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Snohomish PUD designs low-cost, low-impact hydro project

From the April 17, 2014 issue of Public Power Daily

Originally published April 17, 2014

After a series of studies and design analysis, Snohomish County Public Utility District has developed an innovative plan for a proposed hydropower project that requires no dam, weir, or river barriers. That will reduce construction costs by $10 million, the Washington State utility said. The Sunset Fish Passage & Energy Project could power up to 22,500 homes at maximum output, Snohomish said.  

"We have proven success delivering low-impact hydropower projects that provide multiple benefits to our customers," said Kim Moore, PUD assistant general manager of Water, Generation & Corporate Services. "This project could be a valuable addition to our portfolio. Among the low-impact projects we identified in the past seven years, it’s the lowest cost power source."

As part of the project the PUD would make improvements to an aging, 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.

Snohomish’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, the PUD said. In addition, more efficient turbines at a proposed powerhouse would increase annual energy production.

The no-dam design is possible due to the unique geography of the South Fork Skykomish River, the utility 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 project’s powerhouse, Snohomish said. Sufficient water would remain in the river for fish, aesthetics, and recreation.

In addition to the Sunset Project, the PUD is assessing two other local hydro power projects above Snoqualmie Falls near North Bend. These projects are the lowest cost renewable energy sources available locally, better in price than wind, solar, tidal, and biomass/biogas, Snohomish said.


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