Over the past century, the United States has led the world in dam construction. There are at least 90,000 dams over six-feet tall in this country, and over 2 million shorter than six feet. More than a quarter have passed their 50-year average life expectancy; by 2020, that figure will reach 85 percent. On average, we have constructed one dam over 6 feet tall every day since the signing of the Declaration of Independence.

Dams are set in place for irrigation, electricity generation, water storage … they have lots of society benefits. But it’s undeniable that dams cause significant harm to natural ecosystems. They prevent fish migration and limit access to spawning habitats. They decrease the flow of the river. Many fish such as salmon and river herring depend on steady flows to guide them. Irregular releases of water destroy natural seasonal flow that signals the start of growth and reproduction cycles in certain species. They trap massive amounts of sediment, blanketing rock riverbeds where fish spawn. Larger objects, like rocks and logs, get trapped, keeping them from creating complex habitats downstream. Sometimes the river is stopped entirely behind the dam for periods of time, leaving the riverbed dry.

In the reservoir, the water gets warmer than it should, affecting sensitive species and leading algae to bloom. When water is released, it’s often released from the deep, cold, oxygen-deprived depths.

Once past the half-century mark, dams begin to decay. The earth around them erodes and seeps, gates rust, concrete loses tensile strength, and the accumulating settlement reduces the capacity of reservoirs. A feeble dam could fail, causing dangerous flooding.

As costs to maintain dams rise, the economic return is decreased. Many older dams are obsolete. In few other places were these effects so evident than on the Elwha River in the northwest corner of Washington, where 100lb salmon once ran freely upstream from the Pacific Ocean. For millennia these fish thrived in the river and provided food for the indigenous people who lived along its banks until two dams were constructed.

On today’s episode of America’s National Parks, the removal of the dams on the Elwha river in Olympic National Park. And if you think it just takes a little dynamite, it doesn’t.

Here’s Abigail Trabue.

In the late 1800s, a growing nation looked to the Northwest to supply the lumber needed to build new cities. Thomas Aldwell was the first to see an opportunity for economic gain in the taming of the Elwha River, making plans to harness the water to generate electricity. With the financial backing of investors, he bought land along the river and began construction of the Elwha Dam in 1910. A state law demanded fish passage devices be built into dams, but Fish Commissioner Leslie Darwin offered to waive that provision if Aldwell built a fish hatchery adjoining the dam. It was abandoned by the state in 1922.

The concrete dam was secured to the walls of the canyon, but not the underlying bedrock, causing the foundation to blow out in 1912 shortly after the reservoir (called Lake Aldwell) filled. It was plugged by adding fill material to the river below and above of the dam.

The Elwha Dam became operational in 1913, bringing electricity to a remote area, spurring economic growth. As demand increased, two additional turbines and a second powerhouse were installed, and then, another dam eight miles upstream in Glines Canyon. Its narrow passage and high bedrock walls promised a large energy yield.

Prior to the dam construction, all five species of Pacific salmon ran the Elwha, along with other river-spawning fish. The failure to build fish ladders left the River with only five miles of available habitat for spawning. Over time, fish populations diminished to less than 10% of their early 1900s levels. The dam flooded lands sacred to the indigenous people of the area, who have long identified with the river, the salmon, and the land.

For decades, experts agreed that removing the two dams were essential for the watershed, in particular, for its trout and salmon. But the idea of eliminating two sources of inexpensive electricity was universally panned by the public.

“Thirty years ago, when I was in law school in the Pacific Northwest, removing the dams from the Elwha River was seen as a crazy, wild-eyed idea,” Bob Irvin, president and CEO of the conservation group American Rivers told National Geographic.

In the 60s, tribes began to protest the loss of the fishing rights promised to them by a federal treaty signed in the 1800s. In 1979, the Supreme Court ruled that Washington tribes were entitled to half the salmon catch in the state. In the wake of the court victory, the tribes began to partner with conservation groups to fight for the restoration of salmon runs and the removal of the Elwha River dams. The Olympic Peninsula had long ago been connected to the regional power grid, and the dams now provided only a small portion of the power used by its residents and industry.

The missing fish passage structures that had never been installed would cause a reduction in energy creation at the dams, sending the power they produce soaring above market prices.

In 1992, the federal government purchased the dams from the timber companies that owned them and ordered a study of removing them. Two decades of planning began for what would be the largest-ever dam removal project in the world.

Still, the timber industry and local communities opposed the demolition, and Senator Slade Gorton blocked federal funding until he was voted out of office in 2000.

The dams would have to be taken down in several stages, allowing for a relatively gradual release of the 27 million cubic yards of sediment that had built up over the course of a century. If the sediment flowed too quickly, it would damage the existing riverbed downstream, and could affect the water quality. Two treatment facilities would be built to protect local water supplies.

Different demolition methods would be used at the two dams because of their unique structural requirements. At the Glines dam, an “in the wet” process would be used, meaning the dam would be removed without diverting the water around it. First, water levels in the Lake Mills reservoir were lowered to the bottom of the spillway gates. Then, on September 15, 2011, giant barge-mounted hydraulic hammers began to remove the top 17 feet of the dam down to the waterline. The next 173 feet would be removed using a notching process. The dam was “notched down” on alternating sides, creating temporary spillways that would gradually drain the reservoir. Demolition was regularly paused for weeks at a time to allow the sediment to run through, and to avoid salmon spawning periods. Other structures were removed during these windows of halted deconstruction.

The Elwha dam would be removed “in the dry” by diverting water around it through a newly excavated channel. The first step was to lower the reservoir’s water level by using the existing water intakes and spillways by approximately 15 feet. The process began on June 1, 2011 following the closure of the powerhouse. The temporary channel was then excavated through the left spillway to allow Lake Aldwell to be further drained. Temporary dams were then installed to direct reservoir outflow into the temporary diversion channel. This allowed the remaining water immediately behind the dam to be pumped out. The fill material behind the dam could then be removed under dry conditions, followed by the concrete dam itself using diamond-wire saws.

35,000 cubic yards of concrete–more than half the amount used to construct the Empire State Building–would need to be broken up and recycled, along with hundreds of tons of metal.

Once the dam was deconstructed, the temporary dams were removed, allowing the river to flow through its original channel for the first time in a century. Earth fill and crushed bedrock was used to reshape the slopes around the dams to their original contours.

On August 26, 2014, the last 30 feet of Glines Canyon dam were reduced to rubble with a final blast of explosives. The largest dam removal in history was complete. The national park service began the process of reintroducing plants to the now barren reservoir bed, and tagging and tracking salmon.

Over the course of the last few years, the sediment has washed downstream, rebuilding riverbanks and gravel bars and creating some 70 acres of new beach and riverside habitat for creatures of all types. Shellfish began to return to the mouth of the river.

Salmon populations continue to recover, and scientists expect the whole food chain to benefit. Almost as soon as salmon returned to the river, birds began to follow the fish and to eat salmon eggs and young, providing essential nutrients. Bigger birds are bearing more young, and moving in to the area permanently. Elk stroll and munch on the vegetation buffet where there used to be a lake.

The river that emerged when the dams were removed didn’t follow orderly down a forgotten channel, however. It was chaotic and wild. Its movements were difficult to anticipate and useless to control. Logs tumble and stack, building complexities into the river’s flow. It has destroyed two campgrounds and washed out a road. But the channel is stabilizing, and the river has gained a teal green color it hasn’t seen in 100 years.

It’s rare that humans have the opportunity to set a river wild again, but on the Elwha, it happened.

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Dams continue to be a hot-button issue along many important waterways, but the public is getting more and more behind their removal. In Washington, the four lower Snake River dams are in the crosshairs of conservationists who are looking to preserve more salmon runs. A recent poll shows that the majority of Washington voters would rather see increased wild salmon runs than preserve the dams, even if it means paying a few dollars more a month on their electric bills.

Visiting Olympic National Park you’ll find a million acres full of several different ecosystems, including glacier-capped mountains, old-growth temperate rain forests, and over 70 miles of wild coastline. It’s a World Heritage Site and an International Biosphere Reserve, serving as a living laboratory for scientists and students, as well as an incredible natural playground for visitors. Millions of people visit Olympic each year to experience its beauty, diversity, and many opportunities for adventure, exploration, and recreation.

Rustic cabins, historic lodges, and charming resorts are available for visits, along with 14 National Park campgrounds, only two of which accept reservations.

Olympic is very large and there are no roads that cross the park, so it takes time to get everywhere, and you need to plan accordingly. June through September, when the weather is mild, are the busiest time of year.

This episode of America’s National Parks was written by me, Jason Epperson, and narrated by Abigail Trabue. If you enjoyed the show, we’d love a 5-star review wherever you listen to podcasts. Don’t forget to hit the subscribe button, and follow us on Facebook, Twitter, and Instagram. Just search “National Park Podcast.” You can also join our new America’s National Parks Facebook group for national park lovers. We’ll link to all of our social media, as well as National Park Service resources, in the show notes at National Park Podcast dot com.

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