Quality levels

The recommendation on this page is awaiting named sign-off before it is treated as published (Sprint A §A7.2).

QL-B across the corridor before design locks. QL-A at every point you intend to break ground.

Classification of subsurface utility information is set out in AS 5488.1:2022 and AS 5488.2:2022. This page describes the framework in our words. It does not reproduce the standard, and it does not claim the business is “AS 5488 compliant.”

QL-D

Existing records and Before You Dig Australia responses. No field verification. What you get is what someone once wrote down, or what a network operator still has on file.

Plans are frequently wrong. Assets went in before anyone kept a useful record. As-builts often record the intended run, not the finished one. Abandoned services stay in the ground and on the plan. A QL-D picture is a starting point, not a place you can design or dig from.

QL-C

Surface features surveyed — pits, markers, visible plant. That tightens the picture. It still infers what runs between two known points. The ground between the pits is a guess with better endpoints.

QL-B

Geophysical detection — electromagnetic locating and ground-penetrating radar — corridor-wide, coordinated with survey pickup, before design locks. This is the level that belongs on a corridor while there is still time to move a trench or a footing.

It has limits. Non-conductive pipe without tracer wire can be silent. Congested corridors couple signals. Depth beyond effective range is not a detection, it is a gap. QL-B infers. It does not confirm.

QL-A

Physical exposure by non-destructive digging, then survey. The only level that confirms rather than infers. That is why it belongs at every point you intend to break ground — not as a corridor-wide default, as proof at the conflict.

When QL-A is not needed

Concept and feasibility work does not need potholes. Neither does a corridor where nothing will be excavated. Recommending the highest level for every metre of a site is a sales page. We do not do that.