Editor’s note: This article first appeared in Lower Columbia Currents, which reports news and opinion about Southwest Washington. It is published, reported and written by award-winning journalist Andre Stepankowsky. Learn more and subscribe by visiting the Lower Columbia Currents Substack.
A new federal plan would lower Spirit Lake 40 feet, construct a second drainage tunnel and repair an existing one as a hedge against future catastrophic flooding.
The plan would cost hundreds of millions of dollars and would drastically change the appearance and ecology of the iconic lake, perhaps dividing it in two, which is the reason some researchers oppose lowering it.
The U.S. Forest Service Tuesday released a final environmental impact statement that outlines a plan to prevent the lake from rising and breaching the mass of volcanic debris that blocked its outlet during the eruption of Mount St. Helens 46 years ago.
“This is a significant milestone in our work to protect downstream communities, reduce future flood risk, and strengthen the long‑term resilience of the Mount St. Helens landscape,” Johanna Kovarik, supervisor of the Gifford Pinchot National Forest, said in a prepared statement.
Congress will have to approve money to pay for the projects outlined in the plan.
If the lake were to rise and breach the blockage, scientists say the ensuing flood would cause catastrophic damage along the Toutle, Cowlitz and Columbia rivers. (See more on this, below.)
Under the plan, the Forest Service would repair the existing 8,500-foot-long, 11-foot wide drainage tunnel the U.S. Army Corps of Engineers cut through Harry’s Ridge. It allows the lake to drain into South Coldwater Creek and eventually into the north fork of the Toutle River.
However, the tunnel cuts through a 300-foot-wide fault and has needed repairs since opening in 1985.
“The tunnel has shown signs of age‑related deterioration, including rock heaving and structural cracking, increasing maintenance needs and long‑term risk. While still functional, it requires rehabilitation to continue serving its role effectively into the future,” according to the Forest Service.
The plan also includes construction of a new “pressurized” tunnel near the existing conduit to serve as the lake’s new primary outlet. The old tunnel would be the backup.
A pressured underground conduit is completely filled with water to allow pressure — as opposed to gravity— to push water through.
Under the plan, the Forest Service would lower the lake from its current elevation — 3,440 feet — down to 3,400 feet — to increase safe water storage capacity in case of a tunnel failure. The lake is considered safe as long as it does not rise above 3,460 feet, a level the lake has reached on three occasions.
The EIS also calls for building a permanent access route across the Pumice Plain on the south shore of Spirit Lake along the Truman Trail alignment and constructing a temporary haul route.
The Forest Service also says it will further study an idea to reconnect Spirit Lake directly into the North Fork Toutle River through a natural habitat channel.
Such a project would cost hundreds of millions of dollars and involve a risk of crossing unstable ground at the foot of a frequently-active volcano. However, it would raise the possibility of enabling salmon and steelhead to migrate naturally back to the lake.
The basic plan is little changed from a draft environmental impact statement the Forest Service released last year. The agency considered multiple options before settling on the one outlined in the final EIS.
The cost of the preferred plan is estimated roughly at $265 million — $53 million to rehab the existing tunnel and $215 million for the new pressure tunnel. This does not include the cost of creating a new natural channel across the debris blockage.
Spirit Lake is within the 110,000-acre Mount St. Helens National Volcanic Monument, which Congress created in 1982 to protect natural processes in part of the area blasted by Mount St. Helens on May 18, 1980. The legislation allows work to protect public safety, but the Forest Service has often found its management of the area caught in a pinch between ecological and human safety concerns.
It said it has tried to balance all the competing needs of research, recreation and flood control.
“The Spirit Lake Outflow Safety Improvement Project identifies a reliable long‑term solution for managing lake water levels while balancing ecological, cultural, and operational needs,” the agency said.
The Forest Service consulted a wide range of local officials, the Cowlitz Indian Tribe and other interest groups in developing the plan. The massive document is available online at https://tinyurl.com/nhzxphcr. The plan is subject to a 60-day public comment period.
Flood by the numbers
This article first appeared in Lower Columbia Currents, which reports news and opinion about Southwest Washington. It is published, reported and written by award-winning journalist Andre Stepankowsky. Learn more and subscribe by visiting the Lower Columbia Currents Substack.
