Digging by hand near buried electrical cables is one of the most hazardous tasks a homeowner can undertake — but with the right preparation it can be done safely. The key steps are locating cables before you break ground, using the correct tools, and knowing exactly when to stop and call in a licensed professional.
Why Buried Cables Are So Dangerous
Underground power cables in New Zealand are typically buried at depths ranging from around 500 mm to 750 mm for residential properties, though this varies considerably depending on when the cable was laid, the type of cable, and whether it crosses a driveway or other trafficked area. Older cables may be shallower than you expect, and ground movement over the years can shift them further still.
Striking a live cable with a spade can cause electrocution, severe burns, or death. Even a cable that appears undamaged after a strike may have internal insulation damage that creates a future hazard. WorkSafe NZ treats underground cable strikes as serious incidents, and the consequences — legal, financial, and physical — can be severe.
Step 1: Locate All Underground Services Before You Dig
Before lifting a single spade of soil, you must identify what is buried in your work area. In New Zealand, the standard process is:
- Contact Dial Before You Dig (0800 248 344 or beforeudig.co.nz) — this free service notifies network utility operators (power, gas, water, telecoms) who will provide plans showing their assets in your area. Allow several working days for responses.
- Check your property records and local council — your council may hold as-built drawings showing private service runs from the meter to the house.
- Use a cable and pipe locator — these can be hired from most tool hire shops. They detect live cables and metallic pipes. Note that non-metallic conduit or older unsheathed cables may not be detected reliably.
- Engage a professional locating service — for anything other than very minor digging, a specialist cable locating contractor will use ground-penetrating radar and electromagnetic equipment to give you a much more accurate picture.
Remember: plans show approximate locations only. Always treat the information as a guide, not a guarantee.
Step 2: Understand the Safe Dig Zones
Once you have cable locations marked on the ground (use spray paint or pegs), apply the following rules:
| Distance from marked cable | What you can do |
|---|---|
| More than 500 mm either side | Careful machine digging may be acceptable — check with your network operator |
| 300–500 mm either side | Hand-dig only — no powered tools |
| Within 300 mm | Hand-expose only using a trowel or your hands — no spades or forks |
| Any uncertainty | Stop and get professional advice |
These are general guidelines. Your local lines company (e.g. Vector, Orion, WEL Networks, PowerNet) may have their own specific requirements — always check with them directly.
Step 3: Use the Right Hand-Digging Tools
- Insulated hand tools are not a substitute for locating cables first, but using tools with fibreglass or wooden handles reduces (but does not eliminate) risk if contact occurs.
- Use a flat spade rather than a pointed one — it is less likely to pierce a cable.
- Work parallel to the cable run rather than across it wherever possible.
- Dig in shallow lifts of no more than 50–100 mm at a time as you approach the suspected cable depth.
- Never use a pickaxe, mattock, or powered tool within 300 mm of a marked cable.
- Keep a first aid kit and a charged phone on site at all times.
Step 4: What to Do If You Expose a Cable
If you uncover a cable, stop digging immediately. Do not touch the cable or attempt to move it. Assess whether it is damaged — if there is any sign of damage to the sheath, treat it as live and dangerous regardless of whether the power appears to be on.
- Call your lines company to report the exposed cable and get their advice.
- If you suspect the cable is damaged, call your lines company's emergency line and keep people away from the area.
- Only a licensed electrical worker registered with the Electrical Workers Registration Board (EWRB) may work on or repair a buried power cable. This is restricted electrical work under the Electricity Act 1992 — homeowners cannot legally carry out this work themselves.
Step 5: Reinstatement and Backfilling
Once your work is complete and any cables are safely re-covered, backfill carefully. If the cable was originally protected by marker tape (a brightly coloured warning tape laid above the cable), replace it at the correct depth. If you are laying new services nearby, follow the MBIE Building Performance guidance and your lines company's requirements for separation distances and protection.
When to Call a Professional
Call a licensed professional if:
- You cannot confidently locate all underground services before digging.
- Your excavation is close to the main service entry point or meter box.
- You have exposed or damaged a cable.
- The scope of digging is significant (e.g. trenching across a property).
- You are at all unsure — the cost of a professional locating service or a qualified electrician is far less than the cost of a cable strike.
A qualified excavator or civil contractor will have the equipment, training, and insurance to work safely around buried services. You can find experienced local excavation contractors on tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
