The road to zero: The 50‑year effort to eliminate roof fall fatalities from US underground coal mines

Sixty years ago, underground coal mining was the most hazardous job in the United States. Roof falls killed about 100 miners every year, more than all other causes put together. Fast forward half a century to 2016, and the first year ever with zero roof fall fatalities. Just three miners were killed by roof falls during the following six years. To understand how this historic goal was achieved, this study analyzed hundreds of roof fall fatality reports covering five decades. It found that the immediate effect of the Federal Coal Mine Health and Safety Act of 1969 (Coal Act) was to reduce the riskiest activities, like needlessly going under unsupported roof. Other hazards, like large roof falls, required technological developments before they were brought under control. Roof control plans, which the U.S. Bureau of Mines had been advocating since the 1920s, fostered the necessary improvements in both the safety culture and the mining technology. Background In 1968 underground coal miners worked in the most dangerous industry in the United States. Statistically, being a coal miner was almost as dangerous as being in uniform at the height of the Vietnam War. And coal mining’s safety record had hardly improved in decades, in marked contrast to other dangerous industries like steel or railroads. Roof falls were the greatest single hazard underground, responsible for about as many deaths as all other causes combined. Fig. 1 Roof fall fatality rates for large underground coal mines by fundamental cause. Fig. 2 Roof fall fatality rates in large underground coal mines attributable to different types of inadequate safety technology. Methodology To determine what factors were behind the high death rate, this study analyzed all the USBM roof fall fatality reports from 1968. It found that, even at large mines, more than half of the roof fall fatalities that year were the direct result of an inadequate safety culture. These deaths were due to blatantly ignoring “well-known, basic principles” of roof control, such as not going under unsupported roof. The remainder of the fatalities could be attributed to inadequate safety technology, which fell into four subcategories: Work processes that required miners to go inby the roof supports.Failures of the roof support system that resulted in large roof collapses.Loose rock falling from between supports.Special projects, including underground construction and rehabilitation of roof falls. Effect of the Coal Act Just eight years later, after the Farmington Mine Disaster and the passage of the 1969 Coal Act, a coal miner’s chances of being killed by a roof fall had been reduced by two-thirds. But even that statistic underestimates the change in the safety culture. The analysis of the fatality reports from 1975 to 1976 found an 80 percent drop in blatant violations of safety rules (Fig. 1). It also found that the rate of roof fall fatalities attributable to inadequate technology fell by more than 50 percent during the same eight-year period, even though few new roof control technologies came into wide use during that time. Instead it seems that mine operators intensified their use of existing technologies. For example, the study found data showing that the density of roof bolting increased by at least 40 percent industry-wide in the five years after Farmington. Technological developments The remainder of the study homed in on those technological developments that ultimately led to zero. In the 1970s some work processes still required miners to go inby the roof supports. The installation of automated temporary roof support (ATRS) on roof bolting machines, which ended the need to set temporary supports manually, had the greatest effect. By the late 1980s this category of roof fall fatalities had been largely eliminated (Fig. 2). Major roof falls were the next target. Cable bolts expanded the ability of roof bolting systems to manage difficult ground that required longer supports. Cable bolts also improved safety during pillar recovery, together with better mining practices and Mobile Roof Supports. The analysis showed that these technologies helped to substantially reduce fatalities from major roof falls during the first decade of the 2000s. A number of incremental improvements ultimately proved sufficient to reduce the hazards from the last two significant sources of roof fall fatalities, loose rock and special projects. Conclusions Today, underground coal mining no longer stands out as an “inherently dangerous” profession. The Coal Act foresaw how this could be accomplished through a gradual process of cultural change and technological improvement. It stated that “each operator shall undertake to carry out on a continuing basis a program to improve the roof control system of each coal mine and the means and measures to accomplish such system.” Roof control plans played a central part throughout, helping to implement new technologies as they were developed on a mine-by-mine basis. References A list of all references is available in the full paper.

The road to zero: The 50‑year effort to eliminate roof fall fatalities from US underground coal mines

Authored by:
Christopher Mark

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To view this article you must be a member of SME/UCA.

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