Why Nobody Can Walk Away From This California Mine

Iron Mountain Mine closed in 1963. The mountain never stopped draining. Nine miles northwest of Redding, California, a massive sulfide deposit — ninety-five percent pyrite — has been producing sulfuric acid for at least 780,000 years. A century of copper mining tore the mountain open, and now water sampled inside the abandoned Richmond Mine holds the record for the most acidic naturally occurring water ever measured on Earth: pH negative 3.6. The acid mine drainage killed millions of salmon in the Sacramento River, stripped over a hundred square miles of vegetation, and turned three creeks into dead channels. Listed as a Superfund site in 1983, Iron Mountain became the subject of a nearly $1 billion settlement — one of the largest in Superfund history. A lime neutralization plant built in 1994 must run in perpetuity. The estimated timeline for the pyrite to finish oxidizing: 3,200 years. Nobody can walk away from this place because the chemistry never stops. Sources: Nordstrom, D.K., Alpers, C.N., Ptacek, C., and Blowes, D. “Negative pH and Extremely Acidic Mine Waters from Iron Mountain, California.” Environmental Science & Technology, vol. 34, no. 2, 2000. Nordstrom, D.K. and Alpers, C.N. “Negative pH, Efflorescent Mineralogy, and Consequences for Environmental Restoration at the Iron Mountain Superfund Site, California.” Proceedings of the National Academy of Sciences, vol. 96, no. 7, March 1999. Alpers, C.N., Nordstrom, D.K., and Spitzley, J. “Extreme Acid Mine Drainage from a Pyritic Massive Sulfide Deposit: The Iron Mountain End-Member.” Environmental Aspects of Mine Wastes, Mineralogical Association of Canada, 2003. U.S. EPA, “Iron Mountain Mine Superfund Site: Cleanup Activities.” EPA Region 9, updated through current five-year reviews. U.S. Department of Justice, “U.S., California Announce Settlement to Clean Up One of the Country’s Most Toxic Waste Sites.” Press release, October 19, 2000. USGS California Water Science Center, “History of Iron Mountain” and “Environmental Effects of Mining Iron Mountain.” ca.water.usgs.gov/projects/iron_mountain.