Oregon utility Portland General Electric is preparing for the biggest dam removal in Oregon history with the decommissioning of its 21-MW Bull Run hydroelectric project in mid-2007.
Deconstruction of the 47-foot-tall Marmot Dam on the Sandy River is to begin no later than August and last about four months, PGE said. Spokesman Mark Fryburg said the work will be timed to avoid seasonal salmon runs. A second dam, 16-foot-tall Little Sandy Dam, will be decommissioned in 2008.
PGE announced plans in 1999 to decommission Bull Run and Marmot Dam. It signed a dam removal agreement in 2002 with the U.S. Fish &Wildlife Service and the Oregon Department of Fish and Wildlife. The Federal Energy Regulatory Commission approved the plan in 2004.
The utility decided to decommission the 1912-vintage project (No. 477) because the likely cost of environmental protection, mitigation, and enhancement measures associated with relicensing would make continued operation uneconomical. PGE and its ratepayers are to bear the entire $17 million cost for removing the dams, 40 miles east of Portland.
Although the project blocked fish runs on the Little Sandy River since the early 1900s, Fryburg said biologists predict fish eventually will rediscover and repopulate the river once the dams, tunnels, and flumes are gone.
Water is to be sent through the Bull Run powerhouse, draining Roslyn Lake and returning the stream to its natural state, Fryburg said. North of the area, a 9,000-acre area of forests and streams will become property of the Bureau of Land Management. The land was combined with 3,000 acres of purchases by the Western Rivers Conservancy and a 1,500-acre donation by PGE.
PGE will lose 21 MW, lowering its total hydro capacity to 487 MW, Fryburg said. He said there are “no new opportunities for new hydropower generation” in the area, but some of its plants could increase output slightly with upgrades. Since the 1999 decommissioning announcement, PGE has added a 75-MW wind farm and is developing another, 126-MW, wind farm and a 400-MW gas-fired plant.