The Bonita Peak Mining District sits in San Juan County, Colorado. It covers 48 historic mines and mining-related sources that have released heavy metals into soil, groundwater, and surface water. Contaminated water and sediment flow directly into Mineral Creek, Cement Creek, and the Upper Animas River, with some metals reaching the Animas River itself.
State and federal agencies first assessed the area in the 1990s. They found severe damage to aquatic life from both naturally occurring and mining-related heavy metals. Water quality in the Animas River improved through 2005 but declined after that. A discharge event at the Gold King Mine in August 2015 prompted EPA to propose the site for the Superfund National Priorities List in April 2016. It was officially listed on September 9, 2016.
EPA has taken several cleanup steps. A 2019 Interim Record of Decision covered 23 source-area mines. Work at those mines ran from late 2019 through the 2025 field season and focused on stabilizing waste areas and diverting runoff away from mine waste. That interim remedy was completed as of March 31, 2026. A separate 2021 Interim Record of Decision addressed building a sitewide repository for mine waste. The Interim Water Treatment Plant at Gladstone continues to treat acid mine drainage, which is water that turns acidic after contacting exposed mine materials, from the Gold King Mine.
EPA completed a Five-Year Review in October 2024. It concluded that the remedy will protect human health and the environment once all cleanup actions are finished. The next five-year review is scheduled for Fall 2029. The site is still in an active phase, with long-term decisions about full site cleanup ahead.
Community members who want to stay involved can follow EPA's updates on the Bonita Peak Mining District through official EPA Superfund site communications. Five-year reviews are public documents and offer a regular checkpoint for tracking cleanup progress.
