Underground Utility Surveys in London and the UK
An underground utility survey locates and maps the buried services beneath a site, gas, electricity, water, telecoms, drainage and more, before anyone breaks ground. For contractors, engineers and designers, it is one of the cheapest forms of risk management available. A single service strike can injure people, halt a programme and run to serious cost, and almost all of them come down to not knowing what was below the surface.
Scan Surveys carries out utility surveys across London and the wider UK, working to PAS 128, the British standard for underground utility detection, verification and location. PAS 128 gives the whole project team a common language for how a survey was done and how far its findings can be relied upon, so a utility map is no longer just a drawing but a stated level of confidence.
We combine complementary detection techniques on site, then deliver a clear, coded utility drawing you can design and dig against. Where the standard’s higher confidence levels are needed, we can take the survey through to physical verification.
What we capture and deliver
We detect buried services using more than one method, because no single technique finds everything:
- Electromagnetic location (EML) detects metallic and conductive services, such as electricity cables, and metal water and gas pipes, and can trace live cables.
- Ground penetrating radar (GPR) detects non-metallic services that EML cannot pick up, including plastic pipes, ducts and fibre optics, as well as voids and subsurface features.
- Signal tracing and sondes locate non-conductive pipes and drainage runs where a trace can be applied.
Using these together gives far more complete coverage than any one method alone. Results are recorded and delivered as a coded utility drawing in CAD (DWG/DXF), with the survey classification and a method statement setting out how the work was carried out and its limitations, as PAS 128 requires.
When you need it
A utility survey belongs at the front of any project that disturbs the ground:
- Before excavation, to reduce the risk of striking a live service
- Design and coordination, positioning foundations, drainage and new services around existing ones
- Pre-construction and site set-up, informing safe digging and method statements
- Development feasibility and due diligence, understanding what constrains a site
- Asset management, recording and maintaining buried infrastructure
If your programme includes digging, piling, trenching or foundation work, knowing what is below first protects both people and the schedule.
Deliverables
- Coded utility drawing in CAD (DWG/DXF) to PAS 128
- Survey classified against PAS 128 quality levels
- Method statement covering equipment, technique, coverage and limitations
- Detection using EML and GPR, with tracing where applicable
- Optional verification to QL-A by trial hole or vacuum excavation
A survey you can plan around.
A clear, repeatable method on every job, so you know what is happening on site and what lands on your desk afterwards.
Scope
We agree the PAS 128 quality level required, the site extent and any known risks, so the survey is specified to the confidence your works demand.
Records and reconnaissance
Where required we begin with a records search and a site walkover to correlate statutory plans against visible surface features.
Detect
We survey on site with EML and GPR, applying signal tracing where services can be traced, following a defined detection methodology and grid.
Deliver
We produce a coded CAD drawing with the PAS 128 classification and a method statement, and can progress to physical verification where the highest confidence is needed.
Questions we are asked about this service.
What are the PAS 128 quality levels?
PAS 128 defines four quality levels of increasing confidence. QL-D is a desktop records search with no site work. QL-C adds a site reconnaissance, visually correlating records against surface features. QL-B is a detection survey using geophysical methods such as GPR and EML to locate services on site, and is itself subdivided from B1 to B4 by confidence. QL-A is verification, physically exposing a service by trial hole or vacuum excavation to confirm its position, depth and type, and gives the highest confidence.
What is the difference between GPR and EML?
EML, electromagnetic location, detects metallic and conductive services such as electricity cables and metal pipes, and can trace live cables. GPR, ground penetrating radar, detects non-metallic services that EML misses, including plastic pipes, ducts, fibre optics and voids. Because each finds things the other cannot, a thorough survey uses both together.
Which PAS 128 quality level do I need?
It depends on your project stage and risk. QL-D or QL-C can suit early feasibility and design awareness. QL-B, a full detection survey, is the most widely used level for detailed design and pre-excavation work. QL-A verification is used selectively in high-risk zones, for example near high-pressure gas mains, where absolute certainty is needed. Many projects use a layered approach, building confidence where it matters most.
Will a utility survey stop me hitting a service?
A PAS 128 utility survey significantly reduces the risk of a service strike by locating and mapping buried services before you dig, but no detection survey can guarantee that every service is found, particularly non-conductive or poorly recorded ones. That is why detection is paired with safe digging practices, and why critical services are verified physically at QL-A before excavation.
What deliverables do I get from a utility survey?
You receive a coded utility drawing in CAD (DWG/DXF) showing the located services, classified against the PAS 128 quality levels, together with a method statement setting out the equipment used, the detection approach, the areas covered and any limitations. This is the record you design and plan safe excavation against.
Can you carry out the survey on a live or occupied site?
Yes. EML and GPR detection are non-intrusive, so surveys can be carried out on live and occupied sites with appropriate access and traffic management. Where physical verification to QL-A is required, we plan trial holes or vacuum excavation around site operations and safe digging requirements.
One team, from point cloud to pull test.
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