The 2015 Gold King Mine waste water spill is a 2015 environmental disaster at the Gold King Mine near Silverton, Colorado. On August 5, 2015, EPA personnel along with workers for Environmental Restoration LLC (a Fenton, Missouri, company under EPA contract to mitigate pollutants from the closed mine) caused the release of toxic wastewater when attempting to add a tap to the tailing pond for the mine.

[2] Before the incident, the local jurisdictions refused Superfund money to cleanup the regions’ derelict mines due to a fear of lost tourism. Following the spill, the local government of Silverton decided to accept Superfund money to fully remediate the mine.

Workers accidentally destroyed the dam holding back the pond, spilling three million US gallons (11 ML) of mine wastewater and tailings, including heavy metals such as cadmium and lead, and other toxic elements, such as arsenic, into Cement Creek, a tributary of the Animas River in Colorado.[The EPA was criticized for not warning Colorado and New Mexico until the day after the wastewater spilled.

The EPA has taken responsibility for the incident, and the governor of Colorado, John Hickenlooper, declared the affected area a disaster zone. The spill affects waterways of municipalities in the states of Colorado, New Mexico, and Utah as well as the Navajo Nation. As of August 11, acidic water continued to spill at a rate of 500–700 US gal/min (1.9–2.6 m3/min) while remediation efforts were underway.

https://en.wikipedia.org/wiki/2015_Gold_King_Mine_waste_water_spill