The largest hydroelectric dam demolition project in the United States is about to begin

The largest hydroelectric dam removal project in US history will begin next year in Northern California.

Iron Gate hydroelectric dam in California.

MSN reported that the project to demolish the Iron Gate hydroelectric dam on the Klamath River in Northern California, USA will begin in 2022. For more than 100 years, the Klamath river has been among the most important for fish. Back in the US, dams blocked the flow of traffic.

According to the BBC, it's hard to say how important the fishery was to the Yurok people who have lived for millennia in rural Northern California. However, this livelihood has dwindled in the decades after the Klamath River, which flows through the tribe's territory, was blocked to build a hydroelectric dam. But now, after years of tense negotiations, Yurok's luck has turned, with the largest dam removal project in US history given the green light.

How to remove the dam

Klamath River Renewal Corporation – the nonprofit organization tasked with overseeing dam removal – presented how the Iron Gate Dam will be removed. Accordingly, the entire reservoir will flow through the dam's old diversion tunnel. Once the diversion tunnel is clear and reinforced with concrete, the dam gates will be opened.

The 72 million cubic meter wall of water behind the dam is gradually drained to prevent flooding downstream. The steel plates piled along the top of the dam along with the tanks below the dam were removed.

Millions of kilograms of compacted rock and gravel (with a core of impermeable clay) were removed by excavators, moving 7.500 cubic meters of rock per day, later increasing to 16.000 cubic meters/day.

Excavators and excavators break the upstream cofferdam, preventing floods by digging a series of trenches into the rock bed. Demolition of tunnels, powerhouses, and other structures with hydraulic breakers, hoes, drilling, and blasting.

The goal is for the Klamath River to be clear by the end of 2023. When everything is complete, the topsoil will be replaced, then planted with native grass, trees, shrubs, and other vegetation.

Illustration of Iron Gate Dam demolition. 

Why must dams be removed?

Even though hydropower is considered “clean,” dams are still not environmentally friendly.

“For the Yurok people, the fight to remove dams is more than just an environmental issue,” said Yurok Tribal Vice Chairman Frankie Myers – who has been at the forefront of the fight to remove dams on the Klamath River since 2002. it is a fight for our existence.”

The Klamath River was once home to the third largest salmon species in the United States - adult salmon would swim upstream, returning to their home river to spawn. Now, the amount of fish returned is only a small fraction of what it was before.

Dams built on the Klamath River have been identified as one of the causes of the decline in salmon numbers.

A total of eight hydroelectric dams were built across the river from the early 1900s until 1962. Their presence caused marked changes in salmon populations on the Klamath and elsewhere.

"Whenever you build a dam on a river, it always has terrible effects: It cuts the flow into two completely separate parts" - BBC quoted Mr. Michael Belchik, a fisheries biologist. senior member of the Yurok tribe and a tribal member with decades of experience in restoring fish stocks, explains.

Reservoirs behind dams are also responsible for significant accumulations of toxic algae – which thrive in warm, nutrient-rich stagnant water. In large enough quantities, it is harmful to human health.

The solution that the Yurok and a coalition of other tribes and environmental groups have long advocated is to remove four of the eight dams on the lower Klamath River.

After difficult negotiations, PacifiCorp (the company that operates the dams) and 40 stakeholders, including tribes and the California state government, signed an agreement in 2010.

According to Klamath River Renewal Corporation, the simultaneous removal of four dams with a total height of 125m makes this the largest dam removal project in US history.

This is also considered the most expensive project, up to nearly 450 million USD.

The result will be 640km of river flow restored to habitat for salmon and other migratory species such as rainbow trout and Pacific lamprey.

According to thiennhien.net