Guide
Digging near underground services: locate, pothole, then dig
Digging safely near underground services in NSW means a BYDA (Before You Dig Australia) enquiry, locating, potholing to confirm the service, and only then digging. Spot On Excavations, based in North Richmond, NSW, sets out that order of work for site managers, electricians and project engineers.
Start with a BYDA enquiry
Before You Dig Australia (BYDA) is the free referral service that tells you which asset owners have services near your work. You lodge an enquiry with the location and the type of work, and the asset owners send back plans. Lodge it before any dig, every time, and check the dates, because plans lapse and the site can change.
What the plans do tell you: that there is an asset owner with something in the area, roughly what it is and roughly where. What they do not tell you: the exact depth, whether the line has been moved, abandoned or never recorded, or whether private services on the site (a customer’s own supply, irrigation, a sub-main) are shown at all. Treat plans as a prompt to look further, not as a location.
AS 5488 quality levels
AS 5488 describes how much you actually know about a service’s position, in four levels from QL-D to QL-A. QL-D is records only. QL-C adds surface features such as pits and covers. QL-B is a trace with an electromagnetic locator or similar. QL-A is a physically exposed and measured service. The lower the letter, the more certain the position. Ask what quality level a plan or marking represents before relying on it. Our page on potholing explains how QL-A is reached.
Locating: what a locator can and cannot find
An electromagnetic locator, such as our Radiodetection RD8200, picks up a signal on a metallic service, either one the service is already carrying or one that is put onto it. A trained operator uses it to trace the line across the surface and mark it.
- It is good at finding live cables and metallic pipes that can carry a signal.
- It can miss plastic pipe and conduit without a tracer wire, services with a broken or poorly connected tracer, and anything buried among other signals.
- Its depth reading is an estimate and can be thrown off by interference.
- It does not tell you what a service is, only that one is there.
A locate is a strong step, but it stays a QL-B result, and it does not prove the area is clear.
Potholing is the only way to confirm
To know where a service is, you expose it. Vacuum excavation does that with water and suction, so no hard edge touches the cable or pipe. A pothole gives you depth and offset you can measure and record. If your trench or bore has to pass close to a service, pothole at the crossing and along the line before the machine arrives. That is our approach for horizontal directional drilling work too.
Safe approach distances
How close you can dig, with what tool, is a rule set by the asset owner, and it differs between electrical, gas, water and telecommunications assets. Get the asset owner’s written conditions for working near its service and follow them. If the conditions say hand dig or non-destructive methods inside a zone, then that is the method. We do not quote distances here because the owner’s rules are the only ones that apply to your job.
Hand digging or vacuum excavation
Hand digging with insulated tools is permitted by many asset owners inside a zone, and it works for a shallow hole or a short run. It is slow, hard on workers over a long run or in heavy ground, and it still puts a tool near the service. Vacuum excavation is faster over a lot of holes or in dense ground, moves the spoil into a tank, and keeps the work cleaner. Which is better depends on what the asset owner allows, how much there is to dig, and the ground. Many jobs use both.
If you hit something
- Stop work and stop the machine. Do not move or touch the service.
- Keep people clear and treat an unknown cable as live.
- Make the area safe and call emergency services if there is a gas smell, a fire, a flooding main or an electrical hazard.
- Notify the asset owner immediately, using its emergency number.
- Do not backfill over the damage. Record what happened with photos and notes.
- Restart only when the asset owner and your supervisor agree it is safe.
The sequence in short
- Lodge a BYDA enquiry and read the plans.
- Get the asset owner’s conditions for working near their service.
- Locate the services on site and mark them.
- Pothole at crossings and along the line to reach QL-A.
- Plan the trench or bore depth from the measured result.
- Dig by the method the asset owner allows, with a spotter and a method statement.
If you want us to run steps 3 and 4, see vacuum excavation. If you also need a bore, we do that under horizontal directional drilling. Or contact us to talk it through.
Questions
Digging near services questions
Is a BYDA enquiry enough to dig safely?
No. It tells you who to ask and gives you plans of variable accuracy. You still need the asset owner’s conditions, a locate, and potholing where the work is close to a service.
Can a locator tell me how deep a service is?
It gives an estimate that can be wrong, particularly near other services or in difficult ground. Only an exposed service gives a depth you can rely on.
Do plastic pipes and conduits show up on a locator?
Not unless they have a working tracer wire or a trace is introduced another way. Their absence from a locate does not mean they are not there.
Who decides how close I can dig?
The owner of the asset. Ask for its written requirements for working near its cable or pipe and follow them.
Do you do the locate and the pothole together?
Yes, on most jobs. We trace with our RD8200 locator, then pothole at the points that matter and record each result.
Can you do this ahead of a drilling job?
Yes. This is a common use for our trucks. We do it ahead of our own bores and for other drilling crews.
Related
Next step
Want services proved before you dig?
Send us the site and the line of work. We will locate, pothole and give you the results in writing.