Physical Safety Hazards
An AML site is an area of unreclaimed abandoned mining and/or exploration. An AML feature is an unreclaimed structure or surface expression of mining or exploration within a site (such as a shaft, adit or pit).
To date, over 14,000 AML features have been inventoried and entered into BLM's National database AMSCM. Inventories have focused primarily near population centers and areas of high public use. Highest priority for closure of hazardous features area sites where a death or injury has occurred and locations within or in proximity to developed recreation sites.
An open shaft is a vertical opening that may be hundreds of feet deep. A shaft may be visible or it may be hidden by debris or vegetation. Commonly, unstable slopes lead up to the adit opening. Ladders or ropes, which are usually rotten or broken, often remain in the shaft, tempting entry. Adits (horizontal entryways) offer a variety of dangers including unstable rock ceilings and walls and decayed rock-support structures that may give way, causing a rock fall. Shafts and adits provide entry into underground workings that may include drifts (horizontal excavations) and winzes (openings on the floor that extend to a lower mining level and are often hidden by lumber or debris that can give way when stepped on).
Abandoned mines may have pockets of carbon dioxide or other deadly gases that displace oxygen. Within a short distance of an entrance there is total blackness. A person could easily become disoriented and lost, even with a flashlight. With a failed light source, the chances of getting out of an extensive mine, honeycombed with miles of workings, in absolute darkness, are remote. Snakes and bat droppings, explosives, and toxic chemicals pose additional hazards to human intruders.
Surface features include open pits and highwalls that are prone to collapse and unstable ground that if walked on could open into a shaft or open stope (mined-out area). Old buildings & equipment are prone to collapse if crawled on or entered.
Water seeping through or out of mine workings, tailings, or mine waste rock may leach out chemicals and metals. This runoff, called acid rock drainage can adversely affect soil and water quality posing a hazard to vegetation, wildlife, and human health. Ground and surface runoff collecting in the bottom of a pit poses a similar hazard. Chemicals stored on site in containers may deteriorate and leak into the environment, affecting vegetation, wildlife, and human health. Mined-out areas may cause excessive erosion and flooding as well as silting of streams, adversely affecting fish and riparian habitats.