PORT ANGELES, Wash. — The Elwha River drains out from Olympic National Park, a pristine place in the world. And as recently as a year ago, the river looked the part: it babbled its final miles in water clear enough to see the bottom. Now it runs thick with grainy sediment the color of chocolate milk.

But believe it or not, that is a good thing, or at least the roundabout result of one.

The first of two dams built on the river in the early part of the 20th century was torn down in March, and the second, larger one, farther upstream, is now partly demolished. The dams all but killed the river as a wild place once renowned for its bounty of fish, especially the salmon that spawned in tributaries deep inside what became, in 1938, a national park.

But with the river’s restoration — or redemption, as some fervent supporters of the $325 million project put it — has come a mind-bogglingly large surge of sediment. More than 24 million cubic yards of silt, sand, clay and rock — enough to fill the area of a football field to a depth of 2.2 miles, according to the United States Geological Survey — accumulated behind the dams, much of it the detritus of glaciers.