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St. Vrain Creek Restoration: Phase 2
Reach 3 Phase 2

St. Vrain Creek Restoration (Reach 3): Phase 2

Project Completed

Restoration work has been completed and is now in the warranty, permit monitoring, and adaptive management phase. The location is along the St. Vrain Creek south of SH-66 between Union Road and N. 63rd Street and near the old “Breach 2” from the 2013 floods. The project created improved aquatic and riparian habitat while protecting infrastructure through enhanced floodplain connections and directing excess stream flow into improved main channel riffle and pool features. The diversion structure was made more robust through the use of buried sheet pile and the removal of a small dam feature was realized to enhance sediment and fish passage.

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 the upper bypass structure which was a 4-ft rock push-up 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.

Miscellaneous work areas upstream included:

  • Floodplain connectivity grading work and flood overtopping protection between Breach 2 and the upper bypass structure intersection.
  • Reworking 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.

St. Vrain Creek Reach 3 Phase 2 Project Area Map

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 including stream sweeping, 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.

Construction Schedule

  • Mobilization: Late July 2020
  • Breaking Ground: Early August 2020
  • Re-vegetation: October 2020-April 2021
  • Warranty Period: April 2021-April 2022
  • Adaptive Management and Vegetation Establishment Monitoring: 2021-2023

Project Background

Boulder County Parks & Open Space, along with the St. Vrain Creek Coalition, neighbors, and other stakeholders, collaborated on post-flood restoration planning for Reach 3 in the St. Vrain Creek Watershed Master Plan.

Parks & Open Space began planning and design work on Reach 3 of the St. Vrain Creek in 2016. The planning phase was funded by the HUD CDBG-DR and was a collaborative effort with stakeholders throughout the Saint Vrain Creek watershed.

Through a series of public meetings with neighbors, the City of Longmont, the St. Vrain Creek Coalition, and other stakeholders, the Engineering Analytics, Inc. design team developed a comprehensive plan and a 30% design.

Parks & Open Space then sought and received a grant from the Emergency Watershed Protection (EWP) Program of the Natural Resource Conservation Service (NRCS) as administered by the Colorado Water Conservation Board (CWCB). Utilizing this funding source, the 80% design for Reach 3 was completed by Engineering Analytics, Inc. in June 2017. American Civil Constructors LLC dba ACC Mountain West initiated construction in November 2017. Phase I construction was completed in May 2018. A small portion of the construction scope was removed during the initial contracting agreement discussions due to the need to engage ditch stakeholders in more depth. The removed portions eventually became the Reach 3 Phase 2 project as described above.

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Parks & Open Space

Sharla Benjamin