The Animas River is the cultural soul of this patch of southwestern Colorado, a sort of moving Main Street that hosts multiple floating parades a year and is typically bustling with rafters and kayakers. Schoolchildren study the river. Sweethearts marry on its banks. Its former name, given by Spaniards, is el Río de las Ánimas, the River of Souls.
But since Wednesday, the Animas has been grievously polluted with toxic water spilled from one of the many abandoned mines that pockmark the region — a spill for which the Environmental Protection Agency has claimed responsibility, saying it accidentally breached a store of chemical-laced water.
Testing by the E.P.A. — an agency typically in the position of responding to toxic disasters, not causing them — found that the wastewater spill caused levels of arsenic, lead and other metals to spike in the Animas River.
On the day of the accident, a team from the agency had been investigating an abandoned mine about 50 miles north of here. Called the Gold King, it is roughly 1.5 miles long and about 700 feet tall at its highest point. The mine had been abandoned for nearly a century, but between roughly 1890 and 1920 it produced 350,000 ounces of high-grade gold, according to its owner.
For years, the Gold King has leaked toxic water at a rate of 50 to 250 gallons a minute. The agency had planned to find the source of the leak in the hope of one day stanching it. Instead, as workers used a backhoe to hack at loose material, a surprise deluge of orange water ripped through, spilling into Cement Creek and flowing into the Animas. The burst did not injure workers.
In his first interview since the spill, the owner of the mine, Todd Hennis, said the spill was probably the fault of another mine company — the Sunnyside Gold Corporation — that had built retention walls inside an abandoned mine near the Gold King, part of an old cleanup agreement with the federal government. Once the Sunnyside mine filled with wastewater, the water probably spilled into the Gold King, and then into the Animas, Mr. Hennis said.
He urged Sunnyside’s parent company, the Kinross Gold Corporation, to clean up the mess. “They’ve got to step forward and be responsible,” he said of Kinross. A spokesman for Sunnyside, Larry Perino, said the company had no role in Gold King spill.