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Latest update on Elwha River dam removal

Post by Jeff Mayor / The News Tribune on March 14, 2012 at 9:23 am with No Comments »
March 14, 2012 9:23 am

Here is an update from Olympic National Park on the work to remove two dams on the Elwha River:

As steady progress continues on dismantling the two Elwha dams, the canyons once blocked by the dams are coming into view.

Elwha Dam

Crews are nearly done removing the concrete gravity dam that filled the river’s original channel, and will soon begin to slowly return the river back to its original channel.

This final diversion will take place over a number of weeks, as contractors carefully control the flow by positioning and repositioning large boulders in the channel. During the diversion process, flows will increase by approximately 150 cubic feet per second as the river lowered 1.5 feet to two feet each day. When the reservoir reaches the 134-foot elevation, a 14-day hold will begin. This is scheduled to begin the week of March 19. The water level in the remaining Lake Aldwell is 49 feet higher than the river bed at the dam site, so the final drawdown will take place over at least a month and will include at least one 14-day hold.

The river within the former Lake Aldwell remains closed to all boating. Significant safety hazards exist, including numerous submerged stumps and boulders in the river, heavy construction equipment, and rapidly changing river conditions. The drained reservoir area at the south end of Lake Aldwell is open to foot travel only. The area north of the ‘gooseneck,’ including the entire construction zone, is closed to all public entry.

Contractors are also restoring the hillside terrain that was excavated during dam construction to support the dam’s penstocks. Seeding of the restored slopes will continue over coming weeks, along with removal of the concrete walls on both the left and right sides of the old dam site.

Glines Canyon Dam

The Glines Canyon Dam has been lowered 12 feet since Feb. 10. Workers reached the 530-foot elevation on March 3 and began a 14-day hold to keep the reservoir level steady for two weeks to allow the river to erode back and forth across the newly exposed sediments.

During the hold period, contractors will begin dismantling the Glines powerhouse and gatehouse and will also chip away at the above-water sections concrete on the dam. Downward notching on the dam will start again after the 14-day hold ends on Saturday.

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