On August 5, 2015 over 3 million gallons of waste was released from Gold King Mine into Cement Creek which then flowed into the Animas River. The orangish colored plume moved over 100 miles downstream from Silverton, Colorado through Durango reaching the San Juan River in New Mexico and eventually making its way to Lake Powell in Utah (although the EPA stated that the leading edge of the plume was no longer visible by the time it reached Lake Powell a week after the release occurred).
Some of the impacts were immediate. No workers at the mine site were hurt in the incident but the collapse of the mine opening and release of water can be considered a near miss because there was potential for injuries. After the release, there were also potential health risks associated with the waste itself since it contained heavy metals.
Water sources along the river were impacted and there’s potential that local wells could be contaminated with the waste. To mitigate the impacts, irrigation ditches that fed crops and livestock were shut down. Additionally, the short-term impacts include closure of the Animas River for recreation (impacting tourism in Southwest Colorado) from August 5-14.
The long-term environmental impacts will be evaluated over time, but it appears that the waste may damage ecosystems in and along the plume’s path. There are ongoing investigations to assess the impact to wildlife and aquatic organisms, but so far the health effects from skin contact or incidental ingestion of contaminated river water are not considered significant.
“Based on the data we have seen so far, EPA and the Agency for Toxic Substances and Disease Registry (ATSDR) do not anticipate adverse health effects from exposure to the metals detected in the river water samples from skin contact or incidental (unintentional) ingestion. Similarly, the risk of adverse effects to livestock that may have been exposed to metals detected in river water samples from ingestion or skin contact is low. We continue to evaluate water quality at locations impacted by the release.”
The release occurred when the EPA was working to stabilize the existing adit (a horizontal shaft into a mine which is used for access or drainage). The force of the weight of a pool of waste in the mine overcame the strength of the adit, releasing the water into the environment. The EPA’s scope of work at Gold King Mine also included assessing the ongoing leaks from the mine to determine if the discharge could be diverted to retention ponds at the Red and Bonita sites.
The wastewater had been building up since the adit collapsed in 1995. There are networks and tunnels that allow water to easily flow between the estimated 22,000 mine sites in Colorado. As water flows through the sites it reacts with pyrite and oxygen to form sulfuric acid. When the water is not treated and it contacts (naturally occurring) minerals such as zinc, lead, cadmium, copper and aluminum and breaks down the heavy metals, leaving tailings. The mines involved in this incident were known to have been leaking waste for years. In the 90s, the EPA agreed to postpone adding the site to the Superfund National Priorities List (NPL), so long as progress was made to improve the water quality of the Animas River. Water quality improved until about 2005 at which point it was re-assessed. Again in 2008, the EPA postponed efforts to include this area on the NPL. From the available information, it’s unclear if this area and the waste pool would have been treated if the site was on the NPL.
In response, the “EPA is working closely with first responders and local and state officials to ensure the safety of citizens to water contaminated by the spill. ” Additionally, retention ponds have been built below the mine site to treat the water and continued sampling is taking place to monitor the water.
So how do we prevent this from happening again? Mitigation efforts to prevent the release were unsuccessful. This may have been because the amount of water contained in the mine was underestimated. Alternatively, if the amount of water in the mine was anticipated (and the risk more obvious) perhaps the excavation work could have been planned differently to mitigate the collapse of the tunnel. As a local resident, I’m especially curious to learn more facts about the specific incident (how and why it occurred) and how we are going to prevent this from recurring.
The EPA has additional information available (photos, sampling data, historic mine information) for reference: http://www2.epa.gov/goldkingmine