30 NOVEMBER 2024 WorldWide Drilling Resource® A New Intake Gate for Spirit Lake Adapted from Information by U.S. Department of Agriculture Forest Service When Mount St. Helens in Washington, erupted in 1980, an avalanche of sediment formed a natural dam blocking the outlet of Spirit Lake, where it had previously flowed into the North Fork of the Toutle River. If this debris blockage were dislodged by high lake levels in Spirit Lake, the sediment would flow into the Toutle, Cowlitz, and Columbia Rivers, causing loss of life and significant damage. Aging infrastructure and the absence of redundant safety measures for the intake gate itself necessitate the need to replace the existing gate to support safe operations and maintenance of the Spirit Lake infrastructure, downstream communities, and users accessing the area during construction. After 44 years, continued improvements are needed to support operations and maintenance of the Spirit Lake infrastructure that controls the water levels. Work on the multiyear intake gate replacement project and geotechnical drilling project are underway. The goal of the current intake gate replacement project is to improve lake level management, safety, monitoring, and inspection of the tunnel infrastructure. This work is being accomplished by replacing the current single fracture critical steel gate with a double redundant gate system with two flow paths, each through two separate gates. A barge loading facility will be constructed to mobilize equipment over the lake to the existing tunnel inlet, and a coffer dam will be constructed to dewater the existing intake gate structure during construction of the new gate. Geotechnical subsurface drilling is scheduled to begin in 2025. This data will help the Forest Service fully understand the existing conditions of the debris blockage and predict safe operating conditions for the existing infrastructure. Information obtained from the drilling project will also help inform potential alternate systems for managing Spirit Lake water levels. GEOTECH The WWDR Team would like to thank all Veterans, and their families, who have sacrificed so much so we can live free. Veterans Day - November 11, 2024
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