Coaledo Tide Gate Replacement and Beaver Slough Fish Passage Project

The primary outcome of funding will be the purchase and installation of culvert/tide gate infrastructure. Three 8’x10’ tide gates will be mounted on side-hinges and controlled by MTRs to independently managing water levels. In addition, each gate will be equipped with a smaller 3’x3’ slide gate that can be opened independently. This outcome will result in improved fish passage to the basin and increased juvenile fish survival, notably for juvenile OC coho salmon.

The second component of this project will be channel enhancements downstream of the tide gates. Decades of a poorly functioning tide gate minimized tidal influence in Beaver Slough. Bathymetry surveys completed in 2019 and 2020 showed an unnaturally high level of sedimentation and a number of “high points” that would reduce the effectiveness of new infrastructure to mimic historical tidal fluctuations. The technical team chose to pursue the option that removed sediment (existing fill) from the 0.7-miles (approximately 3,020 cubic yards) of lower Beaver Slough but had the least amount of disturbance. Additionally, a dilapidated farm access bridge will be replaced and log boom will be removed during this process.

The Coquille River regularly reaches lethal temperature levels for salmonids in summer and has favored invasive predatory sport fish. Our project will develop a riparian buffer along both sides of the 1.25-miles in between the CVWA and the mainstem through planting native woody vegetation, at a density of 500 trees per acre and livestock fencing.

A major outcome of this project is the adjustment of the tide gate seasonally as guided by a WMP, which is agreed to by ODFW, the CDD, and regulatory agencies. The WMP was based on existing conditions, known fish use, and improved ecological function while not negatively impacting upstream landowners. The project will also greatly increase overall aquatic function through improved dissolved oxygen levels, thermal regimes, and greater tidal exchange of tidal inflow that can be allowed with slide gate and MTR tide gates. Adhering to the WMP will be a shared responsibility with ODFW and the CDD.

Funds will be used to continue implementation of the Coquille Sub-basin Plan and PCSRF Priority One, allowing the Tribe and its multiple partners to conduct a restoration and monitoring project within the lower Coquille River sub-basin. The project will seek to improve limiting factors for ESA listed Oregon Coast Coho (OC coho) salmon. The project specifically seeks to improve habitats through:

• Improvement of salmonid access to approximately 9,800-acres containing 11.4-miles of coho habitat and 490-acres of tidal wetland habitat.

• Replace the three top-hinged aging Coaledo tide gates with three side-hinged Muted Tidal Regulator (MTR) tide gates.

• Implement a Water Management Plan (WMP) that seasonally adjusts water levels.

• Complete channel enhancements which includes removal of unnaturally high sediment, replacing a farm access bridge, and removing a log boom in Lower Beaver Slough.

• Enhancing the riparian buffer of 2.5-miles, which will include fencing and planting.

• Improve water quality by restoring natural tidal fluctuations, reducing stream temperatures, and increasing dissolved oxygen.