By Jeremy Schwartz
Peninsula Daily News
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Aaron Jenkins with Barnard Construction, the Montana-based firm contracted with the National Park Service on the dam removal, said Friday his crews' goal is to blast about 1,250 cubic yards of concrete from the remnant of Glines Canyon Dam between 1 p.m. and 5 p.m. today.
The time frame is just an estimate, Jenkins cautioned, since high winds or equipment malfunctions could delay the “shot,” as the demolition explosions are called.
The blast, when it happens, will follow a little more than a week of work in which crews drilled holes in the remaining 55 feet of Glines Canyon Dam along the Elwha River to place explosives, Olympic National Park spokeswoman Barb Maynes said Friday.
Down to 35 feet
The roughly 2,000 pounds of explosives are expected to reduce most of the west side of the dam remnant to 35 feet above the riverbed, Maynes said.
The drilling work, begun almost immediately after the last blast Jan. 15, has taken a bit longer than expected because crews have had to deal with steel reinforcement within the concrete in addition to the concrete itself, Maynes explained.
“That [has been] just taking additional time because steel behaves differently than concrete does,” Maynes said.
Maynes said complete dam removal is still expected by this September.
“More drilling, shots, and rubble excavation are scheduled after this shot to fully remove Glines Canyon Dam, hopefully before the next fish window later this [May],” Jenkins said in an email.
The new hole in Glines Canyon Dam is not expected to increase river flows, Maynes said, since there is no more accumulated water behind the dam to come surging through the new opening.
“There's not any extra water that will be released,” Maynes said.
“The river will be flowing over a waterfall that's not quite as high.”
The blast will likely result in more sediment gradually coming down the river as it begins to cut more deeply into the material built up behind the dam, Maynes said.
“It will be carrying more sediment as it cuts further down into the reservoir bed,” she said, adding that it won't be a pulse of sediment as has been seen earlier in the dam-removal process.
“In terms of having impact to the salmon populations, they really aren't in the river at this point,” Maynes added.
Blasting resumed in October after a more than a yearlong hiatus due to river-borne sediment clogging the national park-managed Elwha Water Treatment Plant.
Repairs and improvements to the treatment plant started early last year and completed in October have allowed dam removal to continue, Maynes said.
“And [the plant] is functioning very well,” she said.
The once-210-foot-tall Glines Canyon Dam is being removed via controlled explosions as part of the largest dam-removal project in U.S. history.
Dam removal began in September 2011, and the century-old, 108-foot-tall Elwha Dam was completely gone by March 2012.
The dams were built in the early 1900s without fish passages, barring the Elwha River's legendary salmon populations from reach much of their spawning habitat.
Reporter Jeremy Schwartz can be reached at 360-452-2345, ext. 5074, or at firstname.lastname@example.org.