Nine water providers along Colorado’s Front Range formed the Chatfield Reservoir Mitigation Company (CRMC) to address the critical need for water storage for agriculture and a growing population. They were united by a goal of reallocating 20,600 acre-feet of space in a U.S. Army Corps of Engineers (USACE) reservoir at Chatfield State Park (the Park). The USACE determined that the reservoir could accommodate an additional 12 feet of renewable water supply storage without compromising the flood control for which it was designed. However, this increase in water levels from the Chatfield Mitigation Project (the Project) was anticipated to create impacts to the riparian environment around the reservoir. CRMC hired Muller to develop plans to mitigate the environmental impacts.

When Muller’s team assessed the Project area, they discovered catastrophic degradation from growing geomorphic instability and flood damage along Plum Creek and the South Platte River that threatened the existing rich riparian environment along the waterways within the Park. Working together with USACE and Park staff, Muller and the water suppliers responded with an unprecedented and innovative approach, reoriented the mitigation concept presented in the Environmental Impact Statement (EIS), and committed to a massive design and construction effort to restore the damaged stream systems, thereby protecting hundreds of acres of existing pristine riparian wetlands from further degradation.

To provide a healthier functioning system, enhance the riparian habitat, and dissipate flow energy naturally, Muller’s design incorporated riffle-pool stream complexes, natural meandering planforms, and restored secondary channels that reconnected streams to their floodplains and rehydrated adjacent wetland benches.

The EIS estimated that only 10% of the required environmental mitigation could be accomplished within the Park and 90% off-site, a difficult and expensive endeavor that would leave the Park with the smaller share of environmental enhancement. Muller offered an innovative approach that satisfied 85% of the environmental mitigation requirements within the Park with a natural design that is sustainable, cost effective, and reduces long-term maintenance requirements. The completed Project will deliver a renewable source of water to municipal and agricultural users for generations to come.