As Inga Gok and her energetic Belgian shepherd explore the newly-terraced mudflats along Cherry Creek, east of South Quebec Street, they’re blissfully unaware of the expensive ground they tread.
This one-mile stretch of the popular Cherry Creek Regional Trail, where bike commuters and joggers speed by in a nonstop parade, is nearing the end of a $16 million bottom-to-top rebuild. That’s more than $250 a linear inch.
Gok and her dog, Hugo, are fine with the pricey fix. They walk the creek starting at Monaco Parkway nearly every evening. In the mile upstream from Quebec to Iliff Avenue, they had watched the creek dig deeper and deeper into the channel, had seen the bike path hang precariously over undercut banks, and had watched the vegetation slowly melt down the banks and choke the stream.
“It was a big canyon,” Gok said at the end of a recent sweltering Colorado evening, spreading her arms northwest toward Quebec and southeast toward Cherry Creek Dam.
Frequent users like Gok are exactly right, responds Barbara Chongtoua, the engineer and driving force behind Mile High Flood District’s wrangling of six different agencies to make this one-mile overhaul work.
She’ll even go Gok one better.
“It was a mini-Grand Canyon,” laughs Chongtoua, who said the mile of Cherry Creek from Iliff downstream to Quebec represents the one stretch of the 40-mile trail from downtown Denver to Franktown in need of complete excavation.
Eventually, the meandering trail will stretch a few more miles to Castlewood Canyon State Park. It was a Native American traveling route, for the water and the fish and wildlife on the banks, and then an incoming pioneer route during the gold rush. It was one of the first key spokes in metro Denver’s bike trail hub radiating from Confluence Park.
Water cuts canyons for a living. In dense urban and suburban areas like Cherry Creek Drive South, engineers protecting expensive open space, bike paths, bridges and roadways need to find water a new job. Over the years, the creek in this area, when running high, created riffles that splashed water up and then down hard on the muddy channel bottom, creating washboards like cars on a gravel road. Each new high water period sent the splashes higher and the falling water digging deeper into the mud. The channel eventually gouged itself up to 20 feet below the top of the banks.
“If you were driving Cherry Creek South, you couldn’t even see the water from your car, that’s how deep it had gotten,” Chongtoua said.
Denver Water, Denver Parks & Recreation and Arapahoe County Open Spaces all worried about losing valuable assets in mudslides of undercut banks. The ecology grew to be a mess as well. Shade trees tipped over. Native trees and shrubs used to sending roots down a few feet for water in a riparian transition zone no longer had straws long enough to drink. Runoff left little but sand, and opportunistic invasive species from bindweed to globe thistle.
“Nothing else from the Cherry Creek Dam to Confluence Park was that bad,” said Chongtoua. By 2017, it was time to turn a few references in a years-old master plan into a fully-funded proposal for a synchronized heavy-equipment dance along the notorious mile.
Starting at Quebec and heading to the southeast, the banks are now carefully graded and terraced away from the main channel. The channel itself has been shored up with massive boulders stuck in engineered steps to prevent dredging in future floods. A new walking-only path on the north bank will supplement the concrete bike path on the south bank, with new crossover bridges at four points along the mile. The earthwork wraps up in August or September.
Some planting has begun, though the final touch of large trees won’t happen until next year as landscapers check to see how the water table behaves after the repairs. Cottonwoods and native grasses that thrive on periodic flooding will go right next to the flow.
“There are grasses that like their feet wet, and grasses that like their feet dry,” Chongtoua said.
Above that, workers will pound in thousands of willow stakes cut from dense groves downstream of Quebec. The stakes sprout into bank-saving shrubs as they search for the water table. Cutting the willow from a short walk downstream lowers the carbon footprint of the whole project.
Above that transition zone, at the highest spots where the bikers and walkers go, will be non-native, shade-producing trees whose root systems don’t need the flooding.
It fell to Mile High Flood District to assemble the agencies overlapping the mile, and to find the money. Denver Water smoothed one of the trickier questions, Chongtoua said, by donating 10 acres of land to Denver Parks and Arapahoe County Open Space to manage as they saw fit after the earth movers leave. The money came from at least seven sources, with a large chunk from the Denver Urban Drainage and Flood Control District.
The meticulous plan is a vast improvement for one of the metro area’s most heavily used stream corridors, said Jeff Shoemaker, director of the nonprofit Greenway Foundation, long an organizer and promoter of metro river upgrades.
The separate soft-surface path for walkers is a big upgrade for those intimidated by the hard bike path, where commuters and hardcore trainers ignore the 15-mph rules, Shoemaker said. “It means my daughter and my granddaughters can enjoy Cherry Creek without having to look over their shoulder every three seconds,” he said.
The intersection at Quebec used to include garbage landfills, Shoemaker said. Digging there might have uncovered chaos or tantalizing artifacts, or both. Excavators did indeed remove tons of concrete rubble and waste, as well as old sewer and water pipes, Chongtoua said. Alas, no fascinating ancient human or dinosaur bones, or gold bullion from overturned Wells Fargo wagons.
The improvements to flood control and ecological diversity “are just marvelous,” Shoemaker said.
Shoemaker is even optimistic the one-mile stretch could host next-level fishing before too long, an elusive goal for either the mercurial Cherry Creek flows or the industry-challenged South Platte River corridor through central Denver. The waters in both major streams can do better than their reputation as carp havens, Shoemaker said, and the rebuilt mile of Cherry Creek could be a good example.
Chongtoua would only commit to a “nice try” when it comes to much more than crawdad fishing. The streamflow that engineers let out of Cherry Creek Dam, two and half miles southeast, ranges from “3 cubic feet per second to 100 cubic feet per second and sometimes back to zero,” she lamented.
Prize species like trout need steadier flows and deeper, cooler pools to thrive. The new stream section is capable, with pools built into the reshaped channel, but engineers and conservationists would somehow have to negotiate stronger, steadier flows of fresh water.
In the meantime, visitors like Gok and Hugo are already finding their way into the spruced up corridor, oblivious to the orange hurricane fencing meant to keep them out. Gok’s only concern is that no one let the houses that are set back from the north bank creep any closer into the precious open space.
“We live in Cherry Creek North and come over here for this,” said Gok, trying to wrestle a 6-foot-long stick from Hugo’s resolute jaws. “Because Cherry Creek doesn’t even have a little park.”