-mine property can work from a practical standpoint, given the various requirements of the Mine Act for mine operators and MSHA.BackgroundThese are the essential facts: KC Transport is an independent trucking company that operates off-road haul trucks at nearby mines and over-the-road trucks unrelated to mining. KC Transport performs approximately 60 percent of the services from its parking and maintenance facility for a nearby coal operator. Further, no mine operator employs personnel or maintains equipment at the facility. A logging company also utilizes the facility. The case began when an MSHA inspector visited the KC Transport facility looking for trucks he had cited at the nearby mine—in order to confirm abatement and terminate those citations. While at the KC Transport facility, the inspector observed two mine trucks being repaired while not blocked against motion. The inspector subsequently issued two citations to KC Transport.The language at the heart of this case is found in 30 U.S.C. § 802(h)(1)(C). This section defines a “coal or other mine,” in pertinent part, as “facilities, equipment, machines, tools … used in, or to be used in, or resulting from, the work of extracting … minerals.” (Emphasis added.) MSHA argued throughout the litigation that this language was unambiguous and clearly applicable to the mining trucks at the trucking facility. Only later, when confronted by the circuit court’s indication that it viewed the language as ambiguous, did the secretary offer a last-minute interpretation. The secretary’s new, very general interpretation simply required MSHA to determine if equipment constituted a mine by conducting a “fact-based inquiry” to evaluate how closely related the relevant facility or equipment was to mining activity. In this evaluation, according to MSHA, location is “but one factor that may be relevant to this ‘use-in-mining’ analysis.” (Emphasis in the original.)The D.C. Circuit’s AnalysisThe circuit court did not see MSHA’s interpretation as workable. It