Mercury contamination in Clear Lake a legacy of mining
CLEAR LAKE - Standing on a bluff overlooking Clear Lake, it’s possible for Elem Indian Colony elder Jim Brown III to envision a time more than 10,000 years ago, when humans first arrived and settled the area.
“We are the oldest tribe classified as Pomo ever created,” the tribal historian said, explaining there were large geysers and hot springs close to the lake “where our people did our sweats. Thousands traveled to the place.”
But what was once an area of spiritual significance is today a toxic dump. For more than a century, an abandoned mine named Sulphur Bank has leached tons of mercury into Clear Lake and poisoned not only the food chain and the fish the tribe traditionally relied on, but possibly the people, too.
Fifteen years and several cleanup operations after it was made a high priority by the U.S. Environmental Protection Agency, Sulphur Bank still defies efforts to stop the contamination.
This spring, the EPA expects to complete a feasibility study describing its latest evaluation and possible cleanup method that will be available for public review and comment.
Clear Lake is a poster child for mercury contamination, but is not unique. The state has identified roughly 150 “mercury impaired” reservoirs including Lake Sonoma, Lake Mendocino, Lake Berryessa and Lake Pillsbury. Even Spring Lake in Santa Rosa is on the list for future study, due to concerns about mercury levels in fish.
Contaminated runoff from abandoned mines impacts tens of thousands of acres of public and private land, along with groundwater and hundreds of streams, rivers and lakes, according to the California Department of Conservation.
Abandoned mines release a host of toxins, including arsenic, asbestos, lead and other chemicals. But mercury is the most insidious, accumulating in fish that become hazardous to eat.
Clear Lake, a 60-square-mile body of water that flows into Cache Creek, the Sacramento Delta and eventually San Francisco Bay, has other periodic problems that include toxicity from blue-green algae blooms, clogging from hydrilla and invasive plant species.
The difference is mercury, transported via waterways, spreads beyond the lake and into the aquatic food chain.
“It’s not just the population of Clearlake and 65,000 people. It’s a potential contaminant to several million people,” said Lake County Supervisor Jim Steele, a freshwater ecologist and retired branch chief of the Department of Fish and Game’s science division.
Once mercury gets into the water it settles to the bottom where bacteria transform it to organic, highly toxic “methylmercury” accumulating in shellfish and fish that are unsafe for humans to consume.
A tarnished legacy
Sulphur Bank Mercury Mine is part of the most visible evidence of California’s mining and Gold Rush legacy, which according to a state report includes more than 47,000 abandoned mines statewide with 11 percent - about 5,170 - presenting environmental hazards.
Today, it’s a Superfund site where the federal government has spent more than $60 million on cleanup costs. The figure is expected to exceed $100 million in total to fix the problem, but with no certain funding or end date for the project.
The Sulphur Bank mine, located on an eastern arm of Clear Lake near Clearlake Oaks, is one of three mercury mines among California’s 97 Superfund sites, which also include gold, copper and other mineral extraction operations. It’s one of two ongoing Superfund sites in the North Bay, a federal designation for cleaning up some of the nation’s most contaminated lands.
The abandoned mine pit next to the 50-acre Indian reservation has become a huge, 90-foot-deep pond topped with an orange-green sheen, occasionally belching a sulfurous, rotten-egg odor.
It’s what remains of an operation that started as a sulfur mine in the 1860s. Demand shifted in the 1870s to mercury, primarily to extract gold and silver from ore deposits throughout the West.
The Sulphur Bank mine, once one of the largest producers of mercury in California, has been inactive since 1957. But approximately 150 acres of mine tailings and waste rock remain from what was piled into the lake and close to shore. Mercury, with suspected carcinogens arsenic and antimony, seeps into the lake aided by groundwater springs.
“They can’t stop it. They can slow it down,” Karola Kennedy, the environmental director for the Elem Indian Colony, said of the containment effort to date.
About 17 different water companies, including Clearlake Oaks County Water District about a half-mile away, draw from Clear Lake, but drinking water supplies generally are safe.