Last week the EPA was trying to stanch leakage from a gold mine — not worked since 1923 — but accidentally breached an underground reservoir of toxic water.
The orange-tinged slurry, which cascaded into Cement Creek and then into the Animas River, is now headed into New Mexico and Utah, but EPA officials say there has been no immediate evidence of harm to human or aquatic life.
While the short-term damage to wildlife appears minimal, the long-term consequences of the latest accident remain murky, with the full impact not likely to be known for weeks or months, the Colorado Department of Parks and Wildlife said, according to The Durango Herald.
What impact the sludge will have on the riverbed, for instance, remains a key unknown. Tests in Colorado are still being done, especially on the effect on insects that live along the waterway.
"It’s not something we can figure out instantly,” department spokesman Joe Lewandowski said Friday, The Durango Herald reported.
Although the effects of the spill remain uncertain, the president of the Navajo Nation, Russell Begaye, vowed Sunday that the EPA is “not going to get away with this,” local news station KOB reported.
The Navajo Nation sits on the borders between New Mexico, Arizona and Utah, and the Colorado River makes up part of the territory's northwestern border.
The Navajo Nation will recover “every dollar it spends cleaning up this mess and every dollar it loses as a result of injuries to our precious Navajo natural resources,” Begaye said.
“I have instructed Navajo Nation Department of Justice to take immediate action against the EPA to the fullest extent of the law to protect Navajo families and resources,” he told his constituents at a community meeting.
Navajo Nation Vice President Jonathan Nez told Al Jazeera that farmers along the San Juan River, a tributary of the Animas, have stopped irrigating their farms and could lose their crops in two weeks if they're not assured the water is safe.
"We are looking at holding people accounable here," Nez said. "And if the EPA is at fault here, then they're the ones who are going to be looked at by the Navajo Nation as the cause of this environmental catastrophe."
Nez added that the Navajo consider the San Juan River sacred and "how do you measure that in terms of dollars?"
Al Jazeera and wire services. Wilson Dizard contributed reporting