Something out of the ordinary is happening on one of Oregon’s rivers.
One of the state’s hydroelectric power plants stopped generating electricity in July and will remain offline for four months. The water flowing into the facility has not stopped moving. Instead of generating electricity through turbine blades, it is being directed over the dam’s spillway and sent downstream.
The shutdown is not the result of drought, equipment problems, or maintenance work.
EWEB says the change is intended to provide a safer route for migrating fish and bull trout moving through the McKenzie River system.
A new path for fish for the season
The Trail Bridge Powerhouse is located on the upper McKenzie River and is part of EWEB’s Carmen-Smith Hydroelectric Project. However, during the seasonal shutdown, the utility is directing water over the spillway instead of through turbines.
EWEB states that the operation provides a safe pathway for juvenile fish migrating from above Trail Bridge Dam into the remainder of the McKenzie River.
According to the utility, the change improves downstream passage for young fish.
Trail Bridge Dam marks the most upstream point that fish can naturally travel on the McKenzie River. Upstream of Trail Bridge Dam, only a limited amount of habitat exists before fish encounter Tamolitch Falls, a natural barrier that fish cannot pass.
While normally the water would flow through turbines, power generation has been temporarily halted so that adult bull trout may continue their migration downstream unimpeded.
The power tradeoff: How big of a deal is it?
It should be noted that Trail Bridge contributes little to the total electrical output generated by EWEB’s Carmen-Smith Hydroelectric Project. Trail Bridge has an installed capacity of approximately nine megawatts, according to EWEB.
By comparison, the adjacent Carmen Powerhouse has a maximum installed capacity of 110 megawatts and continues to operate while Trail Bridge remains offline.
The decision to conduct a “full spill” during peak summer months was not made voluntarily. According to EWEB officials, FERC requires them to do so under provisions contained within their current license to operate the hydropower project.
The requirement emerged through the relicensing process and is intended to reduce impacts on fish populations.
Lisa Krentz, Chief Electric Operations Officer at EWEB, explained how her agency balances the need for fish passage with the need to produce clean renewable energy: “The goal is to give young fish an easier pathway to connect to the rest of the McKenzie,” she said.
Additionally, Krentz said carbon-free hydropower remains important for meeting community climate goals and that finding a balance between fish passage and clean energy remains critical.
A glimpse of what comes next after a temporary shutdown
This short-term shutdown is but one component of a long-term plan to improve fish passage throughout the entire Carmen-Smith Hydroelectric System. EWEB is collaborating with regulatory agencies responsible for fisheries management regarding construction of a permanent trap-and-haul facility below Trail Bridge Dam.
The facility would move adult salmon and bull trout upstream while replacing temporary fish-passage measures currently in use.
Additionally, the utility plans to spend $24 million to build a permanent downstream fish passage facility at Trail Bridge. The new facility is intended to provide a longer-term solution for fish moving through this section of the river.
According to EWEB, once the permanent trap-and-haul facility becomes operational, nearly all power generation at the Trail Bridge Powerhouse will cease under the terms of its federal license.
For now, however, water that would normally be used to generate electricity is serving a different purpose.
Instead of passing through turbines, it is helping fish reconnect with the rest of the river system.
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