As water exits the Gold King mine, it flows into a system of four treatment ponds, which provide retention time to allow the pH to adjust. Lime is sometimes added to assist in the pH adjustment prior to discharge to Cement Creek.

The Gold King Mine Spill, in which actions by the EPA caused about three million gallons of contaminated wastewater to accidentally flow into Cement Creek, a tributary of the Animas River, whose water eventually winds up in the Colorado River, endangered people's health, threatened massive pollution, and caused the environmental agency to take numerous steps to prevent further damage.

In a statement released by the EPA, they admit that on August 5, their investigation of the mine near Silverton, Colo., to "assess the on-going water releases from the mine, treat mine water, and assess the feasibility of further mine remediation," caused pressurized water to begin leaking above the mine tunnel which led to the massive spill.

The rest of their statement reads:
"EPA is working closely with first responders and local and state officials to ensure the safety of citizens to water contaminated by the spill. The agency has activated its Emergency Operations Center to ensure coordination among its regions, laboratories and national program offices in Washington, D.C. EPA is closely coordinating with the officials in Colorado, New Mexico, Utah, Southern Ute tribe and Navajo Nation. EPA is taking the lead on efforts to contain the leak and flow from the mine is now controlled. EPA has also deployed federal On-Scene Coordinators and other technicians in Colorado, New Mexico and Navajo Nation to assist with preparations and first response activities in these jurisdictions. EPA is sharing information as quickly as possible with the community as experts work to analyze any effects the spill may have on drinking water and public health."

EPA's efforts included building treatment ponds and diversion channels, stabilizing the road to the mine, and ongoing monitoring of river water to assure water quality is remaining at pre-event levels.