To produce more hydropower, the city of Sitka, Alaska, added a 15.9-megawatt powerhouse to the 1950s-era Blue Lake Dam.

Design firm Hatch Consultants worked to bring the 145-ft-tall concrete arch dam to its maximum geotechnical height by raising it 83 ft.

Getting water to the turbines required building a new intake tunnel and concrete intake structure. That involved 120 vertical ft of rock excavation on the shores of Blue Lake.

The $92.45-million project’s remote location on Baranof Island created logistical challenges for the project team. All key materials, including concrete, arrived via weekly barge shipments. The dam’s location in a canyon allowed vehicle access from only one side. The team relied on three cranes to get the work done.

Blue Lake Expansion Project

Sitka, Alaska

Key Players
City and Borough of Sitka, Alaska
Lead Design Firm Hatch Associates Consultants
General Contractor Barnard Construction Co.
Structural Engineering Hatch Associates Consultants
Mechanical and Plumbing Engineering Hatch Associates Consultants
Civil Engineering Hatch Associates Consultants