The British Standards Institution (BSI) withdrew PAS 128:2014 on 26 April 2022. The document that replaced it, PAS 128:2022, sets out its quality levels under different names.

Why the edition date matters

A scope of works or a survey report that still refers to QL-A, QL-B, QL-C or QL-D is written against the withdrawn edition. A surveyor working to that wording is either using an outdated document or translating it into current terms on the fly, and neither is something a buyer should have to guess at. If you're checking a specification someone else wrote, the quality-level names it uses tell you which edition it was written against before you read another word of it.

Where the current standard is explained

The Chartered Institution of Civil Engineering Surveyors (CICES) published a client guide to PAS 128:2022 in September 2022. It sets out the current standard for the person commissioning a survey.

Once you know which edition applies, the next question is which quality level your job actually needs, and where a clause for it belongs in the tender. See the scope-of-works wording keyed to PAS 128:2022 for that.

A survey comes back marked with a quality level, and that mark records a method. Each level in PAS 128:2022 corresponds to a specific way of finding out where a buried service sits, and the level tells you how much of that finding-out has actually been done.

What separates B3, B2 and B1

The three levels a buyer deals with build on each other, and the difference between them is the amount of independent checking behind the plotted position.

• B3 comes from records and a walk of the site: utility company plans, apparatus plans, and what can be seen above ground. Nothing has been detected in the ground itself, so a service can be missing from the plot entirely if the records are wrong or out of date.
• B2 adds a detection method run over the ground, commonly ground penetrating radar or electromagnetic location, to plot what is actually there. The position shown is still inferred from a surface reading.
• B1 adds a second, independent detection technique over the same ground and reconciles it against the first. Two methods agreeing on a service's position is a firmer basis for design than one, though the service still has not been physically exposed.

Why the order matters when you specify

A buyer usually meets B2 first, because it is the level most commonly quoted for a routine detection survey, and only asks about B1 once the design has to go closer to a service than a single detection pass can support with confidence. Specifying a level higher than the job needs adds survey cost for no design benefit; specifying one lower leaves the design resting on records or a single reading. The wording you use to ask for a given level in a scope of works is set out on Specifying it in a scope of works.

A PAS 128:2022 quality level answers a question about a buried service based on what has been surveyed and how. Confirming that answer on the ground is a separate step, and PAS 128:2022 does not insist on a trial pit to do it.

What the CICES guide says about verification

The CICES Client Specification Guide (September 2022) confirms that verification by excavation may be by vacuum excavation or suction excavation as well as by trial pit. Where a specification calls for excavation to confirm the position, depth or condition of a service, that confirmation does not require a hand-dug pit as the only accepted method.

This matters at the point a scope of works is being written. A clause that names "trial pit" as the sole verification method rules out a technique that the guide already treats as equivalent for this purpose, and rules it out without any requirement forcing that choice.

Where this sits against the survey level

The quality level tells you how the information about a service was produced. Verification by excavation is a separate check, applied where the job needs certainty that a desktop or geophysical result alone cannot give. Choosing vacuum or suction excavation for that check is a technique decision, and the ground condition and asset type at the location govern which technique is appropriate.

For that decision, see Suction, Air and Water — Which Suits This Ground. For wording that carries the verification method into a tender document, see Specifying It in a Scope of Works.

The PAS 128:2022 quality level a job needs depends on what the buried-service picture already looks like before you start, and on what decision the survey has to support once it is finished.

Start with what you already know

If the asset owner's records for the site are thin, or the ground has been reworked since they were drawn, a survey has to establish more before it can confirm anything. If a plant-protection specification already fixes the position of the assets that matter to your works, the survey's job may be narrower: confirming what is already claimed.

Match the level to the decision it feeds

A feasibility study deciding whether a route is viable at all needs a different degree of certainty than a detailed design being issued for construction, and a principal designer signing off a permanent works drawing needs a different degree again from a site manager deciding whether to open a trial hole tomorrow. Specify the level for the decision in front of you.

Higher confidence costs more to establish

Each additional survey technique stacked onto a desk study, geophysical detection or verification adds time and cost to the job. A level asked for out of habit is a cost with nothing behind it. Specifying it in a scope of works sets out how to state the level so a contractor can price it against what is actually required.