OLYMPIC NATIONAL PARK — A long-planned hold in removing what’s left of Glines Canyon Dam has been extended by at least one month to allow crews to complete modifications to an industrial water-treatment plant that was clogged with mud, leaves and woody debris after heavy rains inundated the Elwha River one month ago.
Meanwhile, Olympic National Park officials said Wednesday that survey errors from nearly a century ago resulted in new sediment estimates of the former reservoir beds of lakes Mills and Aldwell.
Park spokeswoman Barb Maynes said the actual sediment trapped behind the former dams is closer to 34 million cubic yards, rather than the long-estimated 24 million cubic million yards, but that isn’t a factor in the hold.
“Sediment impacts remain . . . well within the parameters of the existing water treatment facilities and other project mitigations,” the park’s project blog said at http://tinyurl.com/9wr5xse.
“Dam removal is still anticipated to be complete well within the contract period.”
A two-month fish window — the latest in a series of predetermined holds on the historic dam-removal project to protect fish — was set to end Jan. 1.
Maynes confirmed Thursday that the hold will be extended through at least Feb. 1 to fix the intake system at the Elwha Water Treatment Plant west of Port Angeles.
The industrial plant, located 2.8 miles from the river mouth, serves the Lower Elwha Klallam tribal fish hatchery, the state Department of Fish and Wildlife fish-rearing channel and the Nippon Paper Industries USA Inc. mill in Port Angeles.
The city’s municipal water supply comes from a well near the river.
The industrial plant is operated by Veolia Water North America, one of several contractors involved in the National Park Service’s $325 million Elwha River restoration project.
Maynes said the modifications are “under way at this point” and are “going well.”
“There will be some work done by an outside contractor as well, but that contract is still being developed,” she said.
Clogging of intake screens led to malfunctions at the industrial plant Dec. 2.
Veolia crews and a team of National Park Service consultants and engineers worked long hours to ensure that the facility continued to produce clean water when flows peaked at about 7,000 cubic feet per second last month.
Flows have since receded to about 1,300 CFS, which is normal for this time of year, and the plant continues to function well, Maynes said.
“Flows are down and turbidity is down, and so the contractor has been able to begin making these modifications,” she said.
A cost estimate for the extra work at the water plant was not available Thursday.
Even with the one-month delay, Maynes said, the dam-removal project should be completed this summer, more than a year ahead of schedule.
“In a sense, a hold on the lowering of the dam is a similar sort of hold we’ve been having for the last couple years,” she added.
The release of sediment has been closely managed and watched by a team of scientists since dam removal began in September 2011.
Dam removal is the centerpiece of the landmark salmon and wildlife restoration project that Congress approved in 1992.
Barnard Construction, the dam-removal contractor, took out the last remnants of the 108-foot-tall Elwha Dam in March 2012.
The once 210-foot Glines Canyon Dam, the tallest dam ever to be removed, has been reduced to a 50-foot waterfall.
Most of the sediment was trapped under Lake Mills, the reservoir behind the upper dam, where tons of sand, silt and cobble already are spilling out.
Park officials said the revised sediment estimate is “not expected to greatly influence either how long or how heavy the river’s sediment loads will be.
“The rate of dam removal, controlled in response to rainfall, floods, spring melt and other factors influences the rate and amount of sediment erosion,” the project blog added.
Reporter Rob Ollikainen can be reached at 360-452-2345, ext. 5072, or at rollikainen@peninsuladailynews.com.
