As 41 percent more sediment than originally believed flows down the newly unleashed Elwha River on Washington’s Olympic Peninsula during the largest river restoration program in U.S. history, teams planted 1,400 pounds of native plant seed in the two former lake reservoirs.
Partially because there’s simply no way of knowing the amount of stored up sediment from damming (with two dams, no less) a river for 100 years and partially because early topography maps misrepresented the elevations in Lake Mills—surveys have the true bottom of the lake 20 feet higher than what reality is proving, meaning there’s 20 vertical feet of extra sediment—crews were surprised to see so much sediment and organic debris pushing past the site of the former Elwha Dam and the now two-thirds removed Glines Canyon Dam.
The influx of mud and debris required emergency fixes to the Elwha Water Facilities plant and has also created logjam and erosion issues in places crews weren’t anticipating. All the changes forced a slow-down in the final stages of the Glines Canyon Dam removal, pushing the next start window into sometime in April. But even with the delay, the project is well ahead of schedule for complete removal by September 2014.
In the meantime, all that exposed former reservoir muck needs life. The revegetation crew was able to get 1,400 pounds of native plant seed—eight species of native grasses and then some wildflower species—put onto the murky wasteland in March, up substantially from the 500 pounds of seed that was sown in the last seeding period, October 2012.
More seeding won’t happen until fall 2013, after Glines Canyon Dam is completely removed.
Another area seeing massive change comes at the mouth of the Elwha, where it flows into the Salish Sea. Not only is the landscape actually changing—a new sand spit is forming—but surveys have shown that kelp amounts have fallen 44 percent from pre-project levels and that the sediment has ripped out much of the seafloor’s vegetation, not altogether a bad turn of events since historic photos show no kelp in the area and the remaking of the seafloor will ultimately turn it back toward its natural state.
One of the most exciting parts of the Elwha project, long after the two fish-killing dams are removed, is the ability to watch the river return to nature, scientists have told me. However that happens.
Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He has also written for TIME, Popular Mechanics, Popular Science and more. You can follow him on Twitter at @tdnewcomb or visit his website here.