If you’re going to dig, whether foundations, drainage, service trenches or piling, you need to know what’s already in the ground. Striking a gas main or power cable can kill. Even a damaged water pipe or fibre line can stop a site and cost thousands. A utility survey finds and maps buried services before you design or dig.
When you need one
- Before excavation of any kind on a site you don’t fully know.
- Before designing foundations, drainage or new service connections, so the design doesn’t clash with what’s there.
- On brownfield and infill sites, where old and undocumented services are common.
- When a principal designer or contractor asks for it as part of your pre-construction information under CDM 2015.
Utility company record plans are a starting point, but they’re often incomplete or inaccurate, and they rarely show private services.
PAS 128 survey levels explained
PAS 128 is the UK specification for underground utility detection, verification and location. Surveys are graded by quality level:
- QL-D, desktop: collecting existing records from utility companies.
- QL-C, site reconnaissance: matching records to visible features such as covers, valves and marker posts.
- QL-B, detection: locating services with electromagnetic location and ground penetrating radar (GPR). This is the level most construction sites need.
- QL-A, verification: exposing services, for example with trial holes or vacuum excavation, to confirm exact position and depth.
We arrange PAS 128 utility surveys with CAD drawings you can drop straight into your design, quoted with any other surveys your site needs.
What you get
A CAD drawing showing each service by type, with its position and, where it can be found, its depth. You also get notes on survey quality and any areas that couldn’t be surveyed. Many clients order a topographical survey at the same time so everything sits on one drawing.
Related services: Utility Surveys, Utility Applications (new connections), Geotechnical Site Investigation.
Frequently asked questions
Is a utility survey a legal requirement?
There’s no single law that says “get a utility survey”, but you have legal duties to work safely near buried services. HSE guidance (HSG47) expects services to be located before you dig. On most commercial and development sites a survey is the normal way to meet those duties.
What is the difference between a utility survey and utility records?
Records are the utility companies’ own plans, which are often out of date and don’t show private services. A survey physically detects what is actually in the ground.
What PAS 128 level do I need?
Most construction sites need QL-B detection. Add QL-A verification at critical points, such as where you’ll dig close to a major service.
How long does a utility survey take?
Fieldwork for a typical residential plot takes a day or less. Larger sites take longer. Drawings normally follow within a few working days.
Last reviewed: October 2026. General guidance for England only. Rules change and every site is different, so get project-specific advice before relying on it.
More guides in the Developer Knowledge Centre · Services: Utility Surveys, Utility Applications