Starting today, the National Park Service will begin the largest dam removal project in U.S. history as part of a sweeping effort to restore the Elwha River that runs through Washington's Olympic National Park.

The Elwha and Glines Canyon hydroelectric dams, built in 1913 and 1927, respectively, supplied electricity for nearly a century to thousands of Pacific Northwest residents. But the dams also severed Pacific salmon migration routes that were once among the country's most robust.

Prior to the construction of the two dams, the Park Service estimates that 400,000 salmon migrated annually up the 45-mile river linking the Olympic Mountains to the Juan de Fuca Strait. The river currently supports only about 3,000 chinook and chum salmon.

But NPS contractors today will begin using diamond-wire cutters to carve out 7.5-foot sections of the Glines Canyon Dam, slowly draining the Lake Mills reservoir behind it.

Then on Monday, workers will begin constructing a cofferdam upstream of the Elwha Dam to divert water from Lake Aldwell into channels that will dry the reservoir and allow for the destruction of the concrete dam, said Dave Reynolds, a spokesman at Olympic National Park.

The $27 million dam removal effort, 20 years in the making, will take about three years to complete, Reynolds said.

"It's going to be a long process," he said. "I see the start of dam removal as a huge milestone, but I like to think of it as a new beginning for the river. I think it's in keeping with the goals of the NPS to preserve the natural environment and to protect and restore natural processes."

Ecosystem-scale benefits

Indeed, removing the dams and returning the Elwha River to a free-flowing state is the centerpiece of a $325 million effort to restore the entire ecosystem by allowing the chinook and chum salmon to swim as far as 70 miles up the river and its tributaries within the park.

As part of the effort, the U.S. Geological Survey is implementing a large-scale research and monitoring project to measure the ecological conditions before, during and after dam removal in an effort to determine the impact of the dams on the salmon.

"This is one of the biggest and most significant river restoration efforts the world has ever seen," said Bob Irvin, the president of American Rivers, a national conservation group that supports dam removal projects as a means of restoring river ecosystems. "We will witness a river coming back to life, with great benefits for people and the environment."

David Graves, northwest program manager for the National Parks Conservation Association in Seattle, said the return of the salmon will attract scores of animals to Olympic National Park that feed on the fish, including golden eagles.

"The ecological benefits of the project are incredible," Graves said. "It will be fascinating to see how quickly the ecosystem can restore itself in terms of the salmon returning and the benefits of this to the ecosystem in the park. For the past 100 years, [the river] has lost the benefits of the salmon and the nutrition they provide to over 130 species of plants and animals."

Abundance of caution

The project comes with risks, however. By virtue of being the largest dam removal project in the country's history, there is no blueprint for how to do it safely. Nor is there certainty that all possible scenarios have been evaluated and harm to wildlife and people adequately mitigated.

The Park Service has conducted a detailed environmental analysis of the possible impacts of the dam removals on Olympic National Park and the surrounding area. The agency also has completed 43 pre-dam removal projects, including shutting down the hydroelectric power-generation system that the dams supported, Reynolds said.

Among the possible outcomes NPS officials said they are closely monitoring are a surge in sediment flow downstream once the dams are breeched, potentially destroying wildlife, polluting drinking water and exacerbating downstream flooding.

An estimated 18 million cubic yards of sediment -- equivalent to more than 1 million dump truck loads -- have built up behind the walls of the two dams, and simply removing them would create strong water currents that stir up the sediment and cloud the water -- lowering water temperatures and ultimately killing fish downstream (Land Letter, March 31).

The Park Service last spring completed work on a massive salmon hatchery designed to protect native fish from being buried in silt when the dams are removed. In addition, NPS this summer captured and removed large numbers of federally threatened bull trout from the river and transported them to two locations north of the dams to avoid being harmed by increased sediment flow, Reynolds said.

In an effort to protect its drinking water supply, the downstream city of Port Angeles, Wash., built two water treatment facilities last year that will take water from Elwha River, filter it, and then send the clean water to the city's residents.

Levee improvements

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.

"I'm pretty confident, and I don't think they would be going ahead with the dam removals if they didn't think they'd done enough" to guard against flooding, said Brenda Francis, a spokeswoman for the Lower Elwha Klallam Tribe.

Tribal members have lived in the region for centuries and depend on the salmon for subsistence. And 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 decades ago.

So to the Lower Elwha Klallam Tribe, the risks are worth it, Francis said.

"The tribe has always felt it's our job to take care of our earth, and when the dams were up, we felt we weren't doing our job and the tribe has tried for years to remove the dams," she said. "So we're very excited. Everyone's ecstatic about it."

Streater writes from Colorado Springs, Colo.

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