The Case of the Surface Miner Electrocution

The Case of the Surface Miner Electrocution

Multiple mistakes, including several Code violations, are uncovered in search for cause of dredge worker’s death

There was no question how the accident happened that day. On a cold winter afternoon in northwestern Ohio, a dredge operator was electrocuted when he tightened a chain clamp around an energized dredge power conductor while attempting to repair a pipe discharge leak. The victim's family, however, would demand answers to several unanswered questions in the lawsuit that followed the tragic incident — namely what specific circumstances had led up to the man's untimely death and who was at fault.

Called as defendants in the case, the victim's employer as well as the electrical contractor would undergo a thorough investigation. I was retained by the victim's family to determine the cause of the accident as well as offer recommendations for future prevention of similar incidents. Before putting the clues together in this case, it was important to recreate the scene, gathering as much detail as possible in order to understand the man's working conditions.

The environment

At the mine, a large 200-hp pump is used to pull sand and gravel from the bottom of a pond and pump it to shore for sizing and washing. The finished product is sold for use as construction aggregate and in the manufacture of concrete.

Operations are performed from a floating building or barge containing the pump equipment and controls. Floating pontoons are used to support the pipe, and electric power to the barge is supplied from a shore-based disconnect and breaker panel located ¼-mile away and fed by a pole-mounted, 3-phase, 440V corner-grounded delta transformer.

The piping and pontoons also serve as physical supports for the shore-supplied electric power (Photo 1). Leaks to the piping occur periodically, in particular, at junctions where the rigid steel pipe is joined through large, flexible rubber over-boots. The boots allow some wind and wave movement among the rigid pipe connections while also allowing some degree of barge freedom.

The accident

On the day of the incident, the dredge operator noticed water spraying out from behind the dredge and requested repair assistance from a coworker. The rubber boot had worked itself loose from the discharge pipe, allowing water to escape. A steel workboat was tied between the rear of the dredge and the first pontoon, and a hand-operated chain winch was connected to one end of the rubber boot. The other end was anchored to a support boom located on the dredge barge as a means of drawing together the boot and pipe.

After the chain clamp (Photos 2 and 3) failed to seat, the dredge operator applied penetrating oil and hit the handle with a pipe to get the chain's clamping teeth to seat into the chain links. Once the chain clamp finally seated, the dredge operator began to tighten the clamp. Shortly thereafter, the man's coworker noticed him shaking and making groaning noises.

Unable to free the dredge operator — assuming there was contact with a power line — the assistant panicked, jumping into the cold water and swimming to the first pontoon. Looking back, he saw arcing in several locations and realized that a power conductor was caught between the chain clamp and rubber line. After swimming to safety, the coworker reported that the dredge operator then fell to the floor of the boat and was unresponsive to his calls. Rescue personnel were unable to revive the dredge operator — whose death was ruled as an electrocution.

Background and investigation

The mine was classified as a non-metal, surface, sand and gravel mining activity, regulated by both the U.S. Department of Labor, Mine Safety and Health Administration and the State of Ohio, Department of Natural Resources. The electrical system at the facility, as well as its maintenance, repair, and operation, was required to comply with the requirements established by both federal and state regulatory mining authorities, and the worker safety laws promulgated by the U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), Title 29 Code of Federal Regulations, 29 CFR, §1910.5. OSHA addresses electrical safety in Subpart S, 29 CFR 1910.302 through 1910.399 of the General Industry Safety and Health Standards. The standards contain requirements that apply to all electrical installations and utilization equipment, regardless of when they were designed or installed.

After much investigation, I determined that the significant factors contributing to the miner's death were threefold: inadequate electric power cable clearance from the work space, operating practices that required employees to routinely work near electric power lines without proper training and protective equipment, and a chronically defective grounding system (Photo 4) that permitted a lethal quantity of ground-fault current to pass through the miner via the metal boat and pond water. More specifically, I concluded that the electrocution likely would not have occurred had the employer or the electrical subcontractor complied with any one of a number of safety requirements prescribed in regulation by the federal and state authorities and/or followed standard electrical installation and safety practices in the National Electric Code (NEC).

In addition, I found the electrical machinery and pipes at the facility were not grounded as required by law. The annual electrical ground safety inspections, also required by law, were intended to detect these and other electrical system safety deficiencies. However, despite several inspections and certifications by the electrical contractor, the grounding deficiency went undetected, and thus uncorrected.

In the overall scheme of things, system grounding deficiencies were only one of the many problems I found at the facility that contributed to the electrocution. Issues relating to noncompliance with federally mandated mine worker electrical hazard recognition and electrical safety training programs, deficiencies concerning the protection and placement of electrical equipment (Photos 5 and 6) and electric power cables, deficient electrical maintenance safety practices, non-compliance with state regulations governing qualified electrical personnel, and non-compliance with federal regulation governing personnel protective equipment, all created hazardous conditions at the facility. In fact, one state investigator described conditions at the mine following the accident as “danger of an imminent and extraordinary character.”

These additional deficiencies are consistent with the National Institute for Occupational Safety and Health (NIOSH) findings involving electrocutions in similar circumstances. According to NIOSH, any one of the five factors outlined in the FACE study (see “Electrocution Prevention Guidelines” on page 18) is sufficient to cause a worker fatality. However, in this case all five conditions were present!

  1. Established safe work procedures did not exist.

  2. Personal protection equipment was not provided or worn.

  3. Lockout/tagout procedures and policies were not established or enforced.

  4. The electrical system was found to have been in gross noncompliance with the provisions of OSHA, NEC, and NESC, as well as with the regulatory requirements of both MSHA and ODNR.

  5. Worker and supervisor training in electrical safety was nonexistent.

Lessons learned

In this case, I concluded that specific deficiencies led to the circumstances surrounding this accident, including:

Failure to properly ground the electrical system in accordance with regulation

a) Failure to ground metal parts likely to become energized.

b) Failure to provide an approved electrical connector for joining equipment grounding conductor.

c) Failure to provide an adequate grounding conductor.

Failure to perform requisite ground integrity tests as required by regulation per 30 CFR § 56.12028 to ensure proper functioning of ground safety system

  • Failure to protect electrical conductors from damage.

  • Failure to comply with regulatory requirements for electricians performing work on mine electrical systems.

  • Failure to provide initial and follow-up regulatory required mine electrical hazard training.

  • Failure to provide proper personnel protection equipment and protective equipment safety program as required in regulation.

Although they may not have directly contributed to the electrocution that day, several other deficiencies relating to contractor competence should have also raised red flags to any licensed electrician. For instance, a history of attempts to improve system power factor, switch out motor overload relays, repair failing motor contactors, change to a reduced-voltage “soft-start” motor controller, and the need to replace even the contactors on the soft-start motor controller shortly thereafter, is symptomatic of a deficient dredge motor power feed. Therefore, it should have motivated basic examination efforts. Other warning signs included the need for a fan in an undersized breaker/disconnect service enclosure and the extraordinary length of nearly one quarter of a mile of tray cable (Photo 7) that ran unprotected and submerged under water.

The outcome

A confidential settlement agreement was reached with the electrical contractor before the case was dismissed against the employer on a legal technicality. This decision stemmed from the fact that the miner was not technically an employee of the mine, but rather borrowed from a subsidiary business owned by the same employer.

Ruggieri is a forensic engineering industry expert and president of General Machine Corp., Washington, D.C.

SIDEBAR: Electrocution Prevention Guidelines

Excerpts from National Institute for Occupational Safety and Health (NIOSH) alerts, publications, and reports, including its “Fatality Assessment and Control Evaluation (FACE) Study,” help shed some light on the serious mistakes made in this case. According to NIOSH:

“Improperly installed or damaged equipment can be responsible for occupational electrocutions in a variety of ways. The most frequently cited OSHA electrical regulation is improper grounding of equipment or electrical circuitry. If the frame of a piece of electrical equipment or machinery does not have a grounding conductor attaching the frame to ground, as required to divert dangerous fault current to ground, and an electrical fault occurs, anyone touching that frame and any other object at ground potential would receive an electrical shock. Should a fault occur with a grounding conductor present, the circuit would open or trip as an alert that a problem existed …”

“Failure to maintain a continuous path to ground can expose entire electrical systems to damage and can expose the structures within which they are housed and workers within these structures to electrical and fire hazards.”

“The presence of moisture from environmental conditions, such as standing water, wet clothing, high humidity, or perspiration, increases the possibility of a low-voltage electrocution.”

“At least one of the following five factors was present in all 224 incidents evaluated by the FACE program:

  • Established safe work procedures were either not implemented or not followed;

  • Adequate or required personal protective equipment was not provided or worn;

  • Lockout/tagout procedures were either not implemented or not followed;

  • Compliance with existing OSHA, NEC, and NESC regulations were not implemented; and

  • Worker and supervisor training in electrical safety was not adequate.”

Most of the 224 occupational electrocution incidents investigated as part of the FACE program could have been prevented through compliance with existing OSHA, NEC, and NESC regulations and/or the use of adequate personal protective equipment (PPE).”

“All workers should receive hazard awareness training so that they will be able to identify existing and potential hazards present in their workplaces and relate the potential seriousness of the injuries associated with each hazard. Once these hazards are identified, employers should develop measures that would allow for their immediate control.”

SIDEBAR: Mine Electrocution Stats

An MSHA Electrical Hazard Alert bulletin furnished to all mine foremen and mine safety personnel identifies four frequently occurring hazardous conditions found in 56 mineworker electrocutions evaluated since 1985. The MSHA Hazard Alert Bulletin breaks down the casualties and identifies which one of the four conditions outlined below were responsible for the electrocutions in each casualty case.

  • Failure to lockout electrical power prior to performing maintenance;

  • Failure to isolate electrical power lines;

  • Inadequate grounding of electrical equipment; and

  • The special hazards of electricity in a wet environment.

In this particular case, the presence of all four of the above hazardous conditions were found as well as additional training deficiencies not named in the MSHA Bulletin.

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