COLORADO SPRINGS, CO – Excessive erosion of the Cottonwood Creek channel in Colorado Springs threatened two arch culverts below an old railroad bridge, a sewer line and a vital $10 million CenturyLink telecommunications facility.
The city decided to initiate a restoration and stabilization project to eliminate the threat.
In 2011, Colorado Springs applied for funding through the FEMA’s Pre-Disaster Mitigation (PDM) program to address bank stability and the privately-owned telecommunications facility, and to protect the exposed sewer line and provide critical stream floor stabilization.
The project also contributed to development of a much larger master plan. Cottonwood Creek is a tributary of the Fountain Creek Watershed. One of the goals of the Fountain Creek Corridor Master Plan is to improve water quality and watershed health by reducing erosion, sedimentation and flooding.
Before the project could move forward, a few historic bridges needed some consideration. Both the Old Railroad Bridge and the Vincent Drive Bridge are listed on the National Register of Historic Places. The Old Railroad Bridge, a massive two-span masonry arch structure constructed in 1887, supports a 10-ft. deep fill that once carried a track of the Santa Fe Railroad.
Prior to funding the project, FEMA required an Environmental Assessment including opportunities for public input to make sure the project would not violate any portion of the National Environmental Policy Act.
The cost of the mitigation project was $4.3 million. FEMA provided a grant of $3 million.
The project included the construction of concrete structures slowing the flow of water through the creek, stabilizing the floor of the channel to prevent erosion around the Old Railroad Bridge piers and buried utilities. Concrete was placed around the piers of the Vincent Drive Bridge to provide additional support. The channel lining and concrete structures were designed to slow the erosive floodwaters and protect the channel floor and slopes.
The project was a cooperative effort of the city of Colorado Springs, Colorado Springs Utilities and the affected property owners and their engineers.
The City of Colorado Springs Engineering and Street Divisions were responsible for overall project administration, project design and construction management.
Specifically, the design provided:
- Emergency access via a maintenance trail along this segment of the creek that can also serve as a regional trail connection;
- Concrete structures that slow the flow of water through the creek, stabilize the bottom of the channel and prevent future erosion around the bridge piers; and
- Concrete lining on the bottom of arch culverts to channel bank riprap lining and side slope stabilization.
For additional information, visit: http://www.springsgov.com and http://www.fema.gov/environmental-planning-and-historic-preservation-program/nationwide-programmatic-environmental.