Leggett Creek Culvert Replacement

An existing culvert did not match the upstream stream width and had a damaged inlet which caused excessive velocities, debris jams, and the lack of continuous substrate inside the culvert. The 9-foot round culvert was removed and a 20-foot wide open bottom multi-plate arch culvert was installed. The new wider structure including natural stream substrate, grade control weirs, and streambanks inside the culvert will allow passage for all life stages of fish as well as passage for all for aquatic organisms. Installation of the bottomless pipe arch including full stream width inside the culvert with natural stream substrate and grade control weirs reduces stream velocities, concentrates flow at low flows, creates lower velocity resting areas during passage, and near margin passage opportunities. Approximately 7.98 miles of stream were made accessible for both adult and juvenile steelhead which are present in Leggett Creek.

There were minimal variations regarding the work that was between the proposed project and the final project. The project was implemented as we designed with one change order due to encountering unsuitable foundation material which had to be removed and replaced with suitable material.

Reported spent match funds were significantly more than proposed match funds. This was a result of the project sponsor only reporting the minimum required match (33%) for the proposal instead of the total anticipated cost. Upon completion, all funds spent were reported.

Update: The installation of the new culvert has achieved its goals and the fish are benefiting through passage to approximately 7.98 miles accessible rearing and spawning habitat.

This project will restore fish passage to 7.98 miles of stream for ESA-listed South Fork Clearwater River population of the Clearwater Major Population Group of the Snake River steelhead Distinct Population Segment into the Leggett Creek watershed by replacing the dysfunctional and undersized culvert at the confluence of the creek with the South Fork Clearwater River. The existing culvert also has a damaged inlet that alters flow of water at high velocities and causes debris to jam the inlet.

The existing culvert fails to pass adult steelhead and juvenile steelhead at most flows due to excessive inside-pipe velocities and the absence of fish passage structures to aid fish movement. The culvert is a partial barrier to Chinook salmon, ESA-listed adult bull trout, westslope cutthroat and Pacific lamprey (historically present in the watershed).
A known ESA- listed steelhead presence exists in the lower 5 miles of Leggett Creek. Steelhead habitat potential was classified as ‘Very High’ in the lower 5 miles of Leggett and ‘High’ in the upper reaches creating a historic stronghold for Steelhead trout. The lower reaches of Leggett Creek is a historic stronghold for ESA-listed bull trout with a very high habitat potential. There is a known presence of spring Chinook in this reach and is also categorized as historic stronghold with a very high habitat potential.

This project addresses limiting factors identified in the Proposed NMFS Recovery Plan (2015) for the South Fork Clearwater River steelhead population and implements action recommended by the plan to improve steelhead productivity.