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Blue Lake Dam, Sitka, AK

Project data

Location: Sitka, Alaska, United States

The Blue Lake Dam Expansion project is located in Sitka, Alaska and is an expansion of the hydroelectric dam which provides the power for Sitka. The main scope includes a new intake, penstock, gate tunnel and gate house and the addition of approximately 90 ft onto the existing arch dam. The expansion of the dam will provide approximately 27 % more electricity for Sitka and in turn will create more opportunity for growth while maintaining energy independence. 


  • Single sided tieless climbing solution
  • Shoring and support brackets at large heights
  • Engineering and design support


Barnard Construction

Customer's benefit

  • PERI is providing continuous engineering and site support to Barnard Construction to ensure a safe working environment and to make sure all system benefits are fully utilized.
  • Excellent logistics support delivering to remote site in Alaska
  • Custom solutions using standard PERI parts
Shawn Perrin

The formwork provided by PERI for the dam, especially for the cantilevered spillway, was critical to the success of this remote project.  Customer support and logistics were top notch in delivering formwork via a 5 day trip by barge.

PERI solution

  • The massive arch of the dam is being formed using a combination of VARIO GT 24, CB and PERI’s new single sided climbing system, SCS, which allows the loads from the fresh concrete pressure to be transferred without ties through the brackets into the climbing anchors of the previous concreting section. 
  • VARIOKIT was used for the soffit shoring under the spillway, while SB brace frames, overlooking the dam at spectacular heights, were inverted to provide support for the spillway concrete. 
  • PERI RUNDFLEX was utilized to form a vertical gate shaft tunnel and a gatehouse was formed using TRIO.