If you've requested a utility survey quote and seen "PAS128" mentioned, it's worth understanding what that actually means — because the quality level specified directly affects survey cost, time on site, and how much you can trust the resulting drawing.
What PAS128 Is
PAS128 is a published specification for underground utility detection, verification, and mapping. It defines a common set of quality levels so that a client, consultant, and survey provider can agree in advance on exactly how thorough a survey needs to be, rather than leaving "utility survey" as a vague, unspecified scope.
The Quality Levels
PAS128 defines several survey quality levels, ranging from a desktop records review with no physical site detection, through visual and basic detection surveys, up to fully verified surveys that combine multiple detection technologies and intrusive verification at key points. Higher quality levels cost more and take longer, but produce data that designers and excavation crews can rely on with much greater confidence.
Why the Quality Level Matters
A desktop-only review tells you what utility companies have on record — which is often incomplete, especially in areas with decades of undocumented modifications. A detection-level survey adds physical verification using GPR, electromagnetic locating, and radio detection, catching utilities that records missed entirely. The highest quality levels add intrusive verification, physically confirming utility position at key locations through small excavations or trial pits.
For a project where utility strikes carry serious safety or cost consequences — deep excavation, piling, directional drilling — specifying a higher quality level is a small cost relative to the risk being managed.
How to Specify It
When requesting a survey, the clearest approach is to state both the required PAS128 quality level and the intended use of the data. A survey intended purely for early-stage design feasibility has different requirements than one intended to clear an exact piling location for construction. A competent survey provider should be able to recommend the appropriate level once they understand what the data will be used for.
The Bottom Line
PAS128 gives everyone on a project a shared, specific language for survey quality, rather than relying on assumptions. Asking your survey provider which quality level they're delivering — and why — is one of the simplest ways to make sure you're getting data that matches your actual risk on site.