EDITOR’S NOTE — See video animation of how the two dams will be demolished — http://tinyurl.com/elwhavideo.
Watch on your home computer (via six webcams) as both dams are torn down — http://tinyurl.com/damwebcams.
PORT ANGELES — The booms of explosions that motorists on state Highway 112 may hear during October and during January through February will be music to the ears of those awaiting the return of salmon to the upper reaches of Elwha River.
Eight to 10 as-yet-unscheduled blasts will carve a river diversion channel into rock next to the 11-story Elwha Dam five miles upstream from the mouth of the Strait of Juan de Fuca, said project manager Brian Krohmer of Barnard Construction Co., the Boseman, Mont.-based contractor overseeing the dams’ demolition.
Krohmer said no studies have been conducted to determine how far the sound of explosions and giant hammers will travel from the site, about seven miles west of downtown Port Angeles.
Holes for the first blast will be dug about Oct. 3 or Oct. 4.
They will be detonated two to four days after that, Krohmer said.
The second drilling and blasting will occur immediately following that first one, with no blasting at all during November and December to protect migrating salmon.
Monday hammering
On Monday, an excavator equipped with a large hydraulic hammer will begin to chisel its way into the concrete at the top of the 108-foot Elwha Dam, a “gravity dam” with a great deal more mass than the Glines Canyon Dam, which is an “arch dam.”
The first blast at the Elwha Dam will be in early October, Krohmer said.
The Elwha Dam’s powerhouse — dormant since June 1 when the dams stopped producing an average 19 megawats megawatt-hours of electricity annually, enough electricity to power 1,700 homes — will be demolished beginning in November.
At Glines, in a process that will be mirrored at the Elwha Dam except when explosives are used, excavator-mounted hammers have already begun to pound away, notching the massive walls down piece by piece.
The first chips were taken off the 210-foot-tall Glines Canyon Dam — 21 stories tall 13 miles upstream from the Strait — last Thursday.
Twenty-eight cubic yards of concrete was removed that day.
Between 60 and 100 cubic yards of material is expected to be removed a day at the height of production, Krohmer said.
The combined 37,500 cubic yards of detritus from both dams — 3,500 dump-truck and dump-truck-trailer loads — will be transported to two county gravel pits off Harrick Road near U.S. Highway 101 and Place Road of Highway 112.
Both are west of Port Angeles and so will avoid city traffic, Clallam County Engineer Ross Tyler said Tuesday.
“We made sure there was room for these volumes in each location,” Tyler said.
Debris destinations
Glines debris is going to the Harrick Road pit and Elwha Dam debris to the Ranger pit.
“I’ve been told by the contractor they have specific work windows they have to do this work,” Tyler said.
“It’s going to be scattered or sporadic,” he said of the dump-truck traffic.
“I don’t believe there’s going to be any noticeable impact to traffic at all.”
The Glines dam is expected to be lowered to the water line, about 18 feet, within two weeks, Krohmer said.
Then, large notches will be made into the structure to allow the reservoir to be drained another 12 feet before demolition continues.
Barnard’s $27 million contract with the National Park Service allows up to three years to complete demolition so the river freely flows once again, but the dams will be completely down before then, Krohmer predicted.
“Yes, it should be prior to September 2014,” he said.
Aaron Jenkins, project superintendent, and Krohmer said their biggest challenge is the weather.
If the river swells, “we will get our people out and let it run its course,” Krohmer said.
Won’t release schedule
Bozeman, Mont.-based Barnard will not discuss a schedule of what specifically happens when during demolition, and neither the company nor Olympic National Park, within whose boundaries the Glines Canyon Dam falls, would release the contract.
Barnard and the park said the information is proprietary.
“We have 1,095 calendar days to complete the project, starting on Sept. 15, 2011,” Barnard said in an email.
“There are many unknowns that could occur, potentially extending our schedule goals significantly.”
Barnard also must abide by a schedule geared toward the species that dam removal will revive: the Elwha River’s storied salmon runs.
The company will not be allowed to draw water down from Lake Aldwell, created by the Elwha Dam, and Lake Mills, created by the Glines Canyon Dam, for almost half of the entire three-year term of the contract.
That’s because the project schedule must be shaped around “fish windows” during November, December, May, June, August and the first half of September of each year to protect the river’s migrating fish stocks, said Brian Winter, Olympic National Park’s Elwha restoration project manager.
Drawing down water from the lakes increases the sediment flow, which could hurt chances for salmon restoration, he said.
An estimated 24.5 million cubic yards of the stuff is piled underwater behind both dams.
“The idea behind the fish windows is that the river will clean up to natural conditions, which we know fish will do under natural sediment [conditions],” Winter said.
“We want to ensure they return to the Elwha River.”
Barnard won’t be sitting completely silent during that time, though.
Floodgates and powerhouses at the two dams will be demolished, concrete and steel debris hauled, and equipment maintained and repaired, Krohmer said.
The National Park Service is the lead agency for the $325 million Elwha River Restoration Project, intended to restore 11 species of anadromous fish — those that migrate upriver from the seat to spawn — to once-plentiful numbers.
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Senior Staff Reporter Paul Gottlieb can be reached at 360-417-3536 or at paul.gottlieb@peninsuladailynews.com.
