Managing the Spirit Lake and Toutle River System – New Report

The 1980 eruption of Mount St. Helens in Washington State resulted in a massive debris avalanche and volcanic deposits in the Toutle River valley.  Sediment deposited in the area blocked the flow of water from Spirit Lake and other nearby lakes to the Toutle River, causing radical changes to the long-term hydrology of area watersheds.  In order to protect the nearly 50,000 residents of the region, a 1.5-mile tunnel was constructed to control water levels in Spirit Lake and prevent a catastrophic failure of debris blockage, but recent inspections show that the tunnel is at risk of failure, and emergency repairs are underway.  

A Decision Framework for Managing the Spirit Lake and Toutle River System at Mount St. Helens, a new report from the National Academies of Sciences, Engineering, and Medicine, offers a framework to guide federal and state agencies, tribes, community groups, and other stakeholders in making decisions about the lake and river system.

The report will be available to reporters only starting at 2 p.m. EST on Thursday, Dec. 7.  The report is embargoed and not for public release before 11 a.m. EST on Friday, Dec. 8.  Reporters who wish to obtain copies should contact the Office of News and Public Information; tel. 202-334-2138 or e-mail

In early 2018, members of the committee that conducted the study and wrote the report will hold a public briefing in southwest Washington to discuss their findings and recommendations.