We’ve Inherited a Dam Problem

Morning had shifted to afternoon. Sun rays beamed through clouds and lit up evergreen slopes. A class of college students stood on top of Alder Dam in Washington State. A few feet to our left, a quiescent lake sprawled as far as the eye could see. A few feet to our right, past a chain-link fence and concrete barrier, white water plummeted 330 feet down into a narrow rocky gorge. Sparrows rode thermals wafting out of the valley. The professor described the dam’s history and uncertain future. His parents’ generation built dams like this one, his generation reaped the benefits, and now our generation must tear them down.

Alder Dam was constructed in 1945 as a concrete arch rising 330 feet above the river canyon below. Image from http://eatonvilletorainier.com/2014/01/alder-dam-1945/ (CC BY-NC-SA 3.0)

Debates about dams have raged for the last two centuries (Billington et al., 2005). Opponents point to stories of catastrophe. Dams have almost completely cut off all routes in Maine for fish that leave the ocean to spawn in freshwater lakes and streams (Hall et al., 2010). Almost 200,000 people had to emergency evacuate when California’s Oroville dam, the tallest dam in North America, was damaged in 2017 (Vahedifard et al., 2017).

Still, many concrete behemoths proved their worth. During the economic crisis in the 1930s, when unemployment had risen to 25%, President Roosevelt authorized the construction of Bonneville Dam in part to create jobs (Billington et al., 2005). The Hoover dam stores enough water to irrigate two million acres and generates enough hydropower to serve 1.3 million people every year (NPS). These marvels of engineering inspire pride, awe, and curiosity.

There are nearly 100,000 dams in the United States (ASCE, 2017). While agencies, organizations, and bystanders have been arguing over the pros and cons of building dams, the dams themselves have ignored the quarrel and grown old and decrepit. Their average expected lifetime? 56 years. The cost to repair and maintain them? Nearly $45 billion (ASCE, 2017).

The United States Geological Survey classifies major dams in the United States on their hazard risk, taking the potential for human death into account (USGS, 2016). As of 2016, over 15,000 dams had high-hazard potential (ASCE, 2017).

Why can’t dams function forever with just a few minor repairs? One reason is sediment buildup. Rivers don’t just carry water. They also carry everything that happens to get washed into that water. Mud, sand, twigs, pollutants, an occasional lone flip flop, all course down a river until they get stuck behind a dam. Water pools to form a calm reservoir. Everything else sinks to the bottom. Over hundreds of years, all that sinking stuff builds up.

While standing on top of Alder dam, it was hard for me to imagine that this awesome dam was steadily approaching failure as sediment built up below the lake surface. This sediment was eroded from the glacial slopes of Mount Rainer. Then, it was washed down by the Nisqually River. By 2011, it had filled in about 15% of the previous reservoir volume (Czuba et al., 2012). That percentage continues to increase, simultaneously decreasing the room available to store water and adding more and more pressure to the back of the dam. Eventually, if we do nothing, one of those tiny grains of sand will be the grain that breaks the dam’s back, sending a flood of water and sediment downstream.

Our next field trip was to see where the Glines Canyon Dam and Elwha Dam once stood. They were smaller than Alder Dam. Still, the Glines Canyon Dam holds the title of largest dam removal, ever, anywhere. These dams were both built on the Elwha River in the early 1900s. For almost a century, they trapped sediment and disconnected the upper and lower Elwha. Fortunately, the Elwha River drains Olympic National Park, so pesticides, radioactive waste, and fertilizer (and flip flops) did not majorly accumulate in the reservoir. The dams were perfect candidates for removal when the cost of destroying salmon habitat finally overtook the benefit of controlling floods and drawing hydropower. In a sense, the stars were aligned and the dams were set to be removed.

When the Elwha River dams were built in the early 1900s, their construction plans didn’t include fish ladders. They blocked spawning salmon that tried to swim upriver and effectively removed 90% of the previously available habitat (Pess et al., 2008).

The process was not easy. In 1992, the Elwha River Ecosystem and Fisheries Restoration Act was passed by the U.S. Congress. The project was predicted to take 20 years and cost up to $203 million (Wunderlich et al., 1994). Sediment posed the most significant environmental challenge. Releasing all the trapped sediment at once could smoother downstream habitats. Researchers predicted that the sediment would fill in river channels, leaving less room for water flow and causing more severe floods. Nevertheless, the challenge to remove the dams and restore the diverse ecosystem was accepted. In 2014, over three decades after the restoration act was passed, the last bit of removable concrete was hauled away from the Elwha River.

My generation has inherited a dam problem. When I was first presented with this challenge, while standing on top of Alder Dam, I looked at the students’ faces. They seemed unconcerned. When I looked at those same faces at the end of the trip to the Elwha Dams, they displayed anxiety and motivation. Beth Fancher, one of the students, said that she had heard about the Elwha dam removal project before going on the field trip, but “actually seeing [the] physical effects [of dam removal] on the natural landscape is shocking.” The complexity that wraps and binds the issues of dam removal is not going to go away, but the dams still must.

I am starting a series of posts to explore the complexities of dam removal, using the Elwha as my case study. My next post will delve into what the 19 million cubic meters of sediment that had been locked up behind the Elwha dams (Czuba et al., 2011) did when it was finally released from captivity. Teaser: it wreaked havoc.



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