The Marmot dam demolition on the Sandy river will be the largest dam removal in the Pacific Northwest in 40 years and the largest ever in the US state of Oregon. It is the first phase in PGE's US$17M Bull Run hydroelectric project decommissioning plan, developed in consensus with 23 diverse organisations, including environmental groups, state and federal natural resource agencies, local governments and businesses. The plan also provides for the removal of Little Sandy dam on its namesake river next summer, followed by the removal of most other project components. The removal has been approved by the Federal Energy Regulatory Commission (FERC).
The Sandy river is home to winter steelhead, spring Chinook and coho salmon, all listed as threatened under the federal Endangered Species Act. The State of Oregon lists coho as an endangered species. Removal of the dam will give the fish access to about 160km of stream habitat above the dam.
Following the detonation of explosives, which cracked the concrete face of the dam on 24 July, heavy equipment began taking apart the structure. Demolition of the dam should take about two months. The concrete chunks will be recycled for road surfacing. During this work, the river will bypasses the dam, diverted by earthen cofferdams which will be washed away in late autumn by natural stream flows.
Other components of the work include:
* The 1433m tunnel, which takes Sandy river water from Marmot Dam through a ridge and then into the Little Sandy River, will be closed this year.
* Roslyn Lake will be drained and the land restored to natural contours in 2008.
* An approximately 5km long wooden flume running out of the Little Sandy dam to the lake will be demolished in 2008.
* Unless a new owner is found, PGE will remove the project's power house in 2009.
PGE, headquartered in Portland, will donate 607ha of its Sandy River Basin land to the Western Rivers Conservancy, which will convey most of the property to the US Bureau of Land Management for permanent protection. The land will form the foundation of a planned 3642ha conservation and recreation area. The Sandy will remain one of the top Chinook salmon and steelhead fishing destinations in Oregon, while Marmot dam removal will enhance whitewater rafting and kayaking on the river.
PGE is surrendering its rights to the water 'in stream', meaning no one can remove that amount of water in the future.
PGE announced that it would remove the Bull Run Hydroelectric Project in 1999 after the company determined that demolition would be more economical for its customers than maintaining the facility and upgrading it to modern fish protection standards. PGE however said it remains committed to hydro power and is in the process of upgrading fish protection at its remaining hydro projects.
Next summer's demolition of the 4.9m high Little Sandy dam will allow fish passage at that location for the first time in almost a century. The structure currently diverts almost all of the water out of the lower Little Sandy River for power production. More than 16km of habitat will be restored when the natural flows are restored to the Little Sandy river.
Located about 64km east of Portland, Marmot dam was built in 1913 to power a trolley that carried city dwellers out to the countryside and was rebuilt in 1989 after a flood. At 22MW, Bull Run is one of PGE's smallest generating facilities, and its power has already been replaced with wind power and other sources.
