PGE project allows fish on the Clackamas River to rock on
Every other September, an amount of gravel approximately the size of Sandy Public Library is transported to the banks of the Clackamas River near the River Mill Dam.
"We spent a lot of time thinking about how to do it," said Tim Shibahara, Westside Biological Services Manager for Portland General Electric, noting that the project at the River Mill site uses approximately 28,000 tons of gravel to enhance what was previously bare bedrock. "It emulates what the river does and captures it from the banks during flood events."
Teams at PGE add gravel downstream from the River Mill, Timothy Lake and Lake Harriet dams to enhance habitats for fish, including salmon, steelhead and trout. Because dams typically stop the flow of gravel downriver, the project creates beneficial areas for the animals.
"It impacts where the fish can spawn," Shibahara explained.
Near the Oak Grove fork of the Clackamas River, 500 tons of gravel were placed at Lake Harriet and 90 tons were placed at Timothy Lake last month.
Both of these sites present unique considerations when receiving their annual amounts of gravel. For example, Timothy Lake requires finer sizes of gravel because of the size of its fish, and Lake Harriet has steep canyon walls that teams must navigate when adding the gravel.
Staff at PGE said that this is the only gravel augmentation program they're aware of that specifically targets cutthroat trout conservation.
"For cutthroat trout, gravel is a very critical material for spawning habitats. There are limited amounts in that upper area," said Shibahara, adding that the healthiest population in the Clackamas River is between the Timothy and Harriet dams because they are isolated from the rest of the fish.
The gravel project, which began in 2016, is part of PGE's most recent license with the Federal Energy Regulatory Commission (FERC), which allows them to operate hydroelectric projects on the river and requires a 97% survival rate for fish. Additional work under the license has included adding a surface collector at North Fork Reservoir, a fish ladder at River Mill Dam, sorting facilities for both juvenile and adult fish and extending a fish pipeline.
"The response from the spawning was very dramatic. You could see it right away," Shibahara said. "All fish have benefited."
Along with supporting fish, the projects have also presented benefits for those visiting the river for recreation. Multiple log jams on the Clackamas that create habitats for salmon have been appreciated by people seeking adventure on the water.
"The stand-up paddle boarders and kayakers love that stuff. It creates a complexity that's fun to discover," Shibahara said.
He described the work as a river health project.
"It's like a quick shot in the arm," he said. "We'll analyze how the river utilizes the gravel and then set a new amount. We'll adjust going into the future."
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