The common belief prior to the spring of 1972 was that the risk of fire was not a concern in underground hardrock mining. Miners worked in tunnels of stone that they, themselves carved. Unlike their counterparts in coal mines where fire hazards are a serious concern, hardrock miners reassured themselves that "rock doesn't burn". Accordingly, their precautions, planning, training and equipment to respond to fires were not a priority. The risk of fire was summarily dismissed behind the rationale that "It can't happen to us."
On May 2, 1972, a fire broke out in the old workings of Idaho's Sunshine silver mine burning support timbers, ventilation stoppings and polyurethane insulation. The fuel-rich fire smoldered, producing toxic smoke and depleting oxygen levels. As the fire compromised the ventilation stoppings, air flow was short circuited causing smoke to be forced into the working areas of the mine by the very fans that were designed to force the bad air out.
In less than two hours, 91 of the 172 miners underground died as a result of carbon monoxide poisoning.
The tragedy not only had a lasting effect on the families and the community it impacted, but the industry as a whole also changed significantly. The Mine Safety and Health Act of 1977 was seen as a direct result of the Sunshine mine fire. This landmark legislation implemented strict enforcement powers that the Mine Act of 1968 did not. More importantly, it included metal and non-metal mines such as Sunshine into its provisions.
A study of the events leading up to the Sunshine mine disaster reveals a host of opportunities where a comprehensive risk assessment and emergency response plan could have benefited the evacuation efforts and surely saved lives. Moreover, it offers an example of how cavalier attitudes and unfounded beliefs that "it can't happen to me" can be devastating to safety initiatives.
Located in the Coeur d'Alene district in Idaho, the Sunshine silver mine was the largest and richest in the United States. In its 120 years in operation, the mine produced over 360,000,000 ounces of silver, which dwarfed all of its competitors.
The Sunshine was a deep shaft mine that cored more than 5,800 feet vertically into the mountainside with horizontal lifts following silver deposits. The lifts were accessed through a central elevator shaft and were identified by numbers representing their depths below the portal. For example, the 4400 lift was 4,400 feet down and ran horizontally away from the central shaft.
Prior to the fire, the mine had a work force of around 522 miners, 429 of whom worked underground. The vast majority worked as "gyppo miners" (a slang term for miners whose pay is based primarily on how much ore he extracts). The workforce resulting from this structure was not only fiercely independent, but also was highly motivated to stay in the mine as long as possible to uncover as much silver as they could.