After more than 100 years in operation, the century-old diversion dam and power plants located 25 miles east of Seattle needed an upgrade, an effort that included rehabilitating the world’s first underground powerhouse.
The Snoqualmie Falls Hydroelectric Operations are situated on a pristine river above Snoqualmie Falls. In the original design, an underground powerhouse was carved out of bedrock at the base of the falls, complete with a hand-mined 270-ft. shaft for access and the penstock. In 1910, an additional penstock and powerhouse was built, tunneling under a cliff for a flowline that fed external penstocks to a second powerhouse on the riverbank.
More than 100 years later, Barnard contributed to the design for the operation's redevelopment and expansion as PSE began the relicensing process with the Federal Energy Regulatory Commission (FERC). Our work included updating an underground 11.98 MW powerhouse by refurbishing four generators and replacing a fifth, while also enlarging the plant’s cavern and 270-ft.-deep shaft and updating other works. We also constructed a new second powerhouse to house a 12.5 MW turbine generator while preserving the 23 MW turbine generator and updating controls for both units. We completed this project while working around the roughly 2 million tourists who visit the falls and keeping the protection of the environment as an utmost priority.
Location: Snoqualmie, Washington
Owner: Puget Sound Energy
Engineer: Klohn Crippen Berger
Contract Type: Design-Assist; Guaranteed Maximum Price
1,620 LF of new penstocks
New Powerhouse to house 12.5 MW generator
>400 rock bolts