The Chevron Questa Mine sits in Taos County, New Mexico, covering about 3 square miles of former mine and mill land plus roughly 1.5 square miles of tailing impoundments. The mine produced molybdenum intermittently from 1920 until it closed permanently in 2014. EPA added the site to the National Priorities List (NPL) in September 2011. During its operating life, the mine deposited about 328 million tons of acid-generating waste rock across nine large piles, contaminating soil, sediment, surface water, and groundwater.
Contaminants at the site include a long list of metals: aluminum, antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, iron, lead, manganese, molybdenum, nickel, uranium, vanadium, and zinc. Other substances found include aroclors (types 1248, 1254, and 1260), fluoride, nitrate, sulfate, and total dissolved solids. These contaminants are present in groundwater, surface water, sediment, soil, leachate, and solid waste.
Chevron Mining Inc. is the responsible party conducting cleanup under EPA oversight. A Record of Decision issued in December 2010 called for excavation and off-site disposal of contaminated soil, removal and regrading of waste rock piles, installation of covers and revegetation, groundwater extraction and water treatment systems, and removal of molybdenum-contaminated soil and tailing spill deposits. Removal actions began in 2012 and included excavating PCB-contaminated soil, removing tailing spill deposits along the Red River, and clearing sediment from Eagle Rock Lake. A May 2017 settlement agreement required Chevron Mining Inc. to build a tailing facility cover over roughly 275 acres, install mine dewatering and groundwater extraction systems, build a new water treatment plant, and upgrade seepage barrier systems. In September 2023, a Fourth Amendment to that settlement added five more early design actions covering water treatment residuals management, historic buried tailings, dam infrastructure, remaining waste rock piles, and updated groundwater characterization.
EPA has determined that human exposure is under control across the site and that groundwater migration is stabilized with no unacceptable discharge to surface water. However, physical construction is not yet complete, and the site has not been deleted from the NPL. A five-year review was completed in August 2022, with the next one estimated between August and October 2027. Remedial design work is ongoing through an estimated 2028.
Community members can get involved through several EPA programs. These include the Technical Assistance Needs Assessment Tool, the Technical Assistance Services for Communities Program (which provides free expert review), the Partners in Technical Assistance Program through colleges and universities, and Technical Assistance Grants for nonprofit groups to hire independent advisors. Grant recipients must contribute a 20 percent match, typically through volunteer hours. Site records are available for public review at the Village of Questa Municipal Offices at 2500 Old State Road 3, Questa, NM, or by calling (505) 586-0694.
