Study in Progress

Long-term Management of the Spirit Lake/Toutle River System in Southwest Washington



The 1980 eruption of Mount St. Helens sent out an avalanche of debris and volcanic deposits that blocked the natural flow of water from Spirit Lake to the Toutle River in in southwest Washington state, causing long-term changes to the watershed's hydrology. A 1.5 mile tunnel was constructed to control water levels in the lake and avoid a catastrophic failure of the blockage which could result in a release of large quantities of water and sediments into the watershed that would pose a threat to 50,000 residents. Recent inspections revealed the tunnel is at risk of failure, and emergency repairs are underway. However a long-term solution is sought for management of Spirit Lake and the Toutle River system. This study will produce a decision framework for that management.

Public meetings will provide opportunity for stakeholder identification and input. The study committee will not make recommendations regarding the best engineering solutions, but rather will identify gaps in information and recommend framework for decision-making by the U.S. Forest Service and other infrastructure owners in the region.

About the National Academies of Sciences, Engineering, and Medicine Study Process




(all input will be posted in the public access folder)

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Meetings

Meeting 1: Long-term Management of the Spirit Lake/Toutle River System in Southwest Washington - 06/21/16
Meeting 2: Long-term Management of the Spirit Lake/Toutle River System in Southwest Washington - 08/03/16
Meeting 3: Long-term Management of the Spirit Lake/Toutle River System in Southwest Washington - 10/31/16 - 10/31/16

Statement of Task

An ad hoc committee of the National Academies of Sciences, Engineering, and Medicine will recommend a framework for technical decision making related to long-term management of risks related to the Spirit Lake/Toutle River system in light of the different priorities of federal, tribal, state, relevant local authorities, and other entities. The framework will incorporate the best available science and engineering and take into consideration regional economic, cultural, and societal priorities. The framework will also take into account the respective roles of stakeholders regarding management of the Spirit Lake/Toutle River system. The multiple objectives of enhanced safety of the downstream communities and the protection of the local and regional ecology and economic activities will be integral to the framework. The history of characterization, monitoring, and management associated with the Spirit Lake debris blockage and tunnel, other efforts to control outflow of water and deposits from the 1980 debris avalanche, and the risk of failure of the debris blockage will inform committee findings and recommendations.

The committee will:
* consider the adequacy of existing information and risk analyses for the area;
* suggest additional information needed to support implementation of the decision framework; and
* identify possible alternatives for long-term management of water levels and sediment transport in the Spirit Lake/Toutle River system.

The report will inform a quantitative examination of the viability of long-term management options by the U.S. Forest Service.