Tunnel near Mount St. Helens needs work to avert flood risks
SEATTLE — Long-term strategies are needed to deal with the risks of mudflows and flooding left behind by the 1980 Mount St. Helens eruption, according to a report by the National Academies of Sciences, Engineering and Medicine.
The most serious threat is at Spirit Lake, which the volcano left plugged by an unstable mass of debris that — if it gave way — would threaten some 50,000 Southwest Washington residents who live downstream.
A drainage tunnel completed in 1985 reduces the chance that the makeshift dam could fail. But the report found that the aging structure — despite repeated repairs — “is not operating optimally,” and is still in need of expensive maintenance.
The scientists who put together the report suggest future engineering options, such as building a second tunnel, cutting a spillway through the debris dam or finding a way to drain the lake. They propose a collaborative effort that brings together federal and state agencies, the Cowlitz Tribe, downstream communities and others.