Updated: June 18, 2014 at 8:28 pm
People living in neighborhoods below the Flying W Ranch in western Colorado Springs can breathe at least a small sigh of relief.
Tim Mitros, the stormwater manager for the City of Colorado Springs, showed off the latest flood mitigation project Wednesday, unveiling a large sediment detention basin along North Douglas Creek that should keep tons of water, mud and bigger debris from invading residential areas.
The basin will hold about 25,000 cubic yards of sediment and can be cleaned out after each torrential storm, Mitros said. The new pond replaces a series of five smaller basins that filled quickly in early September 2013 after torrential rains pounded the Waldo Canyon fire burn scar and the rest of the Front Range from El Paso County to the Wyoming border.
"It was supposed to be a 10-year fix," Mitros said, noting that the city was surprised at how quickly the smaller basins filled and knew it had to come up with a Plan-B.
Now when water and debris come raging down North Douglas Creek the large pond should stop most of the flow. And an "alluvial fan" below the basin will likely slow the water and spread out the rest of the torrent before it reaches the city's storm sewers, Mitros said.
Mitros and Flying W Ranch Foundation executive director Aaron Winter are relieved that the project has been completed before the 2014 monsoon season and potential heavy thunderstorms hit the burn scar. Storms in early July, mid-August and September of 2013 threatened North Douglas Creek and left Manitou Springs cleaning up after flash floods poured over U.S. Highway 24, out of Williams Canyon, destroyed multiple homes and flooded businesses along Manitou Avenue.
"There is a lot of debris that is staging in the upper parts of North Douglas Creek," Mitros said. "We expect in larger storms that the debris will start to flush out."
According to the city official, an estimated 60,000 to 100,000 cubic yards of mud and debris are sitting along the creek less than a mile above the new detention basin. He said it took just about 60,000 cubic yards to fill the five smaller ponds.
Winter said the work that the city has done, as well as other projects by volunteers with the Coalition for the Upper South Platte, have helped reassure the foundation that its neighbors to the east will be protected.
"Knowing that this basin is in place to protect the homes downstream is a big weight off our shoulders," he said.
Hundreds of volunteers with CUSP have scoured the nearly 2,000-acre Flying W property over the last two years reseeding the slopes and building log erosion barriers, Winter said.
Another larger basin is also being built on the northeast sector at the Garden of the Gods Park along the Camp Creek channel.
That basin will also be able to be cleaned out, Mitros said. But that project will not be ready until at least July 4. It was also prompted by the September floods, in which tons of mud and other debris poured through the Glen Eyrie campus and came to rest in the area where the pond is being built.
The North Douglas Creek project costs about $300,000 and the work being done at Garden of the Gods carries a price tag of $200,000 Mitros said. The money is being provided by the city and the federal Emergency Watershed Protection Program. The EWP pays 75 percent of the cost and the city funds the other 25 percent.
As for the cleanup after storm, Mitros said that will be done by the Colorado Springs Street Division and come from the general budget.
"We're trying to make it as cost effective as we can," he said.