AS 5488 Quality Levels Explained: QL-A to QL-D for NSW Sites

AS 5488 is the Australian Standard that classifies how reliable underground utility information is, using four quality levels from QL-D (records only) to QL-A (physically exposed and surveyed). At Dowd's Pipe and Cable Locating, we work to AS 5488 on sites across Wollongong, the Illawarra and Sydney, and knowing which quality level your data sits at tells you how safely you can dig.

Key Takeaways

• AS 5488 sets four quality levels for subsurface utility information: QL-D (plans and records only), QL-C (records tied to visible surface features), QL-B (located in the field with instruments) and QL-A (physically exposed and surveyed).
• The standard gives designers, contractors and asset owners a shared language for how much confidence to place in a utility's position before excavation.
• Higher quality levels cost more to collect, but they cut the risk of utility strikes, outages and redesigns where it matters most.
• Choosing the right quality level for each project phase and work zone is how you balance cost against risk.
• We deliver AS 5488 compliant reporting with GPS-referenced PDF reports and colour-coded site markings across Wollongong, the Illawarra, the South Coast, Sydney metro and the Southern Highlands. Call 0434 635 134 to talk through your project.

AS 5488 and the Classification of Subsurface Utility Information

AS 5488 is the Australian Standard for classifying subsurface utility information, published by Standards Australia. Since 2019 it has been split into two parts: AS 5488.1, which covers the classification of subsurface utility information, and AS 5488.2, which covers subsurface utility engineering (SUE). Always check you are working from the current edition for contractual or compliance purposes.

The standard covers the buried services you'll find on almost any site in NSW, including power, telecommunications, gas, drinking water, sewer, stormwater, drainage and fire services. It doesn't tell you where a service is. It tells you how that position was obtained and how much you can rely on it.

Councils, utility owners and civil contractors across Wollongong, Sydney and the Southern Highlands increasingly write AS 5488 quality levels into project briefs. At Dowd's Pipe and Cable Locating, we classify every service we record against the standard so your design team knows exactly what it's working with.

Overview of AS 5488 Quality Levels (QL-A, QL-B, QL-C, QL-D)

The four AS 5488 quality levels form a hierarchy from QL-D, the least reliable, to QL-A, the most reliable. Each level describes both how the information was collected and how much confidence you can place in its position.

• QL-D: drawn from existing records only, such as Before You Dig Australia (BYDA) plans and as-constructed drawings.
• QL-C: records tied to visible surface features like pits, valves, hydrants and manholes.
• QL-B: services detected in the field with instruments such as electromagnetic locators and ground penetrating radar (GPR), then surveyed.
• QL-A: services physically exposed, usually by vacuum excavation, and surveyed in place.

The levels also line up with project phases. QL-D and QL-C suit early planning and feasibility. QL-B supports detailed design and clash detection. QL-A is for high-risk construction zones and final set-out around critical services. We help builders and civil contractors in Wollongong and Sydney work out which level each part of a site needs.

Quality Level A (QL A): Exposed and Surveyed Utilities

Quality Level A is the highest level in AS 5488: the service has been physically exposed, visually confirmed and surveyed in place. It's the level you want before mechanical excavation close to gas mains, high-voltage power, major water mains or critical fibre.

On site, QL-A usually comes at the end of a sequence. First, electromagnetic locating and GPR establish the likely position. Then vacuum excavation (also called potholing or non-destructive digging) exposes the asset without damaging it. Once it's exposed, we record depth, offset, material, size and condition, and capture the position with GPS coordinates.

Only the exposed points are QL-A. The sections between potholes stay at the level they were located to, usually QL-B. At Dowd's Pipe and Cable Locating, we combine detection with vacuum excavation and record the QL-A points clearly in our AS 5488 compliant reports. That way you can see exactly where the ground has been physically verified.

Quality Level B (QL B): Instrument-Located Utilities

Quality Level B covers services located in the field with instruments, without exposing them. It's the workhorse level for design, investigation and pre-construction work across Wollongong and Sydney.

Two technologies do most of the work:

• Electromagnetic (EM) locating applies or picks up a signal on conductive services such as power cables, metallic pipes and some telecommunications cables, then traces it at the surface.
• Ground penetrating radar sends radar pulses into the ground and reads the reflections. That makes it effective for non-metallic services like PVC pipes, concrete conduits and fibre lines that EM can't find.

QL-B gives designers a reliable relative position for clash detection, but depth is still an estimate and accuracy depends on soil, moisture and congestion. Near pressurised gas or high-voltage power, QL-B is usually upgraded to QL-A at the critical points. We deliver QL-B outputs with GPS-referenced coordinates, colour-coded site markings and quality levels labelled in each PDF report. If you're new to how the two methods differ, our guide to how GPR and EM locators detect hidden pipes covers it in more detail.

Quality Level C (QL C) and Quality Level D (QL D): Plan-Based Information

QL-C and QL-D both come from records rather than field detection, so they carry the most positional uncertainty.

QL-D is the lowest level. It's based on utility plans, BYDA responses and other records, with no field verification. It's useful for very early assessments, but services can be well away from where they're drawn.

QL-C improves on QL-D by tying records to visible surface features such as hydrants, manholes, valve boxes and marker posts. That confirms where a service enters and exits a site, but not the alignment or depth in between.

Relying on QL-D or QL-C data for excavation is where most utility strikes start. On older sites around Wollongong and Sydney, records often don't reflect decades of changes. At Dowd's Pipe and Cable Locating, we include existing record information in our AS 5488 compliant plans but label it clearly as QL-C or QL-D, so you can see where further investigation is worth the spend.

How AS 5488 Quality Levels Apply to Different Utility Types

AS 5488 quality levels apply to every type of buried service, but the consequences of getting the position wrong vary by asset. That's why the level you need depends on what you're digging near.

• Power: underground electrical cables carry the risk of electrocution, arc flash and outages. Before mechanical excavation near high-voltage cables, QL-B at minimum and QL-A at crossings is standard practice.
• Telecommunications: fibre and copper networks carry NBN, traffic signals and business connections. A single strike can take out a whole street, so QL-B mapping is a sensible baseline in busy corridors.
• Water, stormwater and sewer: a struck pressurised water main can flood an excavation. QL-B supports design of new connections, while QL-A is warranted where new works cross major mains.
• Gas: gas mains demand the most caution. Asset owners such as Jemena commonly expect services to be positively located before excavation within set distances.
• Fire services: hydrant and sprinkler mains are easy to overlook on commercial sites and should be located and classified like any other service.

We locate all of these across the Illawarra, South Coast, Sydney and the Southern Highlands and classify each one to AS 5488.

Ground Penetrating Radar, EM Locating and Vacuum Excavation Under AS 5488

AS 5488 doesn't name equipment brands, but in practice three methods do most of the work of reaching QL-B and QL-A.

• Ground penetrating radar finds non-metallic services, trench lines and unknown structures that EM can miss.
• Electromagnetic locating traces conductive services such as power, telecommunications and metallic pipes with high precision. Multi-frequency EM helps separate services that run close together.
• Vacuum excavation uses water or air pressure and suction to expose services without mechanical digging, upgrading key points to QL-A.

The methods complement each other, and no single one sees everything. At Dowd's Pipe and Cable Locating, we combine all three on site in Wollongong and Sydney and record which method was used for each feature in our reports.

AS 5488 Colours, Marking Conventions and Reporting

Field markings and reports work together under AS 5488. Colour-coded paint on the ground shows crews what each service is, and the report records the quality level behind each line.

On site, we mark services with standard colour codes and letter labels, plus depths and notes where they're useful. In the report, each service carries its AS 5488 quality level in the legend. A designer can then see not just that a line is gas or power, but whether it is QL-A, QL-B, QL-C or QL-D.

Where surface conditions force a change, such as a light colour on pale concrete, the variation should be noted in the report. Our GPS-referenced PDF reports let designers overlay quality level data onto survey and design models, and we can provide CAD-compatible files and GIS data on larger projects.

Why AS 5488 Quality Levels Matter for Safety, Cost and Program

AS 5488 quality levels matter because poor subsurface information is behind most utility strikes, unplanned outages and costly redesigns on NSW construction sites.

Moving critical areas from QL-D to QL-B or QL-A reduces the chance of hitting a gas main or severing a fibre trunk. The cost of a proper investigation is small next to emergency repairs, program delays and claims from asset owners.

There's a compliance side too. Under the NSW Work Health and Safety Act 2011 and the SafeWork NSW Code of Practice for Excavation Work, you must take reasonable steps to identify underground services before excavation. AS 5488 classified reporting is clear evidence that you did. Using the quality levels as a common language between designers, locators, builders and asset owners also cuts down on confusion as a project moves from design to construction.

Working With an AS 5488 Compliant Locator in NSW

An AS 5488 compliant locator should give you clear quality levels on every plan, a description of the methods used and GPS-referenced outputs you can rely on.

Dowd's Pipe and Cable Locating is based in Wollongong and accredited with Dial Before You Dig (DBYD), Telstra, NULCA and Certloc. We bring more than 25 years' experience in civil and underground work to every job. After each locate you receive colour-coded site markings, a GPS-referenced PDF report with AS 5488 quality level classifications, and photographs of markings and any exposed services.

If you're planning civil works, a subdivision or a commercial build in Wollongong, Shellharbour, Campbelltown or anywhere across Sydney, talk to us early about which quality levels suit each part of your site. Call 0434 635 134 or find out more about our underground utility locating services.

Frequently Asked Questions about AS 5488 Quality Levels

Do I always need Quality Level A before I start digging?

No. QL-A is usually needed only where mechanical excavation will happen close to critical services such as gas mains, major water mains or high-voltage power, or where an asset owner requires it. Lower-risk areas are often adequately covered by QL-B. The right mix of QL-A and QL-B is best decided during design, with input from the asset owners and your locator.

How do AS 5488 quality levels relate to Dial Before You Dig (DBYD) plans?

BYDA plans (formerly Dial Before You Dig) are QL-D information: records that show where services may be, without field verification. AS 5488 encourages upgrading that information to QL-C, QL-B or QL-A depending on the risk, by combining plans with field locating and, where needed, potholing. As DBYD-certified locators, we can interpret the plans on site and collect higher-quality data. For more on what to do if things go wrong, see our guide on what to do if you hit an underground utility line.

Can ground penetrating radar see every underground service on its own?

No. GPR performance depends on soil type, moisture, depth and what the service is made of, and clay or wet ground can limit it. That's why QL-B work typically combines GPR with electromagnetic locating. Reaching QL-A still requires physically exposing the service with non-destructive excavation.

What happens if services on site do not match the plans?

It's common, especially on older sites. Under AS 5488, the field-located data (QL-B or QL-A) should be captured and reported so designers and asset owners can update their records and adjust construction methods. Our GPS-referenced reports document these differences clearly.

How do I know which AS 5488 quality level my current utility information is?

If it comes only from plans or BYDA responses, it's QL-D. If it's tied to surface features without instrument locating, it's likely QL-C. Instrument-located and surveyed data is typically QL-B, and records showing potholing and visual confirmation point to QL-A. If you're unsure, call Dowd's Pipe and Cable Locating on 0434 635 134 and we'll help you check what you've got.