The orange-colored discharge started flowing from the Gold King Mine near Silverton into Cement Creek and then the Animas River on Wednesday and prompted heath officials Thursday to warn agricultural and recreational water users to avoid the river.
EPA confirmed Friday the discharge from the mine contained heavy metals and metalloids including lead and arsenic, along with cadmium, aluminum, copper and calcium, but the agency didn't immediately discuss amounts or health risks.
Officials in New Mexico are angry the U.S. Environmental Protection Agency did not informing them soon enough about the pollution floating downstream.
New Mexico's environment secretary, Ryan Flynn, said Friday that the EPA downplayed the danger the contamination posed to wildlife, saying that potential harm can't be known until the contents of the wastewater and their concentrations are known.
The San Juan Health Department says the acidic mine water associated with the release contains high levels of sediment and metals. Durango has shut down water intakes until the contaminated water has passed, but the city says tap water is safe to drink.
On Friday aternoon, EPA released more details about how it says the pollution was released:
On August 5, 2015, EPA was conducting an investigation of the Gold King Mine. The intent of the investigation was to assess the on-going water releases from the mine and to treat mine water and to assess the feasibility of further mine remediation. The plan was to excavate the loose material that had collapsed into the cave entry back to the timbering. During the excavation, the loose material gave way, opening the adit (mine tunnel) and spilling the water stored behind the collapsed material into Cement Creek, a tributary of the Animas River.
La Plata County Emergency Management says the plume reached the outskirts of Durango at about 7:30 p.m. County Sheriff Sean Smith says that the river has been closed to tubers, rafters and kayakers in the county and won't reopen until the river is deemed safe.
The Durango Herald reports that Colorado Parks and Wildlife has placed four cages of fish along the river to see how the pollution affects them.
The mineral flow in the Animas River is now less than a couple of miles north of Durango. pic.twitter.com/1l4F3hhvSV— jerry mcbride (@jerryphotog) August 6, 2015
Sheriff has officially closed the Animas River! pic.twitter.com/NQ24p0Q0fa— John Livingston (@jlivi2) August 6, 2015
Editor's note: An earlier version of this story referred to arsenic as a heavy metal. Arsenic is a metalloid. The error has been corrected.