From The Pueblo Chieftain (Chris Woodka):
To see how a dam on Fountain Creek might function, it isn’t necessary to look far.
For more than 30 years, three flood control dams have protected downtown Denver from flooding. The first was built on Cherry Creek in 1950, but when waters from the 1965 flood inundated Denver, two other dams, Chatfield and Bear Creek were also built by the U.S. Army Corps of Engineers.
Of the three, Bear Creek Lake is the most similar to the type that would be built on Fountain Creek.
The earthen dam, 1 mile long, was completed in 1982 and usually stores a relatively small amount of water, about 2,000 acre-feet. Most of the remaining area behind and around the dam is a city of Lakewood park, which offers camping, fishing, picnic areas, trails, archery ranges and golf courses. Other recreational lakes and wetlands are behind the dam.
But twice in the past three years, the dam has prevented millions of dollars of damage by holding back water in a 236-square-mile drainage area — its primary function.
“It reached a record level in 2013 and close to that level in 2015,” said Joe Maxwell, operations manager for the Corps. “There were no abnormalities found as we monitored and it performed as it should.”
Wall of water
In the September 2013 flood, the largest in Colorado’s recorded history, damage to numerous communities, highways and water structures was recorded. But Bear Creek, Chatfield and Cherry Creek kept it from being worse.
Bear Creek Lake stored 28,500 acre-feet of the wall of water that descended during the 2013 event, well within its capacity. The lake level reached an elevation of 5,607 feet, higher than ever before and 50 feet above normal. Water releases began even as other areas still registered high water, because of the Corps’ protocols for operating all three reservoirs in tandem. It took three to four weeks to empty the floodwater.
“The goal is to release the water as soon as possible, but you don’t want to release it too fast,” Maxwell said.
Repairs to trails, roads and structures in the park cost $372,000 and were newly complete last May, when sustained rains pounded the Front Range. Like other areas, Bear Creek Canyon had weeks of sustained rain, which surprised the Corps by filling Bear Creek Reservoir again. The level of the lake rose 50 feet, and didn’t drop to normal until the end of July.
Repairs the second time around in 2015 were less extensive, because there was more warning, a different type of flooding and lessons learned from 2013, said Drew Sprafke, Lakewood regional parks supervisor.
“It was a different character without the high flow in the creek,” he said. “It re-impacted some of the same area, but we had more notice and knew how to respond.”
The city of Lakewood didn’t have to foot the whole bill, but matched county, state and federal funds to make the repairs. But the inundation of water has changed the character of the park, Sprafke said.
“We were able to make repairs,” he said. “But we lost 300 trees that will have to be clear cut. It’s a massive change to the park. The trees were under water for 11-12 weeks in both events, and invasive weeds came in. It will take at least five to 10 years to recover.”
Fountain Creek outlook
A dam, or multiple dams, on Fountain Creek would function in much the same way and has been talked about for years as a way to protect Pueblo from flooding.
The first idea for a dam on Fountain Creek came as part of an Army Corps of Engineers study in 1970 following the flood of 1965. The dam was never funded, and levees on Fountain Creek were completed through the city of Pueblo instead.
A multipurpose dam was brought up again by Pueblo County’s water attorney, Ray Petros, in 2005 as a potential alternative for Southern Delivery System.
As sedimentation has diminished the effectiveness of the levees, the dam idea has been revived in recent years.
A study last year by Wright Water Engineers for Pueblo County showed that 370,000 tons of sediment are deposited south of Colorado Springs each year as flows into Fountain Creek increase. Much of that winds up in Pueblo, raising the level of Fountain Creek and decreasing the effectiveness of the levees.
A payment of $50 million toward flood control on Fountain Creek was written into Pueblo County’s 1041 permit for SDS, and a dam is central to studies.
The Fountain Creek Watershed Flood Control and Greenway District, formed in 2009 as an outgrowth of the Vision Task Force, funded a U.S. Geological Survey study of hypothetical dam sites in 2013. That study showed the most effective way to reduce peak discharge and capture sediment would be a large dam about 10 miles upstream from the confluence of Fountain Creek at the Arkansas River.
Another alternative would involve several detention ponds north of Pueblo, which would be nearly as effective in reducing peak flows, but would capture less sediment.
A study for the district last year by engineer Duane Helton showed negligible impact on downstream water rights if flood control structures maintained a flow of 10,000 cubic feet per second through Pueblo during all but the largest flood events.
The district is now preparing for more detailed feasibility studies that would show where structures could be located and how much they would cost.
That’s a long way from the parks and trails that Lakewood residents enjoy near their flood control dam, but the Fountain Creek district is committed to protecting the creek and topping it with increased recreational opportunities only as the areas along the creek are stabilized.
The district has spearheaded both flood control and recreation demonstration projects so far.