Y--Mt. St. Helens Sediment Retention Structure, Spillway Elevation Project

The Mt. St. Helens Sediment Retention Structure Spillway Elevation Project, managed by the Department of Defense through the Endist Portland office, involves raising the spillway crest elevation of an existing structure on the North Fork Toutle River in Cowlitz County, Washington. Originally built in the late 1980s to manage sediment from the Mt. St. Helens debris avalanche, the facility requires modifications to increase the pool elevation behind the structure. Access to the site is provided via a combination of gravel access roads, the embankment dam, the concrete outlet works, and a paved roadway on the spillway approach pier. The scope of work encompasses mobilization and demobilization, the implementation of water diversion measures to allow for dry construction, and extensive rock excavation to create a low flow channel and plunge pool. Additionally, the contractor is responsible for rock foundation preparation using dental concrete and the construction of a roller-compacted concrete structure upstream of the current spillway crest. This project is categorized under NAICS code 237990 and was processed under solicitation number W9127N-12-R-0010.