OLYMPIC NATIONAL PARK — The remaining 60 feet of Glines Canyon Dam will linger until at least July because of sediment clogging a water treatment plant on the Elwha River.
Demolition of the dam, originally set to resume two months ago after a fish window closed, won’t restart until after repairs are completed on Elwha Water Treatment Plant intakes, the National Park Service announced this week.
Construction crews with Lakewood-based Macnak Construction are completing $1.4 million worth of what National Park Service officials are calling “corrections” to the Elwha Water Treatment Plant, one of three water facilities built as part of the $325 million Elwha dam removal and restoration project, Olympic National Park spokeswoman Barb Maynes said Wednesday.
The three facilities are the Elwha Surface Water Intake Structure, the Elwha Water Treatment Plant and the Port Angeles Water Treatment Plant.
Macnak crews could be seen replacing fish screens on the intake structure Wednesday.
The repair work is expected to wrap up in mid-April, Maynes said, but Glines Canyon Dam removal won’t restart until July so treatment plant staff can assess the corrective work and make sure it is doing its job.
“We just want to make sure we have an understanding of the things that need to be corrected before we begin releasing sediment in large quantities again [through further dam removal],” Maynes said.
Contractor Barnard Construction has been ahead of schedule in removing the dams, with the demolition of Elwha Dam finished a year ago.
Maynes said treatment plant staff also is trying to determine why the plant is not handling the sediment loads as expected.
“We’re eager to finish dam removal, but our priority right now is to get to the bottom of these issues,” Maynes said.
The project is still expected to be complete before September 2014, she said.
The problems started last fall, when sediment and woody debris began clogging up the intakes, Maynes said.
The plant still is taking in water and sending it to the plant’s downstream customers, which comprise the Port Angeles Water Treatment Plant — designed to treat drinking water for the city — plus Nippon Paper Industries USA, the state Department of Fish and Wildlife’s fish-rearing channel and the Lower Elwha Klallam tribe’s fish hatchery, Maynes said.
The Elwha Treatment Plant, however, has not been able to supply as much filtered water as planned, and plant staff have had to work around the clock to clear the intake’s screens so water can get to the plant, Maynes said.
The amount of sediment released since dam removal started in September 2011 has followed scientific models produced before the removal began, Maynes said, though the sediment is interacting with treatment plant intakes in an unexpected way.
“We know the sediment is entering the water intake in a way that was not intended.” Maynes said.
When asked for more detail, Maynes said: “No, I can’t expand on that. I don’t really know if anyone knows the answer to that just yet.”
Maynes said one challenge to completing the construction work and analyzing why the plant is having trouble with the sediment is doing it all while the plant is up and running.
“We’re not shutting it down to look at it; we’re doing all this analysis while it’s still operating,” Maynes said.
Scientists watching the Elwha River flow freely after being locked behind the Elwha and Glines Canyon dams for nearly a century estimate that 6 million cubic yards of sediment — of a total 34 million — already has moved down the river.
The National Park Service upped the estimate of total sediment thought to be trapped behind the dams from 24 million cubic yards to 34 million after a century-old surveying error was found.
Reporter Jeremy Schwartz can be reached at 360-452-2345, ext. 5074, or at jschwartz@peninsuladailynews.com.
