At 11.05am on 1 June 2023, Wellington Electricity’s network protection system cut part of its power supply for safety reasons, causing an outage to 772 homes and businesses across Porirua City.
The cause: a cable strike. A fault crew attended to find a jackhammer driven through a live, high voltage electricity cable. They immediately made the site safe and had power remotely re-routed and restored in less than an hour, resulting in minimal customer impact.
Sadly, the same cannot be said for the jackhammer operator. They were taken to hospital with facial burns caused by the 11,000 volt electrical flashover that surged through the air as the cable was hit.
This could have been avoided. It was found that no mark out had been obtained by the third-party civil contractor – a critical step in locating underground services. As a result, they may be subject to fines or even prosecution, as well as being held liable for any costs incurred.
The events of that day serve as a stark reminder of how a seemingly routine excavation can end with a potentially catastrophic outcome if safe digging practices are neglected. In 2022 alone, Wellington Electricity saw its underground cables struck once a week, on average.
Remember – to keep yourself and others safe, ALWAYS follow the five rules of safe excavation:
Plan ahead by lodging your beforeUdig enquiry at least two full business days before starting any excavation to ensure you have the correct information and safety measures in place.
Prepare by reviewing the utility plans. Contact the utility if you need assistance. Look for clues onsite such as pit lids, marker posts and meters. Engage a qualified locator which includes undertaking electronic location and marking out prior to potholing.
To establish the exact location of all underground utilities, pothole if permitted using the asset owner’s stated method as specified on the asset owner’s plan and / or information pack - typically, a slit trench, hand dug using a non-conductive shovel.
If potholing has occurred, protect the infrastructure by using various methods, such as communicating to all working on site, erecting barriers and / or marking the location of the exposed infrastructure.
You should only proceed with your excavation work after you have planned, potholed (unless prohibited) and have protective measures in place.