An abandoned mine in Shasta County that produces about 1,200 times the legal limit of toxic substances has been designated a Superfund cleanup site by the U.S. Environmental Protection Agency.
The Afterthought mine, located about 25 miles east of Redding just off Highway 299, was placed on the list Wednesday because of metals and highly acidic water flowing from the mine and nearby Little Cow Creek, a tributary of the Sacramento River, the EPA said.
As miners dug into the hills near the mine, minerals exposed to the air and water turned into an acid that continued to flow from the tunnels for decades, said John Hillenbrand, project manager for the EPA.
The solution coming out of the mine is “pure acid,” similar to battery acid, he said.
“So it's really nasty stuff. And then it leaches all the metals out, and they come out of the mine tunnel and dump them into the river, in this case little Cow Creek gets the full brunt of it. So this is acid mine drainage, right? And it just comes out every day, 24 hours a day. It varies in quantity, 250 gallons a minute or more can come out of this thing and go right into the creek,” Hillenbrand said.
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In addition to the acid, the water is “mainly full of copper and cadmium, zinc and arsenic,” Hillenbrand said.
“Downstream from the site, surface water and sediments in Little Cow Creek are contaminated with cadmium, copper, and zinc at concentrations approximately 100 times, 1,200 times, and 1,000 times, respectively, the California Toxics Rule Water Quality Criteria for acute risk,” according to a description of the mine on the EPA’s website.
Designating the mine as a Superfund site puts the area on the path to cleanup, Hillenbrand said. The agency will study the mine and tunnel flows over the next three to five years to determine the best method for treating the water.
“But that’s one of our goals: We try not to build things that require a lot of pumps, people, and electricity, because that’s expensive. So if we can spend a little bit of extra time and make it passive — like natural bacteria filtration systems — then we’d rather do that,” Hillenbrand said.
The treatment could take hundreds of years, he said, “because this place will never stop generating water, ever. It will just go on forever, for thousands of years. So we want to try to do it right.”
In addition to cleaning the water, contaminated rocks at the site must also be removed and covered so they no longer pose a threat to the environment, he said.
In Little Cow Creek, the water remains harmful to fish and people should not drink it or come into contact with it in the immediate area, Hillenbrand said. The water is diluted by the creek downstream and is not a problem for people. People should not cross the creek from Highway 299 to where the water flows from the mine, he said.
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“The bank closest to the mine, probably the 10 percent or 15 percent along the edge, turns orange when the water mixes acid with the river. So if I were a fish, I wouldn't want to swim there. I'd swim on the other side of the creek,” Hillenbrand said.
The current owners of the property did not develop the mine, so they do not have to pay for the cleanup, he said. Taxpayers are footing the bill for the cleanup, he said. Hillenbrand did not have an estimate of the cost to treat the water.
The Afterthought Mine will be the second Superfund site in the county. The Iron Mountain Mine, which sits on 4,400 acres northwest of Redding, has been on the EPA's list since 1983.
Hillenbrand said the facilities used to treat the water at Iron Mountain are more extensive and intensive than will likely be needed for the Afterthought mine.
The EPA's web pages on the Iron Mountain Mine state: “Prior to cleanup, acidic, metal-rich waters virtually destroyed local creeks and caused periodic fish kills in the Sacramento River.”
According to Hillenbrand, the contamination at the Iron Mountain mine is much more serious than at the Afterthought mine.
“There's nothing worse than Iron Mountain Mine in the entire country. Iron Mountain Mine is about 1,000 times bigger than this mine. It (the water in the mine) has a negative pH, so it's a pH of minus 2 or 3. It's unbelievable how bad it is,” he said, describing the acidity of the mine water.
According to the World Health Organization, the pH of most drinking water is between 6.5 and 8.5.1
The Afterthought Mine was first developed in 1862 and remained in operation until 1952. Remains of the mine, including wooden structures, can still be seen from Highway 299 in the small community of Ingot, east of Redding.
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According to the EPA, 166,424 tons of ore, 10,730,580 pounds of copper, 23,635,840 pounds of zinc, 1,738,300 pounds of lead, 923,653 ounces of silver and 4,992 ounces of gold were recovered from the mine.
The remains of an inactive smelter associated with the mine, called the Afterthought Smelter, are located about a mile downstream from the mine site, the EPA said.
Mary Rickert, a Shasta County supervisor whose district includes the mine, said she had heard about the proposed cleanup and was pleased the mine had been designated a Superfund site.
She said Little Cow Creek, which receives the toxic mine drainage, “flows into Cow Creek and then goes through a lot of residential properties, and it impacts a lot of people, and your cattle drink out of the creeks. So I think it's something that's probably long overdue.”
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This article originally appeared on Redding Record Searchlight: Shasta County Mine With 'Pure Sour' Water Now an EPA Superfund Site
