Science & Technology



'Like a World War II battlefield': How one of Northern California's most polluted properties may finally be cleaned up

Paul Rogers, The Mercury News on

Published in Science & Technology News

The legacies of California’s 1849 Gold Rush and the relentless search for gold that continued decades later are well known: the rise of San Francisco; statehood; Wells Fargo; Levi’s jeans; a Bay Area football team named after the fortune-seeking miners.

But along the shores of Clear Lake, just north of Napa Valley’s famed wineries, is another gold-rush legacy: toxic pollution.

From the 1860s until it closed in 1957, the Sulphur Bank Mine was one of the largest mercury mines in the United States. Gold miners in the Sierra Nevada used the mercury dug from its deep tunnels and craggy cavities to separate gold from the ore that held it.

Today, what’s left is a rocky, open pit as large as 20 football fields, filled with murky blue-green acidic water 90 feet deep and surrounded by a barbed wire fence adorned with “Danger EPA Superfund Site” signs. Massive piles of mining waste around the rest of the 160-acre landscape enough to fill 250,000 dump trucks are contaminated with arsenic, mercury and other toxics.

“It’s got kind of a bomb-crater character to it,” said Jeffrey Mount, former chairman of the geology department at UC Davis. “It’s like the surface of Mars. It’s highly polluted. Nothing much grows there. The whole place looks like a World War II battlefield.”

Now a major effort has begun to clean up the historic mess and reduce health threats to people who have called the area home for thousands of years.


In November, the U.S. Environmental Protection Agency approved a $94 million project to clean the mine site. The plan, funded in part by the bipartisan infrastructure law that President Biden signed in 2021, is the largest cleanup funded by the government at any of the 97 Superfund sites in California, a list that includes many of the most polluted properties in the state.

Scientists say the abandoned mine’s pollution is leaching into Clear Lake, only 500 feet away. The pollution is contaminating bass and other fish in one of the oldest and largest freshwater lakes in California, and endangering the health of those who eat them.

Compounding the threat, directly adjacent to the site is the Elem Indian Colony, a Native American community that has been exposed to the toxins for generations.

“This is one of the most serious mercury sites, if not the most serious mercury site, in California,” said Carter Jessop, the EPA’s project manager for the cleanup. “It has contaminated a lake that is of profound tribal significance and regional significance. It has dramatically diminished the lake.”


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