Neither a mine operator nor its contractor was liable for a fire that had been set intentionally deep inside an Idaho underground silver mine, a judge has ruled.

Hecla Limited’s Lucky Friday Mine was evacuated without injury after an arsonist set blaze to a waste pile at the 4860 level in July 2011. However, MSHA’s investigation of the incident led to an order against Hecla and a citation against Cementation USA, Inc. The order and citation were written as “unwarrantable failure,” a designation reserved for alleged violations the agency believes constitute aggravated conduct beyond ordinary negligence.

For both enforcement actions, MSHA cited its standard at 57.4104(a) requiring that waste materials not be allowed to accumulate in quantities that could create a fire hazard. The agency proposed penalties of $38,000 against Hecla and $63,000 against Cementation.

Refusing to impose liability on Hecla or Cementation, Administrative Law Judge L. Zane Gill said the burden was on MSHA to prove, by a preponderance of the evidence, that a reasonably prudent person familiar with the mining industry and the protective purpose of the standard would have recognized what that standard was intended to prohibit.

Before the fire occurred, the waste pile primarily was made up of non-combustible scrap and rock and dirt had been barricaded to prevent access, first with a snow fence, then with a chain link fence. At the hearing, MSHA’s inspector noted that in some cases the agency allows some combustible material to be left underground and that an operator has discretion about how much to leave. He also conceded that the bulk of the waste material in the mine consisted of rock and dirt. However, he alleged that because wood was present, the debris presented a fire hazard.

Contractor personnel testified that kindling material had been removed for disposal on the surface and that the few remaining wooden materials were not easily combustible, a point the inspector also conceded. The inspector also testified he could find no evidence of an accumulation of combustibles because only a small amount of ash remained once the fire was extinguished. A fire official indicated no ignition source was present.

The agency argued that the Mine Act was a strict liability statute and that vicarious liability falls to an operator and its contractor even when unknown individuals enter a mine and violate the law. However, ALJ Gill disagreed, saying all the agency had been able to prove was that an arsonist set the fire. That alone is insufficient to prove a violation, Gill said in a September 30 decision vacating both enforcement actions.

“The Secretary cannot use vicarious liability or the Mine Act’s strict liability to infer that a criminal intervenor who intentionally set a fire in the gob pile in slot 4860 somehow violated Section 57.4104(a),” the judge said.