Land & Resources Management

Spirit Lake Outflow and Tunnel

National Academies of Sciences, Engineering, Medicine Consensus Study Report: 

A Decision Framework For Managing The Spirit Lake And Toutle River System At Mount St. Helens

BACKGROUND – A massive debris flow during the 1980 eruption of Mount St. Helens created Castle and Coldwater lakes, and blocked the natural outflow from Spirit Lake. To maintain a safe water level in Spirit Lake, the U.S. Army Corps of Engineers (USACE) constructed a tunnel, completed in 1985 as a 1.6 mile, 11-ft diameter shaft bored horizontally through rock on the Mount St. Helens National Volcanic Monument. As the tunnel ages its components require repair and replacement, and total deferred maintenance is in the tens of millions. The NASEM report provides recommendations for improved understanding of options for long-term management of the outflow from Spirit Lake.

Spirit Lake - Tunnel constructed by U.S. Army Corps of Engineers in 1985
Coldwater Lake - Engineered channel constructed by U.S. Army Corps of Engineers in 1981
Castle Lake - Engineered channel constructed by U.S. Army Corps of Engineers in in 1981


SPIRIT LAKE PROJECT WORK – The Forest Service working with the USACE and U.S. Geological Survey completed critical repairs to a section of the tunnel, developed an emergency operations plan and held table top exercises, completed a risk assessment, installed a log debris barrier, added a new tunnel flow sensor in addition to other investments to reduce risk and improve safety.


                                 2016 WORK AT SPIRIT LAKE 

Critical Tunnel Repairs

Critical tunnel repairs

Log Blockage

Log debris

Log removal

Log debris removal


                                     2017 WORK AT SPIRIT LAKE

Road Access Work

Administrative road access improvements

Admis Improvement

Annual interagency tunnel inspection

Log barrier installation

Log debris barrier installation

Log Depris Barrier Install

Log debris barrier installation

Current Spirit Lake surface elevation

Mount St. Helens Volcanocam
Lakes and drainages around Mount St. Helens

The Geologic, geomorphic, & hydrologic context underlying options for long-term management of the Spirit Lake outlet near Mount St. Helens, WA.