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United States. Federal Energy Regulatory Commission

Rock Island Hydroelectric Project: Spillway Downstream Parapet Wall Replacement Project

Strategic Insights

— 2 min read

The Public Utility District No. 1 of Chelan County, Washington has submitted an update to the Federal Energy Regulatory Commission regarding the Rock Island Hydroelectric Project, specifically the Spillway Downstream Parapet Wall Replacement Project for Bays 1-3. This update follows the authorization of construction for Bays 10-14 in December 2024 and subsequent authorizations for Bays 4-31 in March 2025. The project aims to replace the existing spillway downstream parapet wall and resolve conditions reported in April 2024.

Key Takeaways:

  • The Federal Energy Regulatory Commission authorized construction of the Spillway Downstream Parapet Wall Replacement Project, Bays 10-14 on December 3, 2024.
  • The construction of Spillway Downstream Parapet Wall Replacement Project, Bays 4-31 were authorized on March 4, 2025.
  • The updated construction documents for the Spillway Downstream Parapet Wall Replacement Project at the Rock Island Hydro Electric 1 Project for Bays 1-32 include Bays 1, 2, and 3.
  • The proposed design for the downstream parapet replacement in Bays 1 to 3 differs from the other spillway bays due to the decreased radius of the spillway and changes in loading during crane travel.
  • The new beam transfers all crane loads directly into the underlying spillway piers and has no rigid connection to the existing roadway deck, limiting future Alkali-Aggregate Reactivity (AAR) related concrete growth concerns.
  • The District requests the Board of Consultants' response to the question of whether the project does not interfere with ongoing AAR growth and should be allowed to proceed as a means to restore spillway operation by June 30, 2025.
  • The District will make any requested revisions to the enclosed documents and then submit the final package with the BOC response to the FERC and request authorization to proceed with this additional phase of construction work.
  • The enclosed material meets the Critical Energy Infrastructure Information (CEII) requirements under 18 CFR 388.113c.

Statistics:

  • The project has been authorized for Bays 1-32, with Bays 1, 2, and 3 included in the updated construction package.
  • The new beam will transfer all crane loads directly into the underlying spillway piers.
  • The project has been designed to limit future Alkali-Aggregate Reactivity (AAR) related concrete growth concerns.

Sources:

  • Douglas Johnson, P.E., FERC to Martha Whiteman, Chelan PUD, Project No. 943, Accession No. 20241203-3052 (Dec. 3, 2024).
  • Douglas Johnson, P.E., FERC to Martha Whiteman, Chelan PUD, Project No. 943, Accession No. 20250304-3084 (Mar. 4, 2025).
  • Douglas Johnson, P.E., FERC to Martha Whiteman, Chelan PUD, Project No. 943, Accession No. 20250319-3058 (Mar. 19, 2025).
  • William Christman, P.E., Chelan PUD to Douglas Johnson, FERC, Project No. 943, Accession No. 20240415-5299 (Apr. 15, 2024).

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