The U.S. Forest Service is reviewing ways to prevent Spirit Lake from overflowing by updating or replacing an aging tunnel built to drain the lake after the 1980 Mount St. Helens eruption.
The plan aims to protect downstream communities from catastrophic floods, and may or may not use the intake gate the agency is replacing at the site today.
A virtual presentation this week broke down a handful of “long-term resilient solutions,” said project consultant Dan Tormey, including revamping the existing tunnel, building a new one that would have a greater flow rate, building a new pressurized tunnel and a couple open channel options.
Tormey, president of Catalyst Environmental Solutions, said the project would release its Draft Environmental Impact Statement early this summer, but could not provide a construction timeline. When an option is selected, the project would take between 3 and 10 years to complete, he added.
The Forest Service is also replacing the tunnel’s intake gate after the closure of a lawsuit aiming to prevent a road from being built through the post-eruption research to reach the site.
Work on that project started in 2024 and is expected to be completed in 2027, said Charles Lassiter, a spokesperson for Gifford Pinchot National Forest. The gate replacement fixes the structure nearing the end of its design life, but might not be used in the long-term solution the Forest Service is reviewing for the entire tunnel, he added.
The problem
The Forest Service’s Gifford Pinchot National Forest is responsible for managing the aging roughly one-and-a-half mile long tunnel.
Over time, its function has reduced, threatening to overwhelm the natural dam that holds back tens of billions of gallons of water and risking sending that water down the Toutle River Valley into cities where more than 50,000 people live.
The problem was created by Mount St. Helens’ 1980 eruption, which sent more than one million Olympic swimming pools worth of debris into the Upper Toutle Valley.
One consequence of that was debris blocked the giant lake’s natural outflow. The US Army Corps of Engineers built the tunnel in 1985 to drain the lake after various stop-gap measures. Over the years, the tunnel has needed substantial repairs in 1995, 1996 and 2015/16, said Tormey.
The possible solutions
Tormey said the most important factor of the project is to reduce risk to public safety. He said the project also is weighing concerns including the integrity of ongoing research in the area, environment and anadromous fish passage, the economy and local native nations’ interests.
The eventual project would likely combine multiple options to make sure there is both a primary and backup way for the lake to drain.
Tormey explained the potential pros and cons of each approach. The entirely machine-excavated channel option didn’t score high marks because it would require about a million dump truck loads to clear out the material and had high risks if the natural dam failed during the project.
A related option, however, seemed to score well. That approach would use a pressurized tunnel to lower levels of the lake and some excavation to start a channel for water to leave. But it would then let the water erode its own channel, leading to potential fish passage benefits.
Federal funding would cover the project, he said in response to a question by The Daily News. But he did not provide potential costs of the options.
Lassiter also said the project’s environmental reviews will take until 2026, then the project must select a plan before seeking funding. The funding component alone could take “several years or more,” he said.
The update on the Spirit Lake project came amid dramatic cuts at the Forest Service, including at Gifford Pinchot. Large federal-funded infrastructure projects now face an uncertain future as the Trump Administration slashes public services and investment – both locally and around the country.
Henry Brannan is a Murrow News Fellow shared between The Daily News and The Columbian, covering Columbia River economics and environment.
