Dave's Creek Substation Flood Mitigation

Authors: Grundhauser, Kacy, HDR; Lowe, Cynthia, HDR

Video Presentation

Abstract

The Dave's Creek Substation is located on the Kenai Peninsula near the community of Sunrise and on the banks of Quartz Creek. Channel migrations in 2021 brought floodwaters close to the substation threatening its operation. Approximately 300 feet upstream from the substation, Quartz Creek shifted main channel flow to a remnant side channel and caused flooding that created an unacceptable level of risk to the electrical substation, adjacent transmission line and the Sterling Highway. In spring 2022, breakup revealed that Quartz Creek shifted most of its flow into the remnant channel greatly reducing main channel flow. Immediate action was taken to place flexible intermediate bulk containers (Super Sacks) to temporarily divert most of the flow back into the main channel. Two primary alternatives were evaluated to permanently protect the substation and redirect water back into the main channel: a steel sheet pile wall and a riprap guide bank. The use of riprap to create a guide bank, frontage embankment and buried trench to protect two sides of the substation and main transmission lines were selected for design and construction. Project stakeholders consisting of the Cooper Landing Advisory Planning Commission, Kenai Peninsula Borough Planning Commission, Alaska Department of Fish and Game, Alaska Department of Natural Resources, Kenai River Center, and the Army Corps of Engineers issued necessary approvals and permits for project construction. Construction began in late September 2022.The design was adjusted throughout the project to accommodate agency requests, the further migration of Quartz Creek into the side channel, and the development of sinkholes. Final quantities placed were 242 cy of filter rock and 1,430.32 cy of riprap Class III. The project was completed in late October 2022 and considered a success to the project stakeholders, who expressed their satisfaction during the final walkthrough.

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