Boulder County is working with the Niwot Ditch Company and associated unincorporated ditches on the reconstruction of the Niwot Ditch in-stream diversion dam on St. Vrain Creek between 75th Street and Airport Road.
Niwot Ditch Diversion Repair & Fish Passage Installation Project
This structure is currently in a dilapidated state and vulnerable to structural failure during peak flows or high flow events. Additionally, the current structure creates a hydraulic jump in the creek, increasing potential for erosion and avulsion, creating a barrier to fish passage and disrupting important natural stream processes, such as sediment transport. This is a collaborative project which also includes the US Fish and Wildlife Service, Colorado Parks and Wildlife, and Trout Unlimited.
Wildlife Habitat Enhancements
This diversion dam is located on a reach of St. Vrain Creek that is one of that last strongholds for native transition zone fish in Colorado (e.g. plains top minnow) and is one of Colorado Parks and Wildlife’s highest priorities for native fish conservation in the state. One of the management goals for conservation of these sensitive native fish populations is to restore upstream-downstream connectivity and allow for natural movements of both native and non-native sport fish by removing instream barriers to movement. The primary goal of this project is to protect and restore native fish populations while ensuring the efficient delivery of decreed water rights.
The project includes ecological restoration elements designed to support native fish species by improving in-stream habitat conditions and reducing the stream gradient and velocity. The project will restore some geomorphic and hydrologic processes, improving the sediment transport capacity and providing for attenuation of flood flows within the stream reach. Planned restoration of wetland and riparian vegetation will benefit Preble’s meadow jumping mouse by providing habitat structure, improving habitat connectivity and enhancing production of insect prey and other food resources.
New Diversion Dam Structure
The project will replace the existing diversion dam with an engineered structure approximately 400 feet upstream of the existing dam location that includes two headgates. Using design concepts from natural channel design, the new diversion dam will be a multi-objective structure built from natural materials that is more resilient to high flows, reduces flood risk, allows passage of native and non-native fish, and facilitates natural stream processes and function.
The design and construction of the project are funded by US Fish and Wildlife Service National Fish Passage Program, Colorado Parks and Wildlife Wetland Grant, CWCB Species Conservation Trust Fund, Trout Unlimited, Community Development Block Grant – Disaster Recovery (CDBGDR), and Boulder County. Boulder County is also contributing native fill material in-kind from a flood recovery project and cut logs from a forestry project. The design has been developed by GEI Consultants Inc.
Initiation to Bid
Parks & Open Space is seeking bids from qualified and experienced contractors to secure construction services for the reconstruction and protection of ditch infrastructure, installation of a fish passage system, restoration of stream channel, stabilization of creek banks, and the re-vegetation of the area. Learn More →