A contractor-triggered EPA mine drainage accident released three million gallons of toxic water into the Animas River, affecting Colorado, New Mexico, Utah, and the Navajo Nation.
Key Facts
- Volume spilled
- 3 million US gallons (11,000 cubic metres)
- Spill date
- August 5, 2015
- Flow rate during remediation
- 500–700 US gal/min gal/min
- States affected
- Colorado, New Mexico, Utah, and Navajo Nation
- Key contaminants
- Cadmium, lead, arsenic, beryllium, zinc, iron, copper
- Responsible agency
- U.S. Environmental Protection Agency (EPA)
By the Numbers
Location
Cause → Event → Consequence
EPA personnel and contracted workers from Environmental Restoration LLC were attempting to drain ponded water near the entrance of the Gold King Mine. During this operation, contractors accidentally destroyed the plug retaining water trapped inside the mine, breaching a tailings dam and triggering an uncontrolled overflow.
On August 5, 2015, the breach released approximately three million US gallons of acidic mine waste water and tailings into Cement Creek, a tributary of the Animas River. The contaminated water contained heavy metals including cadmium, lead, arsenic, beryllium, zinc, iron, and copper, and flowed into the broader San Juan and Colorado River watersheds.
The spill affected waterways across Colorado, New Mexico, and Utah, as well as the Navajo Nation. The EPA was widely criticized for failing to warn downstream states until a day after the event. The agency accepted responsibility but refused damage claims under sovereign immunity. Governor Hickenlooper declared a disaster zone, and the incident heightened national attention to toxic drainage from abandoned mines.