The U.S. Army Corps of Engineers is seeking comments on a draft Environmental Assessment addressing the impacts associated with a proposal to raise the spillway crest elevation of the Sediment Retention Structure, located near Mount St. Helens in Cowlitz County, Wash.
The purpose of the proposed SRS Spillway Raise Project is to increase sediment storage capacity behind the existing SRS, at River Mile 13.2 of the North Fork Toutle River. The SRS is a single-purpose structure completed in 1989 to trap and control downstream movement of volcanic sediments eroding from the debris avalanche on Mount St. Helens.
The sediment storage capacity of the SRS will be increased by constructing a roller-compacted-concrete structure on the existing spillway, thereby raising the overall spillway crest elevation by up to 10 feet.
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Dredging Today Staff, March 1, 2012; Image: usace