​            To better understand how the Gold King Mine spill happened, we must look at the work that was being done in the area prior to the spill. After large-scale mining in the Silverton area closed in 1991, the State of Colorado’s Water Quality Control Division (CWQCD) began a new program to establish new standards for water quality in the upper Animas River watershed. This program involved the installation of hydraulic bulkheads to slow seepage from mine entrances, as well as settling ponds and treatment plants to raise the pH of the water with the addition of calcium carbonate or lime (Clark 2021). Despite these new efforts, the Gold King Mine was not included in this program since other areas received priority. As a result, the water quality of Cement Creek and the waters directly below it began to worsen over the years that followed. Bulkheads were installed on some entrances, but didn’t do much in slowing the slow discharge of metal-laden water from the Gold King Mine. “By 2006, peak discharges from GKM had risen to over 300gpm. Three years later, the GKM was found to be releasing nearly 200,000 pounds of metals into the watershed each year” (Clark 2021). In 2010, significant declines in trout populations were recorded in the area, which got the attention of the United States Environmental Protection Agency (EPA), prompting them to consider Superfund designation for the area. At one point, the Sunnyside Gold Corporation (the owner of the land at the time) made an offer of $10 million to fund the construction of a water treatment facility on Cement Creek, in exchange for being exempt of potential liabilities for the restoration of the area going forward. Nothing ever came of this offer until the spill in 2015. In 2014, the Colorado Division of Reclamation, Mining, and Safety (CDRMS) requested of the EPA for the reopening and stabilization of the Gold King Mine’s level 7 adit, which had previously collapsed. After some surface-level work in the area in 2014, a crew consisting of EPA contractors and one CDRMS official returned to the site in 2025 to continue excavation on the level 7 adit. As the crew was excavating the area on August 5, 2015, an EPA contractor miscalculated the depth and pressure of the water behind a bulkhead, creating a breach in the mine entrance. The team quickly stopped what they were doing, but it was already too late. “Within minutes, a portion of bedrock fell away from the mine’s opening and a greater volume shot upward 1.5-2 feet; the breached opening later measured 10 feet in width and 15 feet high” (Clark 2021). It wasn’t long before the water released reached its way into Cement Creek and the Animas River, creating the event we now refer to as the Gold King Mine spill.​