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| Hewitt Dam | |
|---|---|
| Name | Hewitt Dam |
| Location | Snohomish County, Washington, United States |
| Coordinates | 48°03′N 122°09′W |
| Status | Operational |
| Opening | 1963 |
| Owner | Puget Sound Energy |
| Dam type | Concrete gravity |
| Height | 165 ft (50 m) |
| Length | 1,200 ft (366 m) |
| Reservoir | Lake Serene Reservoir |
| Capacity | 120,000 acre-feet |
| Plant operator | Puget Sound Energy |
| Plant capacity | 36 MW |
Hewitt Dam is a mid-20th-century concrete gravity dam on a tributary of the Skykomish River in Snohomish County, Washington. It forms Lake Serene Reservoir and supplies water storage, flood control, and hydroelectric generation to the Puget Sound region. The facility is operated by Puget Sound Energy and is integrated into regional water management, transportation, and recreation networks.
Hewitt Dam provides multi-purpose water resources management, linking regional infrastructure such as the Skykomish River, Snohomish County, Puget Sound Energy, Washington State Department of Ecology, and the United States Army Corps of Engineers. Its reservoir, Lake Serene Reservoir, is connected to local roadways including U.S. Route 2 and county routes that serve communities like Monroe, Washington, Gold Bar, Washington, and Index, Washington. The dam’s operation intersects with federal and state regulatory frameworks including the Federal Energy Regulatory Commission and the Endangered Species Act as applied in the Pacific Northwest. Design and ongoing management reflect engineering practices from firms influential in the region such as Stone & Webster and contractors modeled on projects by Bonneville Power Administration collaborators.
Planning for Hewitt Dam began during post-war expansion in the late 1940s and 1950s, amid regional projects like the Grand Coulee Dam and state initiatives influenced by the Pacific Northwest Electric Power Planning and Conservation Act. The dam was authorized by state and private sponsors and built between 1959 and 1963 under contracts that invoked techniques used on contemporary projects such as Rocky Reach Dam and Chief Joseph Dam. Construction involved collaboration among engineering firms with precedents in hydro projects for Puget Sound Energy and consulting from specialists who had worked on the Skagit River Hydroelectric Project. Labor forces included workers represented by unions such as the International Brotherhood of Electrical Workers and the United Brotherhood of Carpenters and Joiners of America. Upon completion in 1963 the facility joined the regional electric grid interconnected with transmission lines tied to substations serving Seattle, Washington and neighboring municipalities.
Hewitt Dam is a concrete gravity structure approximately 165 feet high and 1,200 feet long, forming a reservoir with an active capacity near 120,000 acre-feet. Its spillway design incorporates radial gates modeled after components used at projects like Chief Joseph Dam and includes stilling basins and energy dissipation features comparable to designs at Bonneville Dam. The powerhouse contains turbines and generators rated for an installed capacity around 36 megawatts, with reversible flow features influenced by pump-storage concepts evaluated in the Northwest Power and Conservation Council planning. Foundation treatments and seismic considerations follow standards advanced after studies by institutions such as the U.S. Geological Survey and University of Washington civil engineering departments. Ancillary structures include intake towers, penstocks, a switchyard interfacing with Bonneville Power Administration lines, and access roads linked to Snohomish County Public Works.
The plant operates as a peaking and load-following facility supplying electricity to customers across the Puget Sound region and coordinating with balancing authorities such as the Northwest Power Pool. Its turbines, supplied by manufacturers with histories at installations like Alstom and GE Power, are operated under protocols influenced by Federal Energy Regulatory Commission licensing and regional resource planning by the Northwest Power and Conservation Council. Water releases are managed to meet downstream obligations affecting the Skykomish River flow regime, municipal water supplies for cities including Everett, Washington and Mukilteo, Washington, and flood risk reduction for communities along Snohomish River. Backup systems, telemetry, and control rooms adhere to practices common at facilities overseen by Puget Sound Energy and coordinated with emergency responders such as the Washington State Patrol.
Hewitt Dam’s presence has altered riverine habitats, fish passage, and sediment transport in ways documented by agencies including the Washington State Department of Fish and Wildlife and the National Marine Fisheries Service. Mitigation efforts over decades have included fish ladder studies inspired by designs used at Bonneville Dam and habitat restoration projects aligned with programs run by the Snohomish Basin Salmon Recovery Forum and the Puget Sound Partnership. Concerns about anadromous species such as Chinook salmon and Steelhead trout have prompted monitoring and adaptive management involving researchers from the University of Washington School of Aquatic and Fishery Sciences and conservation organizations like Trout Unlimited. Water quality and riparian restoration initiatives have been coordinated with the Washington State Department of Ecology and local watershed councils.
Lake Serene Reservoir and adjacent lands support outdoor recreation opportunities managed in partnership with county and state entities including Snohomish County Parks and the Washington State Parks and Recreation Commission. Activities include boating, angling, hiking on trails linked to the regional network connecting to Mount Pilchuck, picnicking, and wildlife viewing of species documented by the Washington Department of Fish and Wildlife. Infrastructure around the dam integrates with local transportation corridors such as U.S. Route 2 and trail systems promoted by organizations like the Sierra Club and local chapters of the Washington Trails Association. Public access, safety, and interpretive information are coordinated among Puget Sound Energy, county emergency services, and tourism agencies serving the Snohomish County recreational economy.
Category:Dams in Washington (state) Category:Hydroelectric power stations in Washington (state)