out the dam-removal project on the Elwha River — already the
biggest anywhere in the world — is even larger than
In the project, long predicted to affect more than 24
million cubic yards of sediment, the amount of sediment once
impounded by the dams is actually about 34 million cubic
yards, said Barb Maynes, spokeswoman for the National Park
The park service is in charge of the $325 million project,
which began in September 2011.
The new estimate is partly the result of discovering a
long-standing error in mapping Lake Mills, with elevations
recorded 20 feet higher than they really were back in 1917,
Those incorrect measures were passed along in a 1976 map
used by engineers in their sediment estimates for the dam
removal project, because the 1976 map had been marked as
corrected — when it wasn't.
The error eventually was detected when it became clear the
elevations recorded on the two maps were the same. Further,
as scientists walked the landscape in surveys since dam
removal started, the emerging landscape wasn't matching the
"The mistake has finally been located and corrected," Maynes
Scientists have long understood that management of the
immense amount of sediment stuck behind the dams would be
the trickiest part of the project, driving everything from
the pace of dam removal to mitigation needed to accommodate
The revised sediment estimates are still within the
capacities of mitigation projects built to manage sediment
released by the dam removal project, Maynes said, from
higher levees to water-treatment plants.
But there already have been surprises, and there are likely
to be more, as the unprecedented project takes its course.
Dam removal has been put on hold for at least a month,
beginning in January, as contractors work to modify an
industrial water treatment plant built as part of the dam
removal project to protect the quality of water used in a
new tribal hatchery, a state salmon rearing channel, and
water used by a Port Angeles paper plant.
Intake screens at the plant became clogged with leaves and
sticks transported by the river after winter storms, leading
to a cascade of malfunctions, including settling tanks that
had to be repeatedly cleaned out, Maynes said.
None of the malfunctions was serious enough to harm the
facilities the water-treatment plant protects, or to disrupt
their function, Maynes said, although they had to operate
with less than the promised quality of water the plant is
supposed to deliver.
Work on the plant has meant shutting down removal of Glines
Canyon Dam for a month, to avoid disturbing more sediment
until the plant is back in satisfactory shape, Maynes said.
She did not have an estimate on the cost of the work, or
know who would pay for it.
Elwha Dam was built in 1910 in the lower river without fish
passage, and was removed last March. Glines Canyon Dam,
built about eight miles upriver, is about two-thirds gone.
Contractors should be able to stay on schedule even with the
delay this month and get that dam out by summer, Maynes
The dam-removal project had no peer in terms of the amount
of sediment that scientists are managing as the dams come
down — even before the estimate got bigger.
At 210 feet tall, Glines Canyon Dam also is the tallest dam
Already the project has opened about 25 miles of spawning
habitat for fish. Pinks, chinook, steelhead and coho have
all been spotted utilizing every portion of the new habitat,
from side channels to the main stem.
Biologists counted 203 redds dug above the former Elwha Dam
site after more than 500 adult chinook surged into upriver
with the removal of Elwha Dam. And while scientists saw
salmon carcasses along the river last year, this year they
are only seeing pieces.
Animals are eating the fish coming back to the river, from
otters to bears to water ouzels, in the beginning of a
broader, ecosystem recovery, said John McMillan, a biologist
frequently surveying the river for NOAA fisheries.
The survival of thousands of new plantings in the emerging
landscape of the former lake beds has also been much better
than predicted, with only about 8 percent of the plants
dying off in the first year, despite a very dry summer, said
Joshua Chenoweth, who is helping to lead the replanting
Sediment the plants are growing in retained moisture from
the former lakes well into September, Chenoweth said, giving
new plants a good start.
Lynda V. Mapes: 206-464-2736
On Twitter @lyndavmapes.