Exploration drill rig contacts overhead powerline

Background

An air core exploration drill rig was being set up to drill a hole located within a farmer's paddock. The operator had lowered the stabilising jack legs and was in the process of raising the mast when the winching cable contacted a 12.7kV Single-Wire Earth Return (SWER) overhead powerline. The SWER line was approximately 7m above ground level. The drill operator received a shock and immediately retreated from the rig at which point the overhead line was observed. Re-exposing themself to the electrical hazard, the operator approached the rig and activated the rig’s hydraulic levers with a 'shovel' to lower the mast.

The operator was taken to hospital for observation and later released uninjured.

The SWER powerline and associated infrastructure was not marked on locality maps provided by asset owners or within government authority databases. The line's power poles were several hundred metres away and were not readily visible from the incident location.

Extreme caution should be taken after contacting SWER powerlines, as they may automatically re-energise up to three times before remaining permanently 'tripped out'.

Recommended ways to control risks

To reduce the risk of contact with electrical energy, mine and exploration operators should:

• Identify all potential hazards during risk assessments and assess the adequacy and benefits of existing control measures.
• Consider additional control measures, such as:
  • Implement (eg retrofit) protective indication alarms to detect overhead high voltage electricity sources coupled with optional motion-stop technology.
  • Introduce secondary levels (eg supervisors and/or managers) of pre-task inspection and oversight to improve the capacity to identify and recognise potential hazards.
  • Marking overhead powerlines in accordance with Australia Standard AS 3891-2 as a visual warning.
• Include a broad range of expertise and personnel when developing risk assessment teams to ensure all aspects of risk are considered.
• Ensure employees are adequately and regularly trained in identifying hazards and assessing risk.
• Ensure employees are adequately and regularly trained in the measures used for managing and controlling risk associated with electrical energy (eg electrically energised plant should be isolated/barricaded, and employee access/contact prevented).
• Ensure employees are aware electrically energised plant can only be accessed by qualified and certified electrical professionals (eg authorised power distributors).

Legal duties

Under the Occupational Health and Safety Regulations 2017 (OHS Regulations), mine operators must:

• identify all mining hazards at their mine and assess associated risks, so far as is reasonably practicable
• implement risk controls that eliminate or reduce risks, so far as is reasonably practicable
• review and, as necessary, revise the identification of hazards, assessment of risks and risk control measures at least every three years, as well as:
  • before any mine modification is made
  • after any incident involving a mining hazard occurs at the mine
  • if a health surveillance report identifies detrimental effects to a person and in response that person is removed from work or assigned to alternative work, or
  • after receiving a request from a health and safety representative (HSR)
• for prescribed mines there are also obligations to establish, implement and maintain a safety management system.