Glines Canyon Dam

Glines Canyon Dam was built on the Elwha River in 1927 to generate electricity for the growing communities and industries of the Olympic Peninsula. The concrete structure stood about 210 feet high in a narrow canyon and created Lake Mills, a long reservoir upstream from Elwha Dam. Its hydroelectric plant operated as part of a two-dam system that produced relatively modest power by regional standards, but the facilities provided a local energy supply for much of the twentieth century.

The project was privately developed by the Olympic Power and Development Company. Neither dam included effective fish passage, so the lower river remained accessible to migratory fish while the upper watershed was cut off. The resulting loss of access affected salmon and other anadromous species, while the reservoirs trapped sediment that would otherwise have moved toward the river mouth and coastal habitats.

Glines Canyon Dam became a restoration priority because its benefits were outweighed by ecological damage and because its operating license was difficult to renew under modern environmental standards. The federal government acquired the dams and surrounding lands, and Congress authorized removal through the Elwha Ecosystem and Fisheries Restoration Act in 1992.¹ The legislation made restoration of the river’s fisheries and ecosystem the central objective rather than continued hydropower production.

The site was incorporated into Olympic National Park, whose protected status helped preserve the watershed while the project was planned. Engineers had to address sediment stored behind both dams, water-quality risks, worker safety, and the logistics of dismantling a large concrete structure in a remote canyon. These constraints made the project more than a conventional demolition.

Removal of Glines Canyon Dam took place from 2011 through 2014, following the removal of Elwha Dam downstream. Crews lowered the structure in stages by drilling, blasting, and excavating concrete, allowing the reservoir to drain while monitoring turbidity, slope stability, and downstream conditions. The final section was removed in September 2014, completing the dismantling of both dams.

Once the barriers disappeared, the Elwha River could carry water, wood, gravel, and fine sediment through its former reservoir sites. Scientists documented rapid physical changes, including the formation of new channels and deposition of sediment downstream.² Revegetation and habitat work followed, while fish began recolonizing reaches that had been inaccessible for roughly a century. Recovery was expected to unfold over decades rather than in a single season.

One of the project’s less visible consequences was the release of sediment, not simply the return of flowing water. Lake Mills had stored millions of cubic yards of material, and its exposure transformed a reservoir floor into a changing landscape of bars, wetlands, and pioneering vegetation.² The sediment pulse also temporarily increased turbidity and altered beaches and estuarine habitat near the river’s mouth.

The dam’s removal had cultural significance as well as ecological importance for the Lower Elwha Klallam Tribe, whose treaty-protected fisheries and relationship with the river had been harmed by the dams. The Elwha project also became a reference case for large-dam removal: it demonstrated that obsolete hydropower infrastructure can be dismantled while monitoring complex geomorphic and biological effects, rather than treating restoration as a purely mechanical task.

Lake Mills

The reservoir formed behind Glines Canyon Dam on the upper Elwha River.

Anadromous fish

Fish that migrate from the ocean into freshwater to reproduce, including Pacific salmon.

Sediment pulse

A short-term downstream movement of accumulated sand, gravel, silt, and other river material after a barrier is removed.

Elwha Ecosystem and Fisheries Restoration Act

The 1992 federal law that authorized acquisition and removal of the Elwha River dams and restoration of the river ecosystem.