The National Park Service is preparing to undertake the largest dam removal project in U.S. history as part of a broader effort to restore the Elwha River in Olympic National Park.
NPS has targeted Sept. 17 to begin tearing down the Elwha and Glines Canyon dams that for nearly a century have severed salmon migration routes in the river.
Before the Elwha and Glines Canyon dams were built in 1913 and 1927, respectively, an estimated 400,000 salmon migrated annually up the 45-mile river linking the Olympic Mountains to the Juan de Fuca Strait.
Today, officials estimate the river supports only about 3,000 chinook and chum salmon, said Barb Maynes, a spokeswoman with Olympic National Park.
The $27 million dam removals, which will take as long as three years to complete, are the centerpiece of a larger $325 million effort to restore the river, which is the largest watershed in Olympic National Park.
Once the dams are gone, the Elwha River will return to its free-flowing state, allowing the chinook and chum salmon to swim as far as 70 miles upriver and its tributaries within the park.
That, in turn, will restore the entire ecosystem, as the return of the salmon will attract scores of animals that feed on the fish, including golden eagles and bears.
"The way to think of it is in terms of the pounds of fish that will be returning into the system," said Pat Crain, a fisheries biologist at Olympic National Park. "When you consider a pink salmon weighs 4 pounds when it returns from the sea, and even if we have just 100,000 in the river, that's 400,000 pounds of food that's there for wildlife, or for nutrient-loading for riparian plants, or for benthic insects. Each year, you'll infuse this large quantity of biomass into a system that's essentially been lacking that for nearly 100 years."
To the Lower Elwha Klallam Tribe, the river restoration is long overdue.
Tribe members have lived in the region for centuries and depend on the salmon for subsistence. Restoring the river to its natural free-flowing state will also allow the tribe access to sacred sites that were flooded when the river was dammed.
Brenda Francis, a tribe spokeswoman, said older members remember when the river was full of salmon. Francis has an old photograph in her office of a tribal member holding a salmon nearly 6 feet long.
"We were always told to take care of our earth and take care of our surroundings," Francis said. "Since the dams have been put up, the environment has been damaged because the fish have not been able to pass through. It has put a hole in our ecosystem."
But removing the dams is a complicated process. Because the dams have stood for decades, an estimated 18 million cubic yards of sediment -- equivalent to more than 1 million dump truck loads -- have built up behind the structures. If the dams are not properly managed, water currents can stir up the sediment, which in turn clouds the water, lowers water temperatures and ultimately can kill fish downstream.
The sudden release of billions of gallons of sediment-laden water could also affect drinking water for the city of Port Angeles, Wash., downstream of the dams.
To protect the city's drinking water, NPS paid to build two water treatment facilities that will take water from Elwha River, filter it, and then send the clean water to the city. That project was completed last year.
Flood protection is also a concern because sediment flows that result from removing the dams could raise the riverbed by more than 2 feet in some places. To address this problem, the Park Service is raising and extending a federal levee at the mouth of the Elwha River that provides flood protection to the Lower Elwha Klallam Tribe on the river's east side and a dike that protects private properties on the west side.
The Park Service is also nearing completion of a massive salmon hatchery designed to protect native fish from being buried in silt when the dams are removed and the current carries the sediment downstream.
"A lot of time and money has been spent by various universities and agencies to study what this will mean to the river and the park," said David Graves, the northwest program manager for the National Parks Conservation Association in Seattle. "And we've been very impressed by the amount of scientific research that has gone into this project and the mitigation."
Most of those mitigation projects are being funded with a portion of $750 million allocated to NPS under the American Recovery and Reinvestment Act signed into law by President Obama in 2009.
A total of $54.7 million has been allocated for the dam removal mitigation projects -- making it the largest single Park Service project funded with the ARRA money.
"This is a huge project and it has been under development for a long time," said Maynes, the NPS spokeswoman. "But we are really proud of it."
Streater writes from Colorado Springs, Colo.