Lessons of the Elwha River: Managing Health Hazards During Dam Removal

Abstract

On the northwest edge of the continental United States, in some of the quietest and most rain-drenched lands in all of North America,1 runs the glacier-blue Elwha River. It arises from the Elwha Snowfinger, a perennial snowfield in Washington’s Olympic National Park, and flows 45 miles northward through basalt canyons and old-growth forest before spilling into the Strait of Juan de Fuca. The river traverses the reservation of the Lower Elwha Klallam Tribe, a people who have relied on the river’s salmon for physical, spiritual, and cultural sustenance for millennia.2 The river’s two hydroelectric dams have become stars of a four-decade-long saga, culminating in the complete removal of the lower Elwha Dam this past summer, with the taller Glines Canyon Dam breached but not yet gone; it should be fully removed by summer 2013. Together they make up the biggest dam-removal project and the second biggest restoration project ever undertaken by the National Park Service (NPS), after the Everglades.3 With the lower Elwha Dam gone, the Elwha River ecosystem—as well as the local tribal community—has begun a dramatic transformation. Deconstruction of the Glines Canyon Dam should finish in summer 2013. Tearing down dams restores ecosystems in the long term, but in the short term it releases mass quantities of pent-up sediment and, in some cases, contaminants. As Chinook salmon and ... This summer Chinook and other salmon species spawned in tributaries that had been blocked for a century. Meanwhile, more than 24 million yd3 of clay, silt, sand, gravel, and cobble that had built up behind the dams began to flow.4 This sediment, especially the gravel, is necessary for the restoration of fish spawning habitat, and downstream beaches and stream beds long starved of gravel, sand, and silt will ultimately be bolstered by its return. But in the short term, excess turbidity remains the biggest concern for the watershed’s human and animal residents during the next 3–10 years.5,6 Dramatic increases in turbidity are expected to kill fish and diminish spawning success7 as well as affect water for drinking, hatcheries, and a paper mill. Negotiating how to mitigate these concerns took decades—and a lot of money. Tearing down dams releases mass quantities of pent-up sediment and, in some cases, contaminants in the short term, but it restores ecosystems in the long term. As the fish begin returning to the Elwha River, the biggest dam removal in history is being touted as a model for future dam breaches.