles until trucks have hauled away at least 60% and up to 90% of the debris choking the river and bike path in the canyon. That’s good news for downstream water users, anglers and rafters. But CDOT isn’t spending federal dollars to keep trout biting and rafts floating. It’s all about protecting the highway to the north and the railroad to the south of the river…

Six debris piles threatening I-70

CDOT plans to remove six debris piles by the end of April next year, before the spring runoff swells the Colorado River. Its emergency road repair contractor, Lawrence Construction Co., is on board to work the two piles that flowed from the north. The Lawrence group also plans to clear the recreation path along the river, but the priority is to clear the river before the end of April 2022.

Looking up at the source of the debris flow in Glenwood Canyon August 2021. Photo credit: CDOT

The debris pile that poured down Blue Gulch on the north side of the highway and damaged both the westbound and eastbound lanes did the most damage to the highway and buried the largest portion of the river. That pile erased a Class IV rapid known as Barrel Springs. One mile upstream, debris from from the north side’s Wagon Gulch went beneath the westbound lanes but buried the low-lying eastbound pavement. That’s the debris pile that could most easily force the river onto the highway, Knapp said…

Those two piles — below the Blue and Wagon gulches — are more logistically straight forward, with Lawrence Construction crews able to access them both from a single closed lane on the eastbound highway. And they are in the stretch of river between the Shoshone Dam at the Hanging Lake rest area and the Shoshone Generating Station, which is regularly dewatered in the winter months as Xcel Energy diverts the Colorado River into a tunnel that feeds the hydroelectric power plant.

The piles that came from the south, over and under the railroad, are more challenging for removal crews. CDOT will soon begin seeking contractors who can work with the Union Pacific railroad to access two of those piles above the Shoshone power plant, which are below Devil’s Hole Canyon and an unnamed gulch that CDOT has dubbed Unnamed…

Later this winter, the transportation department will hire contractors to help remove the two piles downstream of the power plant, which are below Deadman Gulch and above the Maneater rapid. (Those last two will be trickier, because the river is flowing there and crews will likely be unable to access the highway to remove debris.)

CDOT has a unique plan for the Devil’s Hole and Unnamed piles. The rocks and mud that flowed down Devil’s Hole Canyon funneled beneath the railroad tracks and slammed into the eastbound highway retaining wall, completely blocking the river. CDOT hopes a contractor can work with the railroad to deliver equipment to the debris piles but then build a temporary debris bridge across the river so earthmovers can load trucks on the highway. The plan for a debris bridge is the same for the Unnamed pile. That way no debris would be removed via the railroad.

But downstream, in the heavily rafted Shoshone stretch of the Colorado River, the two piles at Deadman and Maneater will require more coordination with Union Pacific. The railroad has given CDOT a four-hour midday window between its passing trains to load and remove train cars with debris. CDOT’s yet-to-be-issued request for contractors is hoping to find a company that can speedily fill train cars while working on the edge of the moving Colorado River…

The Forest Service and CDOT, recognizing the critical role rafting plays in the local economy, opened early access to the river for several owners of rafting companies.

It was quite a scene, said Ken Murphy, the owner of the Glenwood Adventure Company. Nine or so competitors, working together in the middle of rapids with ropes, chainsaws and winches to clear dense walls of timber clogging the rapids above Glenwood Springs.

“We just had to get it open,” Murphy said, “and get our businesses back up and running. The river is an important economic driver for our community. There is huge support to get that cleaned up and ready.”

After two days of sawing and yanking, they cleared a path for rafts. Then the owners brought in their guides, who had to learn how to navigate a completely different river. The jagged piles of rock at Deadman and Maneater have changed how rafts and kayaks descend the rapids.

That’s not necessarily new. After exceptionally snowy seasons in Colorado, Shoshone stretch can see flows reach 15,000 or even 18,000 cubic-feet-per-second in the spring. (For comparison, the stretch typically runs around 1,200 cfs.)

Those rowdy runoff flows shift rocks and reorient rapids. Murphy said commercial and private whitewater paddlers are closely watching how the debris removal might change rapids…

CDOT’s Knapp is a kayaker. He lived in Glenwood Springs. He’s confident that removing debris from the side of the river channel will not alter the rapids. When the project is wrapped, he expects the river to look and paddle a lot like it did before the summer rockfall. He knows he’s not spending millions in taxpayer dollars so whitewater paddlers can still enjoy the river. But recreation is an important consideration and one of the resources the Forest Service wants to protect in Glenwood Canyon.

Leave a Reply