Sunset Falls : P-14295

[ Proposed ]

Waterway: South Fork Skykomish

Authorized capacity: 30 mW

License issued: 3/2/2012
License expires:


The proposed hydropower development would consist of the following new facilities:

(1) The Dam: a 7-foot-high, 260-foot-long diversion weir with pneumatically-operated bottom-hinged crest gates;
(2) The Reservoir: a 2-acre impoundment with a normal water surface elevation of 650 feet mean sea level (msl);
(3) The Diversion: an intake structure with three 15-foot-high, 30-foot-wide, 190-footlong tunnels with slide gates and trashracks with 4-inch bar spacing; a 75-foot-high, 120-foot-wide, 200-foot-long cavern structure with three V-shaped fish screens and trashracks with 1-inch bar spacing; a 2,235-foot-long, 19.5-foot-diameter unlined, horseshoe-shaped power tunnel;
(4) The Powerhouse: a 60-foot-wide, 115-foot-long powerhouse containing
two 15-MW vertical Francis turbine generating units for a total installed capacity of 30 MW; a 15-foot-high, 30-foot-wide, 154-foot-long tailrace tunnel;
(5) Transmission Lines: a 75-foot-wide, 100-foot-long switchyard adjacent to the powerhouse; (9) an 8.2-mile-long, 115-kilovolt three-phase overhead transmission line to transmit project power to the regional grid; and
(6) Access Road: an access road leading from an existing road to the cavern structure.

The Skykomish River is part of the Washington State Scenic River system (79A.55 RCW), the legislative purpose of which is to “protect and preserve the natural character of such rivers and fulfill other conservation purposes.” Rivers in the system “shall be preserved in as natural a condition as practical and that overuse of such rivers, which tends to downgrade their natural condition, shall be discouraged.” In addition the section of the Skykomish River that includes Sunset Falls is in a Northwest Power and Conservation Council Protected Area from hydropower development, and has been recommended for designation as a Wild and Scenic River for its Scenic, Recreation, Fish, and Wildlife values by the Forest Service.