From The Pueblo Chieftain (Chris Woodka):
It was a massive task. The question was simple: What are the impacts of building dams at various points on Fountain Creek? To do that, the U.S. Geological Survey broke the 932-square-mile drainage area into 72 subbasins, looked at 1,900 cross-sections and relied on historic information from more than a dozen stream gauges. “We used the information that was available, but engineers always want more information,” David Mau, head of the Pueblo USGS office, told the Fountain Creek Watershed Flood Control and Greenway District last week.
He was careful to point out that funding, property acquisition and water rights questions were not addressed by the study.
Mau released preliminary findings that show Pueblo would get equal protection from flooding by building one large dam or a series of 44 retention ponds along the creek. Most surprising was the relatively strong protection provided by just 10 detention ponds south of Colorado Springs. But the $570,000 study, expected to be finalized later this year, is just the beginning of protection for Pueblo from the highly variable and sometimes destructive flows of Fountain Creek. The political battles over stormwater still are being waged and the costs of alternatives largely unknown, but it is clear that building a series of smaller structures rather than a large earthen dam would cost less.
The district also must determine in the next few years how to spend $50 million coming to it from Colorado Springs as a condition of its 1041 land-use permit with [Pueblo County].
Four potential scenarios are among 14 modeled by the U.S. Geological Survey:
1. Build 44 detention ponds from the Air Force Academy to the confluence of Fountain Creek at the Arkansas River. Reduction of peak flows: 59%. Reduction of sediment: 18%.
2. Build an 85-foot earthen dam north of the confluence: Peak flows: 56%; sediment: 62%.
3. Build 10 detention ponds between Colorado Springs and Pueblo: Peak flows: 47%; sediment: 8%. 4. Build a diversion channel at the El Paso-Pueblo County line to channel flows into Chico Creek: Peak flows: 42.5%; sediment: 8.4%.
Numbers are based on a 100-year storm centered over downtown Colorado Springs. Peak discharge without any dams is 37,500 cubic feet per second, measured at Pueblo. Sediment load without any dams is 104,000 tons.