Phase 2 Overview
The Reach 3 Phase 2 (R3P2) project impacted 1,150 linear feet of St. Vrain Creek and provided a healthier stream channel that previously only received overtopping or leakage flow from upper bypass structure (small dam). The project reach included the upstream intersection of the St. Vrain Creek with the ditch supply channel for the Longmont Supply ditch and the Chapman & McCaslin ditch.
Other work areas upstream included:
- Floodplain connectivity grading work and flood overtopping protection between Breach 2 and the upper bypass structure intersection.
- Rreworking a small portion of the soon-to-be abandoned Baker & Weese ditch to shunt flood flows away from the previous work done for the Breach 2 repair which had been part of the Reach 3 Phase 1 (R3P1) project.
The intent of this project was to create a stable channel reach. The project concept was to re-design the existing upper bypass structure and downstream St. Vrain Creek channel to the intersection of the ditch supply channel return flow confluence. The project objectives included providing more continuous sediment transport and fish passage in the St. Vrain Creek channel, moving high energy water away from local ditch headgates, providing the decreed flows to the local ditches as first priority, and mitigating future flood damage on local and downstream properties.
Additional objectives of this project included increasing floodplain connectivity to reduce the power of flood flows; increasing stream resiliency to recover from flood flows; incorporating native plant revegetation to support Preble’s Meadow Jumping Mouse (PMJM, Zapus hudsonius preblei); and using vegetation, habitat boulders and large wood to stabilize soils, increase channel and floodplain roughness, and increase topographic complexity.
The stream restoration approach and the ditch infrastructure protection targets are consistent with the larger vision for watershed and stream recovery as proposed within the St. Vrain Creek Watershed Master Plan.
Zak Dirt was the Contractor for this project, with Western States Reclamation as sub-Contractor for the vegetation installation.
Design work started in June 2019. The design team was led by Otak, Inc. with sub-consultants Ecos, Michael Baker International, Wright Water Engineers, King Surveyors, and Yeh & Associates.
Funding was provided by the U.S. Department of Housing and Urban Development’s Community Development Block Grant Disaster Recovery Program (HUD CDBG-DR) administered by the Colorado Department of Local Affairs and the Boulder County Collaborative.