Bull Run Hydroelectric Project

The Bull Run Hydroelectric Project was a Portland General Electric (PGE) development in the Sandy River basin in the U.S. state of Oregon. Originally built between 1908 and 1912 near the town of Bull Run, it supplied hydroelectric power for the Portland area for nearly a century, until it was removed in 2007 and 2008. The project used a system of canals, tunnels, wood box flumes and diversion dams to feed a remote storage reservoir and power house. The entire project was removed because of rising environmental costs. Marmot Dam on the Sandy River was demolished in 2007,^[1] and the Little Sandy Dam on the Little Sandy River was taken down in 2008.

History and overview

Wood box flume, after nearly 100 years of service, passing over the emptied Little Sandy riverbed. Rail tracks are mounted on the top of the flume for a maintenance trolley (note the dog at the footings for scale).

The Mount Hood Company began the project in 1906, building the Little Sandy Dam to divert water through a 3-mile (4.8 km) long wood box flume to Roslyn Lake. The last few miles of the Little Sandy River were effectively eliminated since the entire river was diverted, and all salmon and steelhead habitat above the dam was lost. Roslyn Lake, completed in 1911, was built on a plateau, about 320 feet (98 m) above the Bull Run River and Powerhouse. The 160-acre (650,000 m²) lake acted as a forebay for the powerhouse and was used by the community for recreation. The powerhouse was completed and put into operation in 1912,^[2] the same year that the Mount Hood Company was bought by Portland Railway Light and Power Company, which would later become Portland General Electric.^{[citation needed]}

In 1913 a second dam was built on the (Big) Sandy River. The 47 ft (14 m) high Marmot Dam supplied the majority of the project's water, about 600 ft³/s (17 m³/s), but used only a fraction of the Sandy's normal flow. The Sandy River, however, is on the other side of the Devil's Backbone ridge from the Little Sandy River. A series of canals and tunnels were required to reach the Little Sandy Dam, where their flows were combined and diverted to the flume and Roslyn Lake.

The Marmot Dam has always had fish ladders to allow migration of Salmon and Steelhead, however they performed poorly at first and required frequent upgrades and maintenance, which continued into the 1990s. Fish screens were added in 1951 to prevent downstream migrating fish from entering the diversion and being killed by the water turbines.

In 1989 the original timber crib Marmot Dam was replaced with a concrete structure.

Operations

Marmot Dam. The fish ladder is visible on the far side of the dam.

Penstock intake at Lake Roslyn

The powerhouse had a nameplate generating capacity of 21 MW and produced an average 13 MW, or about $6,600,000 worth of electricity annually (at local customer rates).^{[citation needed]}

Facts

Decommissioning

Time lapse video of Dam removal.

The decommissioning project required significant oversight, because Marmot Dam was the largest concrete dam ever removed in the United States.^[3] PGE sought and received initial approval for the project from the Federal Energy Regulatory Commission in 1999. PGE later employed RESOLVE, a non-profit dispute resolution organization, to help develop a detailed consensus plan among the interested parties. An agreement was reached in 2002 on the decommissioning.^[4] The primary issues addressed by the reviews were the impact on fish species (particularly salmonids), their habitat, and the effect of the release of 1 million cubic yards (750,000 cubic meters) of sediment on the river course.^[5][6][7] In 2004, PGE allowed its operating license to lapse, and filed a notice stating: "[...]the likely cost of providing the necessary level of protection, mitigation, and enhancement for the resources affected by the Project would outweigh the economic benefit of generation at the Project over the life of a new license[...]"^[4] The project continued to operate with license extensions while decommissioning awaited approval. In 2006, PGE requested special approval of the decommissioning from the National Marine Fisheries Service, because of the project's potential impact on coho salmon. The final review was conducted by the United States Army Corps of Engineers, which granted approval for the decommissioning on May 21, 2007. A spokesman for the Corps stated that the removal project was unusual, because "Large dams usually don't get removed."^[5]

Before Marmot Dam could be removed, a temporary coffer dam had to be built upstream. When this phase of the project was complete, the removal of the permanent concrete dam could proceed. The destruction of the permanent dam began on 26 July 2007, when a public controlled demolition weakened the structure. The rest of the dam was destroyed using pneumatic hammers over approximately 4 months.^[8] The last concrete from Marmot Dam was removed on September 30, 2007,^[9] and the final phase of removal was completed on 20 October 2007, when the temporary earthen dam washed away and the Sandy River began to flow freely for the first time since 1912.^[10]

PGE removed Little Sandy Dam in 2008, eliminating Roslyn Lake. This restored Little Sandy River flow and made salmon and steelhead migration once again possible.^[11] In May 2009, a fish biologist reported that salmon and steelhead were spawning upstream of the former dam.^[12] PGE donated 1,500 acres (6.1 km²) of the dam site to the Western Rivers Conservancy.^[11] This land is planned to form the core of a 9,000-acre (36 km²) natural refuge and public recreation area, which will be managed by the Bureau of Land Management.^[11] PGE's water rights on the river were to transfer to the state.^[13] As of 2009, PGE biologists continue to monitor the streams.^[11]

References

External links

• Settlement Agreement Concerning the Removal of the Bull Run Hydroelectric Project..., PGE and interested parties, October 24, 2002. ( 1.2MB pdf)
• Numerical Modeling of Sediment Transport in the Sandy River, OR Following Removal of Marmot Dam, Technical Report prepared for PGE by Stillwater Sciences, March 2000. ( 3.7MB pdf)
• Evaluation of Geomorphic Effects of Removal of Marmot and Little Sandy Dams and Potential Impacts on Anadromous Salmonids, Technical Report prepared for PGE by Stillwater Sciences, March 2000. ( 2.1MB pdf)
• Clean Water Act § 401 Certification Evaluation and Finding Report For the Decommissioning of the Bull Run Hydroelectric Project (FERC No. 477), Sandy River Basin, Clackamas County, Oregon 1.2MB pdf.
• McOmie, Grant (2005-04-11). "Marmot Dam Comes Down Soon". KATU News. http://web.archive.org/web/20050416121835/http://www.katu.com/outdoor/story.asp?ID=76402. 
• Restoring the Sandy River overview of the project from American Rivers
• Marmot Dam removal from the Sandy River MarmotDam.com
• Taylor, William Thomas; Daniel Harvey Braymer (1917). American Hydroelectric Practice. McGraw-Hill Book Company. pp. 123–124. http://books.google.com/books?id=vBYhAAAAMAAJ.