Seventeen people died in abandoned mines in the United States in 1999. In Wyoming, hunters, hikers, cave explorers and other recreationists who use public and private lands are at risk of death or serious injury. The Abandoned Mine Land Program (AML) has cataloged many abandoned mine sites in Wyoming. However, many more sites exist in remote areas, or on private land. Anyone who observes an abandoned mine is encouraged to report the site to AML at 307-777-6145. Exact location and access routes will be especially helpful. IF YOU ENCOUNTER AN ABANDONED MINE, DO NOT ATTEMPT TO ENTER! Many of the dangers posed by these sites are not readily seen, or cannot be seen at all.

Horizontal openings: The mine opening (known as a portal or adit) may seem stable, but rotting timbers and unstable rock formations make cave-ins a real danger. The darkness and debris in old mines make identification of the hazards difficult.

Vertical shafts: These can be hundreds of feet deep. At the surface, openings can be hidden by vegetation or covered by rotting boards or timbers. Inside old mines, shafts can be camouflaged by debris, or hidden by darkness in the mine.

Explosives and toxic chemicals: Blasting caps, dynamite, and chemicals were often left behind when the workings were abandoned. Explosives become unstable with age, and can be detonated by the vibration of footsteps. Abandoned chemicals such as cyanide, arsenic, mercury and other deadly toxins may be present in leaking and deteriorating containers.

Dangerous gases: Lethal concentrations of methane, carbon monoxide, carbon dioxide and hydrogen sulfide (to name a few) may accumulate in underground passages. Oxygen deficient air may cause suffocation. People have died within a few feet of the mine openings.

Water: Impounded water may be highly alkaline or acidic (resulting in skin burns), as well as deep and cold (contributing to hypothermia).

Spoils (rock and dirt) piles: These loose piles can collapse or slide, burying an unsuspecting victim.

Equipment and buildings: Abandoned surface structures and old mine equipment may collapse on bystanders.

Highwalls: These are the excavated vertical cliffs in surface pits and quarries. They can be unstable and prone to collapse. Highwalls may not be visible from the top, presenting a danger to off road drivers.

Radon: Radon is a natural radioactive decay product, and is known to be a factor in some lung cancers. Radon can accumulate in high concentrations in poorly ventilated mines.

Wildlife: Rattlesnakes, bears, mountain lions and other wildlife frequent old mine sites.

Disorientation: There is no natural light inside of mine workings. Many workings meandered randomly as miners followed an ore vein. It is easy to become lost and disoriented in a maze of mine workings, especially if lighting equipment fails.

Mine Fires Areas: Mine fires create surface hazards in abandoned coal mine areas. As fires burn within the seam, fissures can open to the surface delivering deadly gases into the atmosphere. The area around the fissure may not be capable of supporting the weight of a human or vehicle, and may collapse into the burning coal or the mine void.