The eruption of Mount St. Helens in the spring of 1980 caused a large movement of sediment into surrounding rivers, threatening downstream communities in southwestern Washington with flooding.
Following the eruption, the U.S. Army Corps of Engineers, Portland District, implemented several strategies to mitigate the flood risk to downstream communities. The Corps developed a Long-Term Plan to mitigate for increased flood risk. Features of the 1985 plan included constructing the Sediment Retention Structure, levee improvements on the lower 20 miles of the Cowlitz River and as-needed dredging within the lower Cowlitz River.
The original 1985 Mount St. Helens Long-Term Plan recognized that additional actions would be needed in the future. This Draft Supplemental Environmental Impact Statement is an update of the 1985 Long-Term Plan. To review the original, the Final Mount St. Helens, Washington, Feasibility Report & Environmental Impact Statement, for Toutle, Cowlitz and Columbia rivers, you will find a link in the Documents section below. We encourage individuals, organizations, federal and state agencies to review the draft SEIS and provide comments regarding impacts we may have missed or possible actions not included in the draft SEIS. Comments must be received by Oct. 6, 2014.