How was the Elwha dam removed?
In 1992, Congress passed the Elwha River Ecosystem and Fisheries Restoration Act, authorizing dam removal to restore the altered ecosystem and the native anadromous fisheries therein. After two decades of planning, the largest dam removal in U.S. history began on September 17, 2011.
How do they take down a dam?
The structure of the dam is carefully removed to minimize downstream impacts. The contractor usually starts at the far side of the dam and removes stone and concrete by working back towards his river access point.
When the Elwha dam was removed did the fish come back?
Fish were anticipated to return to the upper reaches of the Elwha as soon as a year after dam removal was complete. While the river might never return to historically large runs, after 15–20 years or more, there should be a recovery of salmon runs to some sort of “pre-dam” condition.
How did they remove the Elwha Dam from Lake Aldwell?
The first step in removing the Elwha dam was to lower the reservoir’s water level by approximately 15 feet using the existing water intakes and spillway. This process began on June 1, 2011 following the closure of the powerhouse. A temporary diversion channel was then excavated through the left spillway to allow Lake Aldwell to be further drained.
What happens when water recedes from Lake Aldwell?
As the water receded from Lake Aldwell, the Elwha River returned to its historic channels, sediment was washed away and an ancient forest floor was revealed, along with pieces of our history.
How did they remove the dam at Lake Mills?
First, water levels in the Lake Mills reservoir were lowered to the bottom of the spillway gates. Using barge-mounted hydraulic hammers, the first 17 feet of the dam were removed down to the waterline. The next 173 feet of the dam were removed using a notching process.
Why was the Lake Aldwell dam so important?
The treatment plants primarily protected water users from sediments that had accumulated in the Lake Mills and Lake Aldwell reservoirs for decades following dam construction. The facilities continue to take in surface water for treatment and provide clean water for municipal, industrial and hatchery needs.