Notch by notch, the lowering of the Elwha and Glines Canyon dams allow more of the Elwha River to flow freely, part of the $350 million multi-year process of removing two of the largest dams ever taken out of a river in the United States, in total the largest dam removal project in the nation’s history.

Barnard Construction Co. of Bozeman, Mont., has moved slightly ahead of schedule with the removal, a tedious process that involves the intentional removal of specific amounts of concrete for the sake of downstream habitat and to ensure the properly timed release of sediment that has built up behind the two dams within a few miles of each other in the Olympic National Park in Washington.

blog post photo

Glines crane, courtesy of Olympic National Park

At Glines Canyon Dam, originally built in 1927 at 210 feet tall, crews are again notching away the concrete, lowering the dam and the reservoir level. At certain points in the process, crews place a 14-day hold on the removals, allowing the river to erode back and forth across the newly exposed sediments and naturally sweep away sediment in a controlled manner.

As crews lower the dam, they have also made changes to the equipment used in the process. Recently, underwater pillars—spud piles—were added to the barge holding the equipment used to remove the dam. The spud piles, each 30 feet long, allow the hydraulic hammer to remove the concrete notches that rise above the water, all while the barge rests against the dam itself. At the same time, a smaller hammer-fitted excavator sits on dry land alongside the dam, chipping away at the concrete on one side of the dam.

blog post photo

Glines Canyon, courtesy of Olympic National Park

Work at the Elwha Dam site, built 210 feet tall in 1913, has moved into the water, as crews work to excavate the river’s historic channel. But creating space for the water isn’t the only process ongoing here, as the remaining concrete gravity dam will get yanked out in the next few weeks and more fill material will go away with it. Recently, the river was diverted away from that side of the dam work area, allowing for the easy removal of the gravity dam and for crews to put final grading and rip-rap finishes at the old powerhouse site.

This type of step-by-step work started in fall 2011 and will continue into 2013, allowing the gradual return of natural river flows, vegetation and habitat in a hopeful attempt to restore the last few miles of the Elwha River to its historic state for the first time in over 100 years.

Follow Tim Newcomb on Twitter here