Working safely near underground assets
Damage to underground assets (such as electric cables, gas, water and sewerage pipes) caused by excavation work can result in serious or potentially fatal incidents including burns, electric shock and gas releases or explosions as well as disruption of the electricity, gas or water supply.
Injuries can be caused by the explosive effects of arcing current. When a live cable or gas pipe is cut or crushed by an excavator bucket or penetrated by the point of a tool it can cause hazardous fires or explosions.
Incidents may also arise when damage to these assets is unreported and not repaired.
Before starting any excavation work all underground assets must be located. The following will assist with this process:
- Dial Before You Dig
- site plans
- cable or pipe detection
- carefully executed pilot or test holes.
Dial Before You Dig and site plans
Dial Before You Dig is a free national community service that provides information about the location of underground pipes and cables belonging to the various utility companies around Australia such as SA Power Networks, ElectraNet or Australian Gas Networks.
Dial Before You Dig alone may not identify all underground pipes or cables. Some may be part of a private installation and some of Australia's underground asset owners are not members of Dial Before You Dig.
Never assume that the plans you receive from your inquiry contain the exact location of the underground assets. Assets still need to be carefully and physically located for confirmation.
Cables are typically buried at between 450 mm and 1000 mm, but soil may have been inadvertently removed from above the assets or more soil may have been deposited above them. Never assume cables or pipes will be located at a consistent or required depth.
Lodge your application for digging near underground infrastructure with Dial Before You Dig. You can also call their national call centre on 1100. Dial Before You Dig will provide you with the contact details of the infrastructure owners on the enquiry confirmation sheet. The owners may provide additional information or instructions on locating and working near their underground networks.
Check location with cable and pipe detection
One way to take the worry out of locating buried underground assets is to use the services of an accredited underground asset location company.
If you are using your own locating equipment, it is important to ensure that the operators are trained in its use and are aware of its limitations. In addition, the equipment must be calibrated and capable of detecting all types of cables and pipes as necessary. Some locating equipment may not detect an electric cable unless there is current flowing and may not be able to detect non-metallic pipes or conduits.
It is common for gas assets to be laid in polyethylene (PE) pipe (yellow or black with yellow stripes). Generally, PE pipe is laid with detectable (foil backed) marker tape or non-detectable marker tape and a tracer wire, however, this is not always the case.
Check location with a pilot or trial hole
Once the asset location has been determined, a pilot or trial hole should be used to establish the exact location and depth of the asset.
Using insulated hand tools is considered a safe method for excavation, but they can also be a common source of accidents and cause damage to the asset if used incorrectly.
Other safe methods of excavating include water jetting and high-velocity air jets incorporating vacuum removal of excavated soil to expose buried assets. Their use may be limited by the ground conditions and soil type. Precautions are also needed to prevent injury from ejected soil. Whichever method is chosen, you need to apply it with care.
Before digging or water jetting near a high voltage electrical cable, check with SA Power Networks on 1300 650 014 or ElectraNet on 1800 243 853 if there are any special conditions that apply.
Machinery - dig at a safe distance
Once an asset location has been determined, excavation may proceed. Every effort should be made to excavate alongside the service rather than directly above it. Extreme care should be taken when digging above or close to the determined asset location.
Marker tape is commonly used as a location indicator for buried pipes and cables. If a marker tape is found, use extreme caution if you continue digging.
Hand-held power tools and mechanical excavators must be used with extreme care when working close to underground assets.
A risk assessment should be used to determine the minimum safe working distance for powered tools and excavators from the underground assets.
Final exposure of the asset by horizontal hand digging is recommended, as the force applied to hand tools can be controlled more effectively.
Insulated tools (eg spades and shovels, preferably with curved edges) should be used when hand digging near electric cables. They should not be thrown or spiked into the ground but eased in with gentle foot pressure.
Electricity network access permits and notification
Where possible the electricity supply to the underground cable should be isolated before digging.
If you need to isolate an SA Power Networks cable you will need to apply for a network access permit from SA Power Networks. The permit will ensure the powerlines will be turned off until the permit is returned.