Large Dam Removals for Restoration of the Elwha River

Elwha and Glines Canyon Dams are located on the Elwha River in northwestern Washington State, on the Olympic Peninsula. Elwha Dam was completed in 1913 at river mile (RM) 4.9, and includes a 108-foot-high concrete gravity section, gated spillways on both abutments, and a powerhouse with four generating units rated at a combined capacity of 14.8 megawatts (MW). Glines Canyon Dam was completed in 1927 at RM 13.4, and includes a 210-foot-high concrete thin arch section, a gated spillway on the left abutment, a thrust block on the right abutment, and a powerhouse with a single generating unit rated at 13.3 MW. Both dams are currently owned by the federal government and are operated and maintained for the National Park Service by the Bureau of Reclamation. Glines Canyon Dam is located within Olympic National Park. Elwha Dam impounds Lake Aldwell, which has a surface area of 267 acres and a storage capacity of 8,100 acre-feet at elevation 197.0. Glines Canyon Dam impounds Lake Mills, which has a surface area of 415 acres and a storage capacity of 40,500 acre-feet at elevation 590.3. Both dams are operated for hydropower generation under run-of-the-river conditions, and contain a total estimated volume of over 20 million cubic yards of sediment. Each dam has a “high hazard” classification based on the potential for loss of life in the event of failure, and has been modified by others to improve performance for flood and earthquake loads. The removal of Elwha and Glines Canyon Dams has been authorized and funded by Congress to provide anadromous fish passage to more than 70 miles of the Elwha River and its tributaries, and for full restoration of the Elwha River ecosystem. Reclamation has completed final designs and specifications for the removal of both dams, for contract award later this year. The demolition work must accommodate river flows during dam removal, and facilitate sediment management through controlled releases and systematic construction schedules, while achieving all project objectives including environmental compliance. The paper highlights project developments from the Elwha Act through contract award. 15 pp, 8 references.