In April 2016, the City began a project to evaluate the possibility of reducing flood risks immediately up and downstream of Highway 287 (Lincoln Avenue) crossing of the Big Thompson River. This is a long-standing problem area brought to a critical level by the 2013 Flood.
The purpose of the study is to determine the level of improvements needed to maximize benefits in this area of the Big Thompson River at a reasonable cost. It will also provide recommendation to elected officials whether the City and Colorado Department of Transportation (CDOT) should move forward to replace the Highway 287 Bridge. It is the next step taken from the Hwy 287 Strategic Plan, which contained feedback from many businesses and citizens in the area.
The project was partially funded by a $125,000 Community Development Block Grant – Disaster Recovery (CDBG-DR) planning grant administered by the State of Colorado’s Department of Local Affairs (DOLA).
Goals of the project included:
- Changing the direction of infrastructure and land use decisions based on long term resiliency, maximizing benefits while minimizing long term costs
- Improve life safety and emergency access
- Reduce impacts and economic hardships to local businesses during a flood
- Restore natural river and floodplain functions where there currently are none
- Use the opportunity to create a more natural and beautiful riparian corridor
- Improve water quality
- Create a sustainable and stable environment for future community and business development.
The Highway 287 Flood Mitigation Feasibility Study was finalized on March 17, 2017, and was incoprorated into the City's recent Big Thompson River Corridor Master Plan. The study showed replacing the bridge with a new 240-foot span structure and significantly improving the river’s floodplain capacity up and downstream of the bridge are both necessary in order to provide a substantial reduction in flood risk. Replacing the bridge is necessary, but it has little value on its own without also constructing floodplain capacity improvements.
The proposed project would:
- Remove 47 insurable structures from the floodplain
- Remove 23 from the floodway
- Increase the development potential for 43 properties
- Allow for 20,000 cubic feet per second (cfs) to flow under the new bridge (the current bridge capacity is only 4,500 cfs)
- Prevent over topping of Highway 287 in a 100-year flood event.
The total cost, in 2017 dollars, was estimated at $16.9 million, including design, permitting, right-of-way/easement acquisition, construction, expected inflation, and a 25 percent contingency. The project was listed in the top five priorities in the Big Thompson River Corridor Master Plan.