Hydroelectric Decommissioning
Until October 2007, the river was dammed and the flow rate regulated. The Bull Run Hydroelectric Project diverted water from the Sandy River at the Marmot Dam to the Little Sandy River at the Little Sandy Dam. Water was diverted from the Little Sandy River to Roslyn Lake through a wood box flume. The artificial lake supplied the 22-megawatt Bull Run hydroelectric powerhouse and emptied into the Bull Run River.
On July 24, 2007, Marmot Dam was demolished by engineers using 650 pounds (290 kg) of explosives. It was followed by the Little Sandy Dam in 2008, and Roslyn Lake ceased to exist. The decommissioning restored the Little Sandy River to steelhead and salmon runs for the first time in a hundred years. Marmot Dam had always contained a fish ladder. Portland General Electric, the dams' owner, donated 1,500 acres (6.1 km2) of land near the dams to a nature reserve. The final phase of the Marmot Dam removal was completed on October 19, 2007, when the temporary dam was demolished and the river started to flow freely for the first time since 1912.
Read more about this topic: Sandy River (Oregon)