OSH alert – Cable strike electric shock (March 2015)

Key learnings from a High Potential Incident.

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HPI OSH Alert #466

Date of incident: 25/03/2015

Safety Flash issued: 26/03/2015

466cableWhat happened?

While trenching, a Water Corporation contractor struck a low voltage cable which was located in a loop approximately two metres from the base of a power pole. A nearby resident received an electric shock through a handheld showerhead around the same time. The resident was cleared by medical staff shortly after the incident.

Why did this happen?

  • Error in the reading of Dial Before You Dig (DBYD) Plans – the cable location sub-contractor and main contractor failed to notice the looped cable marked on the plans.
  • Presence of nearby Telstra cable caused electromagnetic interference, resulting in false readings on the cable locating device – unknown limitation of the cable locating device.
  • Looped cable not installed in accordance with Western Power specifications, including alignment, warning tape or slabs and sand backfill material.
  • Failure to positively locate by potholing the excess looped low voltage cable transitioning from the power pole into the ground surrounding the power pole.

What will our organisation do to stop this from happening again?

  • The Water Corporation will review and assess the contractor’s findings of a technical review into the limitations of EMF detection devices, and communicate the results as appropriate.
  • Raise awareness, via this OSH Alert, that there is potential to misinterpret small scale hard copy DBYD plans, and it is recommended to enlarge the plans for clarity on the detail contained within them.


What key learnings can you discuss with your team to stop this from happening again?

  • Dial Before You Dig (DBYD) Plans can be difficult to read, and larger hard copy plans or electronic plans with an ability to zoom into detail should be considered for use on site
    • Does our team need to use DBYD plans for either planning or undertaking works?
    • If we use DBYD plans, how can we make sure these plans are available on site and provided in a format that makes details easy to read?
    • Do our team members who use DBYD Plans know what to look for, and how to correctly interpret the plans? 
    • Are they appropriately instructed in how to interpret One Call Plans?
  • Buried electrical cables and cable loops must be physically located prior to mechanical excavation
    • Is our team relying too much on DBYD Plans and Cable Avoidance Tools to determine where we think the services are, without the potholing to prove the location of services in and adjacent to the digzone?
    • How do we reinforce and ensure that our team members comply with existing Safety Essentials for High Risk Activities? What happens when this is not practical?

Further information

If you would like further information about anything included in this HPI OSH Alert, please contact Charis Neumann, Senior OSH Analyst Incident Management on (08) 6330 6629.

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