Solomon Gulch Hydroelectric Project: Final Construction Report for Stabilization of Penstocks

Strategic Insights -

A recent construction project completed by Copper Valley Electric Association has addressed the stabilization of penstocks at the Solomon Gulch Hydroelectric Project in Alaska. The project aimed to provide full embedment, side support, and cover over the conduits, ensuring the structural integrity and safety of the penstocks. The construction report highlights the implementation of a rockery wall to prevent future slope erosion and provide reliable access. Key aspects of the project include excavating a foundation about 18 inches below existing grade, constructing a rockery wall with natural riprap boulders, and placing fill material to ensure stability. The project adhered to specific guidelines for rock placement, including ensuring each rock bears on at least two rocks below it.

Key Takeaways:

  • The project involved the construction of a rockery wall to address slope erosion and provide reliable access to the penstocks.
  • Excavation began 18 inches below existing grade for the base of the rockery wall.
  • Natural riprap boulders were stacked along the exterior of the wall, and super sacks filled with pit run were used to fill voids.
  • All material placed adjacent to the penstock was backfilled with a 1-inch minus material and hand-tamped for proper support and stability.
  • A compacted mixture of 3-inch minus material and pit run was applied above the penstocks.
  • The project followed a remediation concept proposed in Kleinschmidt's September 29, 2023 report, which included construction of a rockery wall, backfilling, and providing a minimum one foot of cover over the penstocks.
  • Photographs taken during the construction are appended to the report for reference.
  • No reservoir drawdown was required for the proposed work, and the penstocks remained in operation during the construction.
  • Local contractors and equipment were used for the work, facilitating the project's completion in four days.

Statistics:

  • Time taken to complete the project: 4 days.
  • Number of photographs appended to the report: several.
  • Number of super sacks used to fill voids: unknown.
  • Amount of 1-inch minus material used for backfilling: unknown.

Sources:

  • Copper Valley Electric Association. (2025). Solomon Gulch Hydroelectric Project: Final Construction Report for Stabilization of Penstocks.
  • Kleinschmidt Associates. (2023). Compliance & Engineering Support – Copper Valley Electric Association, Valdez, Alaska. FERC Dam ID: 2742-AK. Project No. 1863036.02.