Prelude to removal - Elwha River dams

On February 29,2000, the United States purchased Elwha and Glines Canyon Dams on the Elwha River from private owners for the purpose of removing the dams to restore anadromous fish runs within the basin. This paper presents an overview of the history of the dams, including the October 1912 foundation failure of Elwha Dam and subsequent repair, events leading up to the purchase by the Federal Government, the engineering plans for removal, sedimentation issues, and status of the project.

Historically, salmon runs on the Elwha River on the north coast of the Olympic Peninsula in Washington provided the chief economic and cultural basis for the Lower Elwha Klallam Indian Tribe. Construction of the dams by private interests for hydropower blocked salmon access to the basin. Those runs were partially replaced by fish hatcheries. With the passage by Congress of the Elwha River Ecosystem and Fisheries Restoration Act in 1992 (P.L. 102-495), the restoration of the Elwha River ecosystem and reestablishment of the native anadromous fisheries were authorized.

The 108-foot high concrete gravity Elwha Dam was constructed between 1911 and 1913 approximately 5 miles upstream from the mouth of the Elwha River on the Strait of Juan de Fuca. Shortly after initial filling in 1912, a foundation blowout occurred under the gravity dam section, draining the 8,100 ac-ft reservoir in a matter of hours. Repairs to reestablish the dam occurred over the period 1913-1919. The powerplant was completed in 1917. It is estimated that 4 million cubic yards of sediment has been collected in Lake Aldwell upstream of the dam.

Glines Canyon Dam is located approximately 8.5 miles upstream from Elwha Dam within Olympic National Park. Glines Canyon Dam is a concrete arch structure 210 feet high with a crest length of 150 feet. The dam and powerplant were completed in 1927. The dam impounds Lake Mills with a storage capacity of 40,500 acre-feet. It is estimated that over 14 million cubic yards of sediment has been trapped in Lake Mills.

A 1996 Environmental Impact Statement identified the removal of the dams to restore native fish runs as the preferred alternative which is now the intended course of action. Upon transfer to the Federal government in February 2000, the Bureau of Reclamation began operating the dams and powerplants, and providing oversight for dam safety during the interim period. Currently, the National Park Service and Reclamation are jointly working to implement downstream infrastructure modifications required prior to removal of the dams. 11 pp.