Proposed Dams Near Seismic Fault

Residents and activists already concerned about the devastating impact proposed dam projects could have on southern Chile’s pristine wilderness, now have a new argument for why it is simply a bad idea to dam Patagonia’s rivers: earthquakes.

September 4, 2007

Residents and activists already concerned about the devastating impact proposed dam projects could have on southern Chile’s pristine wilderness, now have a new argument for why it is simply a bad idea to dam Patagonia’s rivers: earthquakes.

In recent weeks, the towns of Pueto Aysén and Puerto Chacabuco in southern Chile’s Region XI have been jolted by an unusual spate of seismic activity that continues to rock the area. In the last week of January alone, seismologists recorded an astounding 1,700 tremors—only a small but still alarming number of which were noticeable. A few of the small quakes registered as high as 6 on the Mercalli scale. Locals initially feared a repeat of the devastating 1991 eruption of the nearby Hudson Volcano, which was preceded by a similar cluster of tremors and quakes.

Authorities, however, have since come up with another theory to explain the tremors. A team of scientists dispatched to the area in late January concluded that the quakes are likely being caused by underground magma flow in the nearby Aysén fjord. According to the experts, the magma, which is pressuring a subterranean tectonic plate, could eventually push its way to the surface and form a relatively small volcanic cone on the seafloor of the fjord.

The scientific team—made up of a Universidad de Chile seismologist, a geologist from the National Mining and Geologic Service and a volcanologist from the National Emergency Office—identified the epicenter of the tremors as being approximately 12 miles northwest of Puerto Chacabuco.

Xstrata's project map superimposed on map of region with the epicenter of the quake at left. (Courtesy:

That, say some area residents, is dangerously close to the site of a 600-megawatt hydroelectric dam the Swiss mining company Xstrata—working through its local affiliate Energía Austral—plans to build on the Cuervo River. Xstrata, which has already submitted the requisite Environmental Impact Study, is looking to begin construction on the $600 million project sometime next year.

During a community forum organized earlier this month by journalist Patricio Segura and architect Peter Hartmann, participants expressed major concern about the Xstrata project’s proximity to the estimated epicenter of the quakes.

“It seems dangerous to me,” said Paola Bustamante, a teacher from Puerto Aysén. “It’s terrifying to me to think about earthquakes plus dams. With the appearance of this new variable, I think we need to take an even deeper look (at this proposal) and tell people the truth, not hide anything.”

“The people are really worried about the issue of quakes,” said Hartmann, who also heads the regional office of an environmental group called the Committee for the Defense of Flora and Fauna (CODEFF). “The problem is that the epicenter of the recent quakes and the volcano that might form there are exactly in front of the place where they want to build the dam. This represents a risk even for the company.”

Segura and Hartmann are both members of a coalition calling itself the Citizen Coalition for the Aysén Life Reserve (Coalición Cuidadana por Aysén Reserva de Vida CCARV). The coalition represents a wide range of both local and national organizations, including Hartmann’s CODEFF; a group calling itself the Defenders of the Spirit of Patagonia; and the Santiago-based environmental NGO, Ecosistemas.

Together the groups are opposing not only Xstrata’s proposed Cuervo River dam, but also other pending Region XI hydroelectric initiatives, chief among them Endesa-Colbún’s “Aysén Project.”

"No More Dams," protest march led by the National Tehuelche Youth Group. (Courtesy: Agrupación Nacional de Jovenes Tehuelches)

Considered the most ambitious energy endeavor in Chile’s history, the estimated $4 billion Aysén Project involves plans to build two dams on each of Region XI’s two biggest rivers: the Baker and the Pasqua. Together these dams would generate an estimated 2,400 megawatts. Backers of the project say this would go a long way toward meeting Chile’s growing energy needs.

In order to generate that electricity, however, the companies behind the plan—Spanish electricity giant Endesa, and Colbún, a Chilean entity that is part of the Grupo Matte—will need to flood approximately 56 square mile of wilderness area.

There’s also the question of how the companies plan to transport that electricity from Region XI to the central part of the country—mainly, Santiago—and to the Chile’s massive mining projects, where consumption is highest. The plan so far is to build a 1,243-mile transmission line—the world’s longest—that would literally cut through acres upon acres of both protected and unprotected wilderness area.

“Patagonia is one of the planet’s last great wildernesses,” according to Jacob Scherr of the U.S.-based National Resources Defense Council (NRDC). “What we’re looking at is a plan to basically build dams on every major river in the region, and to build a 1,200-mile transmission line that would cut a broad swath through a number of wilderness areas and national parks.”

“Unless the Government of Chile steps up and pardons Patagonia,” he added, “the area will be electrocuted. It will be destroyed. We’re hoping President (Michelle) Bachelet will give a pardon to Patagonia.”

Benjamin Witte is a writer based in Santiago, Chile. He can be reached by email at: benwitte(AT)

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