Accepting estimates of electrical output from a welding machine from experts representing MSHA and a mine operator, an MSHA judge nevertheless turned to reference literature to determine if contact with that current was likely to produce a serious injury.

Administrative Law Judge Priscilla Rae upheld a violation of MSHA’s electrical standard against River View Coal, LLC at its mine of the same name in Kentucky. The citation was written in August 2012, after an inspector observed bare wires on the electrode holder of a welder mounted on a two-person diesel-powered mantrip. A mantrip is a shuttle for transporting miners underground, and an electrode holder is an insulated clamp that holds the welding rod in place during welding.

In court, MSHA’s expert witness and counsel for River View jointly calculated the current a miner would experience if he or she touched the bare electrode. That calculation, coupled with another offered by River View’s expert, led both sides to agree the range of the current would be between 28 and 35 milliamperes (mA).

However, they could not agree on the impact that current would have on the human body. MSHA asserted the shock could affect the heart and/or produce an injury from a miner's involuntary reaction to being shocked. That conclusion had led the agency to classify the violation as significant and substantial (S&S), i.e., one likely to produce serious injury. Conversely, the operator asserted a miner would feel only a tingle.

Both parties submitted reference materials. Faced with the conflicting testimony, ALJ Rae turned to those materials for guidance. She noted that 300-500 mA would be needed to affect the heart. In addition, the so-called let-go threshold whereby the flexors of the arm contract but still allow release of the hand from a shock hazard is 75 mA for a 154-pound male. Since the estimated 28-35 mA current fell significantly below either the let-go or heart-damaging level, Rae determined that serious injury was unlikely and cut the S&S classification to non-S&S.

MSHA also had written the ticket as representing moderate negligence, but Rae said the operator’s safety requirements and diligence in conducting weekly examinations of electrical equipment justified only a finding of a low level of negligence. As a result, she cut MSHA’s $687 fine to $125 in a decision released in July.