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Statement of Need: The use of diesel-powered equipment is increasing steadily in underground coal mines across the United States, from 175 units in 30 mines in 1977 to more than 2,885 units in 170 mines in 1995. Given the current state of the industry and assuming no change in existing regulations, MSHA projects that the presence of diesel equipment in the industry would increase to about 3,520 units in 250 underground coal mines by the year 2000. ^PCurrently, MSHA regulations do not specifically regulate this type of equipment, in contrast to other more conventional mining equipment. Diesel equipment in underground coal mines poses a risk of fire or explosion, as a result of the introduction of an ignition source (the diesel engine) into an environment that may contain methane gas. Poor fuel handling and fuel transfer procedures underground present significant fire hazards. Between 1979 and 1992, MSHA investigated 10 diesel-equipment-related fires in underground coal mines. Because of the methane gas and coal dust present in the underground coal mining environment, any fire presents a significant risk of loss of life. Without rules for the design, use, and maintenance of diesel-powered equipment, the Agency also lacks an effective means to regulate health and safety hazards associated with diesel equipment. ^PUnder current regulations, diesel-powered equipment is not required to have a number of important safety features that have long been required on electric equipment, such as cabs and canopies (which protect equipment operators from roof falls), automatic emergency parking brakes, and methane monitors, which shut equipment off when methane concentrations reach certain levels. ^PIn July 1988, a Federal advisory committee convened by the Secretary of Labor made recommendations to the Secretary concerning safety and health standards for the use of diesel-powered equipment in underground coal mines. Based on those recommendations, in 1989 MSHA published a proposed rule that: included criteria for the approval of diesel engines and other related equipment; addressed exposure limits, monitoring, and recordkeeping requirements for certain diesel emissions; and provided corresponding safety standards for the use of diesel-powered equipment in underground coal mines, including the safe storage and transport of diesel fuel and the training of mechanics. MSHA is working on a final rule which will provide increased protection for miners, allow for flexibility in control technology, and minimize recordkeeping requirements.

Alternatives: On January 6, 1992, MSHA published an advance notice of proposed rulemaking soliciting comments on the potential health effects from occupational exposure to diesel exhaust particulates, especially in the closed environment of the underground mine. MSHA has decided to continue to address the potential health effects from exposure to diesel particulates in a separate rulemaking. ^PMSHA considered third-party testing and certification of the results as an alternative to MSHA testing for the approval of diesel-powered equipment. The final rule may contain a combination of approaches to address this issue.

Anticipated Costs and Benefits: The scope and nature of the final rule is currently under development and, thus, final estimates of costs and benefits have not been determined. MSHA had made a preliminary assessment in 1989 that the proposed rule would have had an incremental annual impact of over $20 million on the mining industry. Subsequent estimates, however, project the incremental annual cost to be from $16 million to $35 million, depending upon the alternatives selected. ^PMSHA projects that one benefit of implementing this regulatory protection will be a reduction in the risk of fires and explosions, and corresponding injuries, resulting from the use of diesel-powered equipment in underground gassy mines, as well as a reduction in the incidence of potential adverse health effects that result from exposure to diesel exhaust. ^PThe final rule also will encourage the use of advanced diesel technology, such as flame arresters, spark arresters, water scrubbers, and exhaust filters in the approval of diesel engine design, all of which would improve the safety and health of miners. Also, because some hazards are currently addressed in the mine ventilation plan, the final rule will reduce the resources and paperwork associated with the submission and approval of this aspect of the ventilation plan. It also will provide for more uniform requirements, resulting in more consistent enforcement.

Risks: The use of diesel-powered equipment in underground coal mines poses a risk of fire or explosion by introducing an ignition source through the engine itself and from the underground handling and storage of diesel fuel. Without rules for the design, use, and maintenance of diesel-powered equipment, the Agency lacks an effective means to control safety and health hazards associated with diesel-powered equipment in the confined environment of the underground coal mine.