the Secretary’s authority to grant a mine-specific modification under section 101(c) which is at issue in this case.
On July 29,1982, Emerald filed a petition with the Secretary seeking modification of the safety standard set forth at 30 C.F.R. § 75.3262 at its No. 1 Mine.3 The standard is one of several mandatory safety standards governing mine ventilation. Underground coal mines are ventilated by a set of tunnels or “entries” which continuously move air throughout the mine. At the Emerald No. 1 Mine, the “intake escape-way” is the entry through which fresh air is brought into the mine. It is also the miners’ means of escape in the event of an emergency. Air already used to ventilate the mine is removed through the “return entry.” The “track entry” is the entry through which miners and materials are hauled in and out of the mine. Finally, the “belt entry” is the tunnel containing the conveyor belts which transport coal from the active working sections of the mine to the surface.
The standard sought to be modified limits the velocity of air permitted in belt entries and prohibits the use of belt entry air to ventilate the underground working areas of the mine.4 By limiting the air velocity in belt entries, the standard helps prevent the fanning of fires that may originate along belt haulageways. In addition, by prohibiting the use of air to ventilate working places, the standard keeps belt entry contaminants such as coal dust or fire by-products from reaching miners.
In its petition, Emerald proposed to use belt entry air to supplement the ventilation of the active working places of the mine. As an alternative to the protection afforded by the standard, Emerald planned to install a low-level carbon monoxide (CO) detection system in the belt entries. According to Emerald, the CO detection system would provide miners with early warning of a fire in the belt entry before the fire reached a stage where the products of combustion would present a hazard to miners. Because the miners would be alerted in time for them to exit the mine safely, Emerald argued that the proposed modification would provide a measure of protection equal to that of 30 C.F.R. § 75.326.
Following the filing of the petition, MSHA conducted a field investigation pursuant to 30 C.F.R. § 44.13. On June 24, 1983, the Administrator for Coal Mine Safety and Health issued a proposed decision granting Emerald’s petition subject to stated conditions. Thereafter, UMWA exercised its right under 30 C.F.R. § 44.14 to request a hearing before a Department of Labor Administrative Law Judge (AU) concerning the proposed decision. After the hearing, at which Emerald, MSHA and UMWA participated, the AU denied the petition on the ground that Emerald had failed to establish that the proposed alternative would meet the requirements of section 101(c).
Emerald and MSHA subsequently appealed the AU’s decision to the Assistant Secretary of Labor, as is permitted under 30 C.F.R. § 44.33. On October 3,1985, the Assistant Secretary reversed the AU’s decision and granted the petition, subject to certain conditions.5 In determining whether the modification should be granted under section 101(c), the Assistant Secretary
2
The standard is also set forth at 30 U.S.C. § 863(y)(l).
3
The Emerald No. 1 Mine is an underground bituminous coal mine that was opened in 1977 in Greene County, Pennsylvania.
4
The standard provides in relevant part: 30 C.F.R. § 75.326.
5
The Assistant Secretary’s decision constitutes the final decision of the Department of Labor. 30 C.F.R. § 44.51.