OLYMPIC NATIONAL PARK — Demolition of the two dams on the Elwha River will resume earlier than expected — today rather than after Jan. 1.
That’s because a period mandating a halt in work to protect fish migration, which is called a “fish window,” ended two weeks early.
Barnard Construction crews began in September chipping away at the two dams, built without fish ladders nearly a century ago, as part of a $325 million federal project to restore the river’s once-famous salmon runs.
They had to quit dam removal work temporarily Nov. 1, the concern being that any further lowering of the two dams’ reservoirs would harm fish through the release of sediment.
That hiatus was expected to last until the first of next year.
But an interagency team of biologists monitoring the return of fish to the Elwha River determined that the late fall runs of chum salmon had trickled to an end, Barb Maynes, Olympic National Park spokeswoman, said last week.
Divert channel
So today, Barnard Construction crews will begin diverting the river channel around the Elwha Dam and start preparations for resumption of dam removal at Glines Canyon Dam, said Brian Krohmer, project manager.
“It will be a gradual process,” Krohmer said.
The river now flows through a channel blasted from concrete on its west side, where a spillway once stood.
The channel will be moved to its original course on the east side around the remnants of the Elwha Dam, which was lowered from 108 feet to 60 feet before the fish window began.
Diversion may be finished today or as late as Tuesday, Krohmer said.
A drawdown of the remains of the reservoir behind the dam, the former Lake Aldwell, will follow, with flow increased by about 150 cubic feet per second, Maynes said.
More of the dam will be taken down at the end of the week, Krohmer said.
Glines Canyon Dam
Glines Canyon Dam demolition is scheduled to resume Dec. 27.
This week, crews will reassemble a barge and excavator-mounted hydraulic hammer at that dam, which was taken down from 210 feet to 178 feet before the fish window began.
There are three fish windows annually.
The windows, which last about two months at a time, prevent work that will stir up sediment for five to six months of the year.
During the fish window, adult chum salmon were collected and transferred to the Lower Elwha Klallam tribe’s fish hatchery.
That hatchery is serving as a clear-water refuge during the dam removal period, when extensive sediment is being released into the river, Maynes said.
Offspring of the collected chum will be released into the river this spring.
Work done so far
While work taking down the dams was on hold, Barnard Construction crews have demolished most of the Elwha Dam powerhouse and removed some nine miles of power lines from the two dams, which once provided electrical power for the developing cities of Port Angeles, Port Townsend and Poulsbo, as well as the Navy yard in Bremerton.
The 120-foot-tall surge tower at the Elwha Dam came down Thursday.
Demolition of the Elwha Dam is expected to be finished in early 2013, with the Glines Canyon Dam — at originally 210 feet tall, the tallest ever removed in the nation — completely down a year later.
The Elwha Dam was built in 1913 five miles from the mouth of the river, and the Glines Canyon Dam, which formed Lake Mills 14 miles upriver, followed in 1927.
Access to the demolition sites is not allowed.
To watch the process, images from six webcams are available at www.nps.gov/olym or http://tinyurl.com/3srf3vx.
Removal work at the Elwha Dam also can be seen from the overlook trail, accessed from a gate just south of the Elwha RV Park on Lower Dam Road off state Highway 112.
There is no access to a vantage point for the Glines Canyon Dam right now.
The park is working to provide public viewing opportunities for the Glines Canyon Dam by next summer, Maynes said.
