How to safely locate underground utilities in New Zealand
Investigating what’s underground is messy and missing something can be life or death. Here’s the five-step process every NZ project should follow.
Most utility locators agree the safest way to investigate underground services is to follow PAS128 or an equivalent staged methodology. PAS128 helps you identify risk early and tighten your tolerance as you get closer to the dig. The framework breaks into five steps; skipping any one of them is how strikes happen.
The five-step process
Plan search
Whatever the project — a retaining wall or a multi-stage highway — start by gathering every plan you can get your hands on. Most plan information is held by Network Utility Operators (NUOs) and comes as as-built drawings or digital GIS records.
UtilityFinder helps with this stage by listing every NUO that serves your area, with their direct contact details and locate-request page in one place. Where operators publish their own asset GIS publicly, we link to it.
Whatever you find online is a starting point only. Always go directly to each NUO for their authoritative, up-to-date records — they'll provide their most current plans and tell you whether you need a standover or specialised locate.
Site reconnaissance
With plans in hand, get on site and look for the surface evidence: manhole covers, valves, pillars, pit lids, surface scarring, and nearby connections to buildings or properties.
Non-invasive detection
With plans plus surface clues, it’s time to detect. The kit is specialised, so hire a professional rather than improvising. Locators use electromagnetic locators (EML), ground-penetrating radar and physical access through manholes and pits. The output is a report and surface marks you can plan from.
Invasive verification
Even after non-invasive detection, ambiguity remains — especially if you plan to dig directly above or across services. Verifying with a physical reveal is often the right call. Verification can be as simple as hand potholing, or as sophisticated as hydro excavation across a wider zone.
Get NUO permission first. Most operators have specific stand-off rules for invasive work near their assets.
Documentation
Document everything you find. A report or marked-up plan proves you took reasonable steps, supports your due-diligence trail, and feeds the next project on the same site.
Share documentation with everyone working on the job. Without it, each new contractor will repeat the work — wasting time and creating more risk.
The kit your locator brings
You won’t use all four on every job — but knowing the difference helps you brief your locator and read their report.
Detects induced fields around energised conductors and signals injected into traceable assets. Fast and portable — the workhorse of most locates.
Pulses radio waves into the ground and images what reflects back. Non-destructive, real-time depth and position. Slower but sees non-conductive assets.
Verification by careful hand digging within a tolerance zone. Slow but unambiguous; the gold standard before any mechanical excavation.
Pressurised water and a vacuum truck remove soil precisely without damaging cables or pipes. The premium verification method.
Conclusion
Locating underground utilities is messy work that rewards careful planning. This is the high-level framework — the detail lives in the WorkSafe NZ guidance and your operator’s site-specific requirements.
Crew safety is the goal. When in doubt, bring an independent locator in — they’ll help you understand the risk and the cheapest way to manage it.
Keep reading
How to locate buried cables in New Zealand
Practical detection methods, EM locator basics, and what to do once you’ve found a cable.
Finding underground utility data in New Zealand
Where to source utility records — NUOs, council GIS, certified locators, beforeUdig.
Understanding utility markout colours
Every spray-paint colour you’ll see on the road, and what each one means.
NZ utility operator directory
Browse every operator we list, by region, with contact details and locate request links.
See what's underground at your address.
UtilityFinder maps NZ utility operators on a single interactive map. Pin your worksite and start your plan search in seconds.