The U.S. Forest Service has finalized the details of a repair project intended to reduce the risk of a disastrous release of mud and sediment from Spirit Lake, which after the 1980 Mount St. Helens eruption was blocked by a natural dam of debris.
The project has drawn controversy about plans for a 3.4-mile temporary access road across the Pumice Plain that researchers and conservationists say would disrupt a sensitive area that is the site of numerous scientific studies about the remarkable ecological resurgence of the past 40 years.
The work involves replacing an aging gate that regulates water flows through a tunnel providing critical drainage for the water backed up behind the Spirit Lake debris dam. The project also includes drilling to better assess the stability of the debris dam, which if it failed would threaten people and property in lowland drainages to the west, including the port of Longview.
“Citizens of these communities are living and working downstream from a poorly understood natural debris blockage that utilizes a dated tunnel outlet … that is subject to failure,” stated Gifford Pinchot National Forest Supervisor Eric Veach in the project’s record of decision.
The project is expected to start this summer and take up to four years to complete, with the cost — just for the gate replacement — estimated at $10 million to $25 million, according to the Army Corps of Engineers. The need for the work stems from the profound changes wrought by the 1980 blast and is part of a longer-term and bigger effort to reduce the risks of floods to downstream areas with $3.65 billion in property value.
The eruption killed 57 people and unleashed a massive avalanche of debris, part of which raised the water level of Spirit Lake by 210 feet and blocked its natural outlet. In 1982, a temporary pumping station was installed to lower water levels. This was followed by construction of the 1.4-mile tunnel to divert water into Coldwater Creek.
The current gate will be replaced with a two-gate system with matching emergency gates and a new rack to hold back debris. The drilling work will provide new information about the makeup of the debris dam.
Opponents of the plan acknowledge the work needs to be done. But they say the Forest Service has not done enough to reduce the impacts on the Pumice Plain, which they are concerned could include the introduction of invasive species in an area that is supposed to receive special protection under the Mount St. Helens National Monument management plan.
They hoped an alternative plan could be developed, and also proposed sharply reducing traffic along the road, which although temporary, would be used to bring heavy equipment into the work site.
“The tunnel needs repair, but we have time to do it right, and without damaging this world-class treasure that is Mount St. Helens,” said Charlie Raines, of the Washington chapter of the Sierra Club. “There are ways of doing this without punching a road across the Pumice Plain. For a place as extraordinary as this, we need to take extraordinary measures to do necessary work.”
Raines said that his group is still looking at ways to protect the area, which could include legal action.
Forest Service and Army Corps of Engineers officials say a range of options were considered.
They considered using helicopters to reach the site but found that would be costly, create safety risks due to the extensive mountain flying and would likely mean having to break equipment down, fly it in, then reassemble it on site in a process that would consume much of the warm-weather work season.
An alternative access route from the Johnston Ridge Observatory also was reviewed. But a Forest Service document states the equipment needed to replace the tunnel intake gate would not make it to the work site on that route.
“I recognize that this decision may have short- and long-term consequences to some of the research occurring on the Pumice Plain,” Veach wrote in the record of decision. “My team and I have made every effort to design a project that reflects a
balance between public safety concerns and effects to ongoing research.”
Thirty studies are now being conducted within the Pumice Plain, involving 992 research plots, 25 of which would be directly impacted by the road and include avian, amphibian and stream ecology, according to an environmental assessment document. Critics say more could have been done to protect these sites and reduce traffic on the temporary road that will make restoration difficult.
“Some of these are long-term research projects. Scientists are now retiring and handing them over to the next generation. We are talking about legacy work,” said Susan Saul, a Vancouver, Washington, conservationist who worked to establish the monument protections for the Mount St. Helens area.
In the years ahead, there will be more decisions to be made about how to proceed with work to reduce the risks from the debris dam.
Scientists who worked on a 2017 National Academies of Sciences Engineering and Medicine study of the mudflow risks found that the aging tunnel, despite repeated repairs, “is not operating optimally.” Their report suggested engineering options such as building a second tunnel or cutting a spillway through the debris dam.