OLYMPIC NATIONAL PARK — Lake Mills, now 18 feet lower than usual, is a bit murkier than it was a few weeks ago, but that’s just a sign that a channel dug at its south end is doing its job, according to Olympic National Park.
The channel, finished about a month ago, was made to erode the delta located at the point where the Elwha River flows into the man-made lake.
“You can see that it’s doing its job,” said park spokesman Dave Reynolds.
“It’s incising into the delta and taking care of the coarse sediment.”
The Bureau of Reclamation, which operates the Glines Canyon dam, assisted in that process by lowering the lake 18 feet from Oct. 20 to Oct. 29.
That exposed additional sediment that needs to be eroded by the river as part of the $350 million project to remove the dam and its sister downstream, the Elwha dam, National Park Service said.
The actual tearing down of the dams is expected to begin in September and end in March 2014.
The sediment, 13 million cubic yards in all, has been accumulating behind the Glines Canyon dam since it was built in 1927.
The Park Service said the sediment improves fish habitat and needs to be dispersed throughout the rest of the river.
Reynolds acknowledged that some of the sediment from the delta is going to settle back into the lake bed and not make its way past the dam.
“About a third of the sediment will wash all the way to the [Strait of Juan de Fuca],” he said.
“Generally, about 50 percent of the sediment will remain in the reservoirs, whether Mills or Aldwell,” Reynolds added.
“Now, the rest of that, some of it will accumulate in the river downstream.
“The fine sediment will wash rather quickly directly to the Strait.”
Reynolds said the trout that inhabit the lake haven’t been affected by the murky conditions.
The lake will be closed to boaters until fall rains refill the reservoir, he said.
Reynolds said the Park Service is going to let the river erode a small delta at Lake Aldwell on its own.
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Reporter Tom Callis can be reached at 360-417-3532 or at tom.callis@peninsuladailynews.com.