Field guide · Updated April 2026

What every spray mark
on the road actually means.

Eight colours, one underground city. New Zealand follows WorkSafe NZ guidance and the PAS128 framework - but the paint on the road is only useful if you can read it. This guide decodes every colour you'll see before a dig.

4 min readUpdated April 2026Aligned with WorkSafe NZ guidance

standard colours

1×

strike every 60s globally

$30k+

average NZ strike cost

good reasons to guess

Walk down any New Zealand street that's about to be dug up and you'll see them: short, fluorescent paint marks pointing at things you can't see. They aren't graffiti - they're a life-safety system. Each colour represents a different network buried below, and getting them wrong has cost crews their lives.

The convention follows WorkSafe NZ's Guide for Safety with Underground Services. The colours line up with international practice (APWA in the US, DBYD in Australia) so a locator from Sydney can read a job site in Christchurch without a translator.

Markout Decoder

Tap or hover a colour to decode it.

Electric Power

#F97316

Typical depth: Typically 600–1200 mm. Sub‑transmission can be deeper.
Why it matters: Live cables can arc at distance - never assume de‑energised.
Surface cues: Look for road‑surface scarring, pillar boxes and street lighting columns.

The eight colours, in detail

Hover the decoder above to skim, or read on for the full breakdown - depths, hazards, and the little surface clues that tell you something's buried even before the locator turns up.

Orange - Electric Power

Orange is the colour you respect first. Direct-buried LV cables often live just 600 mm down, but HV sub-transmission can sit metres deep with massive current behind it. A modern locator can sense induced fields from energised conductors, but consented de‑energising is the only way to be safe.

Aging paper-insulated lead-covered (PILC) cable is still in service in pockets of older NZ networks. Touching one with the wrong tool can be fatal even if the supply has been switched out at the substation - capacitance keeps it lively for minutes.

✓Treat as live, always.
✓Maintain your locator's stand-off distance.
✓Hand-dig within the tolerance zone.

✕Don't rely on a single sweep - repeat at right angles.
✕Don't break through duct walls with mechanical tools.
✕Don't assume distribution voltage; sub-transmission hides here too.

Yellow - Gas

New Zealand's reticulated gas is mostly medium-pressure polyethylene with yellow PE on the outside, plus a yellow trace tape buried above. A nicked MP main vents until the operator isolates it; a struck transmission line ignites.

Yellow valve covers in the footpath aren't decorative. They mark service tees and isolation points - note them on your dig plan even if your trench is metres away.

✓Stop work, ventilate, and call the gas operator on any nick.
✓Use spark-free tools in the tolerance zone.
✓Track the trace tape ~300 mm above the pipe.

✕Don't smoke or run combustion plant near a leak.
✕Don't backfill until the operator inspects.
✕Don't trust grass-coloured polyethylene - only the marks.

Purple - Communications

Purple covers Chorus copper, fibre, the network operators (Spark/2degrees/One NZ), Vocus and the long-haul backhaul that stitches it all together. Comms ducts are notorious for being shallower than they should be - settlement and surface overlay shifts the cover over time.

A single fibre cut in the wrong place takes out emergency calls for a whole exchange. Operators take outages personally and the invoices reflect it.

✓Expect dense duct banks, especially near pits.
✓Photograph what you expose - operators want this.
✓Check for both copper and fibre on the same alignment.

✕Don't treat fibre as 'just internet'. 111 calls and EFTPOS ride on it.
✕Don't cut a duct to ease access - cores inside may be live.

Blue - Potable Water

Blue is potable water - the network that pressurises every tap in the country. Mains run at 500–800 kPa typically; a struck 150 mm main can empty 20 litres a second into your trench.

Toby boxes at the property boundary mark the start of a service lateral. Older laterals are galvanised steel and can be hard for EM locators to detect - request the operator's standover for anything close.

✓Watch the trench: a slow seep can become a washout fast.
✓Confirm whether you're on the main or a service lateral.
✓Have the operator's number on speed dial - boil-water notices follow strikes.

✕Don't dewater a struck main into a stormwater sump.
✕Don't disturb thrust blocks or bedding around fittings.

Green - Stormwater

Stormwater follows gravity and the council's 1-in-X design storm. Pipes can be reinforced concrete, glazed earthenware on older inner-city streets, or modern HDPE. Depths vary wildly - an outfall can be 300 mm; a trunk drain 4 metres.

Green is the WorkSafe-preferred stormwater colour, but you may still see pink in the field - both are valid. Confirm with the operator who painted them.

✓Treat any open chamber as confined-space risk.
✓Plan around rainfall - a dry pipe can fill in minutes.
✓Capture invert levels if you're re-grading nearby.

✕Don't backfill silt into the line - it ends up in the harbour.
✕Don't cross-connect with sewer; auditors will find it.

Red - Wastewater / Sewer

Red marks the foul drain - the network you absolutely don't want to misidentify. Gravity sewers run deep and steep; pressure mains (often near pump stations) run shallow. Both bring biohazard, and confined-space hazards live in every chamber.

Some councils call wastewater "foul" or "sanitary sewer" on plans. The colour stays the same.

✓Assume biohazard PPE for any exposure.
✓Ventilate before entering any chamber - H₂S accumulates.
✓Notify the operator before any temporary diversion.

✕Don't pump untreated sewer to surface or stormwater.
✕Don't ignore H₂S monitor alarms, even briefly.

Pink - Unknown / Stormwater

Pink is the wildcard. WorkSafe NZ permits it for stormwater, but many crews use it for marks they couldn't identify on the day. Always ask - the difference between "probably storm" and "no idea" is the difference between safe and not.

White - Proposed Excavation

White isn't a utility - it's the dig footprint. Lines, arrows, dimensions and chainage drawn by the planner so the locator knows where to focus. If you find yourself digging outside a white outline, stop and check why.

The standard

PAS128 - how confident is that mark, really?

Colours tell you what. PAS128 tells you how sure we are. The standard grades every utility record from D (a desktop guess) up to A (verified by sight). A good locator marks the colour and writes the quality level next to it.

Desktop record

GIS data only. Could be metres off.

Site reconnaissance

Surface clues confirm the record.

Detection

EML + GPR sweep. Position to ±150 mm.

Verified

Exposed by potholing or hydro-vac.

Before the spade goes in

Reading the colours is step three of a five-step process. Skipping the earlier steps is how strikes happen. Run through this list every time:

1
Pull the digital records
UtilityFinder, beforeUdig and direct from each NUO.
2
Walk the site
Pit lids, valves, hydrants, pillars, surface scarring.
3
Decode the marks
Use this guide. Confirm the locator's PAS128 quality level.
4
Hand-dig the tolerance zone
300 mm either side of any utility, or further per the operator's spec.
5
Document what you find
Photo + survey. Future you will thank present you.

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