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Blue Lake Dam, United States of America

The heightening of the dam at Blue Lake ensures the self-sufficient energy supply of the inhabitants of Sitka, Alaska, USA.
The VARIO formwork for the vertical edge areas was climbed on CB Platforms.
Difficult site accessibility and a complex geometry presented the construction team with major challenges.
The formwork concept was based on the CB and SCS Climbing Systems and was perfectly complemented by the use of VARIOKIT system components.

Project data

Location: Sitka, United States

  • 25 m dam heightening
  • 2.44 m thick, rounded reinforced concrete wall with a 35 m radius
  • Over a length of about 40 m, the dam is built like a spillway structure with a downstream cantilevered dam crest of 6.34 m.

The increase in height and expansion of the existing dam for the Blue Lake reservoir by 25 m increases the efficiency of the hydroelectric power station by 27 % to 15 MW. The new arch dam now has a 70 m overall height with the dam crest more than 80 m long. In addition, new intake structures and penstocks for power plant operations were realized.

Requirements

  • Difficult access 
  • Complex, challenging building geometry
  • Transfer of high loads resulting from the enormous cantilever in the area of the dam crest 

Customer

Barnard Construction, Bozeman

Customer's benefit

  • Excellent project support and logistics despite the remote location of the jobsite
  • A formwork solution that was exactly catered to the construction sequence of the challenging building structure
  • Extremely flexible brackets to adapt to the complex geometry
Portrait of Shawn Perrin, Site Manager,  Barnard Construction, Bozeman
Shawn Perrin
Site Manager

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

  • VARIO formwork for vertical edge areas climbs upwards on CB platforms.
  • The SCS climbing system is combined with SB brace frames and MULTIPROP shoring towers for the spillway section with the enormous cantilever. The transfer of the extraordinarily high loads is done with connectable SB brace frames, which are used horizontally.
  • For the edge areas, which are to be built vertically, the CB climbing system and the VARIO GT 24 girder wall formwork are used.
  • Climbing formwork units of the SCS system ensure load transfer during single-sided shuttering, and here the brackets can be adjusted to the complex geometry in an extremely flexible way.
  • The formwork concept, which is based on the CB and SCS climbing systems, is usefully supplemented by VARIOKIT system components.