Snohomish County Public Utility District No. 1 in the US says it has developed a highly innovative plan for a proposed hydropower project southeast of Index that requires no dam, weir or river barriers, reducing construction costs by $10 million.
The no-dam design is possible due to the unique geography of the South Fork Skykomish River, the PUD said. Upstream from Sunset Falls, the river turns sharply - a complete 180 degrees - creating a deep pool of water, which can accommodate an underwater intake structure. The water for the project would flow from the upstream intake to an underground tunnel through solid bedrock a half-mile to the PUD powerhouse. Sufficient water would remain in the river for fish, aesthetics and recreation.
As part of the project the PUD would make improvements to an ageing, state-owned trap-and-haul facility that trucks salmon upstream above three impassible waterfalls to 90 miles of spawning habitat. The utility also is studying potential road and recreation improvements.
The PUD's updated design modifies the water intake area and fish screens to cut excavation needs in half. It also reduces construction time by an estimated six months. In addition, more efficient turbines at a proposed powerhouse would increase annual energy production.
In addition to the Sunset Project, the PUD is assessing two other local hydropower projects above Snoqualmie Falls near North Bend.
Photo: The no-dam design is possible due to the unique geography of the South Fork Skykomish River. (Source: Snohomish County PUD)
