The standard
PAS 128 survey: the quality levels, and when you need one
Updated
A PAS 128 survey is a utility survey done to BSI's PAS 128, the UK specification for detecting, verifying and locating buried utilities, and the survey asked for on most design and groundworks jobs is Quality Level B: detection on site with GPR and EML.
The four quality levels
- QL-D: desktop records search
- The asset owners' plans, collected and put on one drawing. Nothing is detected on site.
- QL-C: site reconnaissance
- The records checked against what can be seen on site: covers, chambers, marker posts.
- QL-B: detection
- Services found on site with GPR and EML and marked up, with an accuracy grade for each.
- QL-A: verification
- Services exposed in trial holes so their position and depth are measured, not inferred.
Spatial Dimensions prices QL-A verification separately, per trial hole, from £350; Groundwise prices a QL-D records search from £100 plus VAT.
Source: Spatial Dimensions: PAS 128 utility surveys, read 28 October 2026
What HSE asks before anyone digs
HSE's guidance HSG47, Avoiding danger from underground services, sets out the three basic elements of a safe system of work during excavation: planning the work, locating and identifying buried services, and safe excavation. A utility survey is the second of the three.
Source: HSE HSG47: Avoiding danger from underground services
The records you can get first
The National Underground Asset Register (NUAR) is a digital map of underground pipes and cables for England, Wales and Northern Ireland, with data from over 600 public and private sector asset owners; the Data (Use and Access) Act, which received Royal Assent in June 2025, puts it on a statutory footing. GOV.UK says that without it workers must contact multiple organisations and wait on average over six days for the information.
Source: GOV.UK: National Underground Asset Register (NUAR)
LinesearchbeforeUdig is a free online enquiry service that checks a dig site against its member asset owners' records.