The Zortman-Landusky mine was one of many heap leach mines located near the Fort Belknap Indian Reservation that was home to the Gros Ventre and Assiniboine Tribes. The heap leach process uses chemicals including cyanide to absorb the precious then re-separate them later. This specific mining operation had over a dozen cyanide spills including one incident that resulted in over 50,000 gallons of cyanide being spilled. The mine was also found to be leaking acids, arsenic and lead. This large and frequent contamination led to extensive surface and groundwater contamination. In 1993, the EPA filed a Clean Water Act suit that required a 32 million dollar clean up. Although the leaks happened in the 1980s, and the mine was eventually shut down in 1998, health problems on the reservation continue to be a problem. The company filed for bankruptcy and left the state of Montana without proper reclamation of the land including leaving toxins like arsenic, hills of waste rock and exposed mountain sides.
In 2000, the people of the Gros Ventre and Assiniboine Tribes sued the United States Bureau of Land Management for not protecting their rights or land from the heap leaching in the Zortman-Landusky mine. In 2005, Governor Brian Schweitzer signed a bill that guarantees 1.5 million per year to the clean up of the contaminated water resources through 2018.