Thursday, March 22, 2012

Environmental Restoration

A marvelous environmental restoration project for the Olympic Peninsula is well underway. The Elwha dam, 100 years old, has been removed. Glines Canyon Dam will be gone within the year. An article by Lynda V. Mapes in the Seattle Times, giving a progress report on the project, is fascinating. Here's a little bit of it:
Built beginning in 1910, the Elwha Dam sat five miles from the river's mouth. Contractors in September started taking it down, as well as Glines Canyon Dam, 8 miles more upriver.

The $325 million taxpayer-funded project is intended to restore the salmon runs and ecological productivity of the Elwha and its watershed.

Once home to all five species of Pacific salmon, the river is regarded as one of the best opportunities for environmental restoration anywhere. More than 83 percent of the Elwha watershed is pristine, and permanently protected within Olympic National Park.

On March 9, at about 5 p.m., contractors removed the last of the dam from the river. On Friday, they let the river back into its natural bed, from a man-made diversion channel where it had been routed to allow workers to demolish the dam in the dry.

During dam removal, contractors moved the river back and forth between the diversion channel and its bed 10 times in all.
It fairly boggles the mind, thinking of human beings moving such a river back and forth, again and again. Turns out, the Elwha dam was "ready to topple":
Brian Krohmer, project manager on the job for Barnard Construction, said crews were lucky on the weather — and they also encountered a dam quite ready to topple.

"How do I say this without insulting the people that made it?" said Krohmer, whose office in the construction trailer is decorated with the tattered American flag that flew over Elwha Dam. "Let's just say it wouldn't have passed safety standards today."

A trip to the river Monday revealed a transformed landscape. The river races past where it used to choke at the dam. The former Lake Aldwell is a vast delta of sediment.

The river has been cutting through the sediment, creating badlands and hoodoos of sculpted, terraced fine material. The river, milky with sediment, rushes cold and fast through soft cliffs that calve into the water.

The cliff sides are gray and wrinkled as elephant skin where the dropping water levels have rippled and nudged the fine material into ridges. Or they are smooth, where entire hunks have fallen away at once.

On the flats, tiny prints of raccoon show animals already are exploring the new landscape. It's easy walking, soft as a sandy beach.

Along the river, a ghost forest offers a hint of the grandeur that was: gigantic cedar stumps, wider than a king-size bed, stud the sediment flats. They are all that remain of the 1,000-year-old trees that were logged before the gates of the dam were shut and the forest turned into a lake.

Up at Glines Canyon Dam, the drama of demolition is still unfolding.

On Monday, an operator worked a giant excavator fitted with a steel chisel bit, ramming the concrete face of the dam, chipping it down chunk by chunk. By now, contractors have chewed the dam down about 64 feet; they're about a third of the way finished.

Water poured over the broken face of Glines Canyon Dam, falling in a fury of white water into the canyon below, and throwing a double rainbow of spray. The operator worked his rig — a trackhoe excavator — from a barge bouncing on the surface of what's left of Lake Mills.

Big slugs of sediment stuck behind the dams have yet to start really hitting the river. But as excavation goes deeper, that material will start to move downstream.
Mapes takes notes of objects found in the soft mud of the newly exposed canyon-- a large wooden wagon wheel,ceramic blue insulators, and so on. The ceramic blue insulators, like the dam itself, was the leading edge of modernity one hundred years ago. Its destruction now, in another new century, signifies the hope that we can recover some of what was sacrificed to achieve that modernity.

Interestingly, the University of Washington's Friday Harbor Labs has an apprenticeship focused on the sedimentary impacts that will follow the dams' removal. "Students work with UW Oceanographers to examine the impacts on the coastal and marine ecosystems from removing two dams from the Elwha River, the biggest watershed on the Olympic Peninsula. The dams are scheduled to be removed during 2011 with the goal of habitat restoration. However, we do not yet understand the full range of effects that “restoration” will have. Apprentices explore the effects of the added sediment discharge in high quantities during dam removal near the mouths of rivers."  Now this is my idea of exciting science!

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