What is an Underground Utilities Survey?
Before excavation on site, it’s crucial to be aware of what services might be present below ground. An underground utilities survey, or underground services survey maps the location, type, size, depth, and quantity of underground services. This helps to reduce risk when excavating, saving time, and preventing costly and dangerous utility strikes. Our methodology aligns to BSI PAS 128:2022 (Types D→A) and best practice from the RICS Measured Surveys of Land, Buildings and Utilities (3rd ed.)
Case Study: Stansted Airport
Case Study: RAF Alconbury
When do I need an Underground Utilities Survey?
An underground services survey is a component of risk management and health and safety compliance. Excavating without knowledge of what lies beneath the surface has the potential to harm both operatives and the public. Therefore an underground services survey is crucial wherever excavation works are taking place be it for boreholes, trial pits, or foundations.
Under the Health and Safety at Work etc. Act 1974 and the Construction (Design and Management) Regulations 2015 (CDM), there is a legal duty to provide a safe system of work. An accurate utilities survey can help to ensure this is the case in alignment with UK Health and Safety Guidance 47 – “Avoiding Danger from Underground Services”.
A clear picture of where services are running is crucial not only in reducing risk of harm to individuals but also in reducing costly utility strikes and consequent delays and disruption. UK data shows tens of thousands of accidental service strikes each year with estimates putting the total direct and indirect cost at approximately £2.4 billion annually. In recent case studies, the true cost of a single strike can be around 29× the direct repair cost once delays, rework, traffic disruption, and societal impacts are accounted for.
Minimise disruption and delays with reliable, asset-rich CAD/GIS deliverables for designers and site teams.
Improve reputation and compliance by adopting the UK’s recognised specification (PAS 128:2022).
Underground Utilities Surveys deliverables
- Full PAS 128 Utility Surveys in 2D or 3D, Types D, C, B, and Type A supervision (with works carried out by approved sub-contractors)
- EML & GPR detection, drainage connectivity surveys, and service/void location
- Procurement of Statutory Records (STATs) and comprehensive desktop search (Type D)
- “Service clearance surveys” and markout, referenced to PAS 128 quality levels
- Integrated topographical control and geospatial deliverables (CAD/GIS)
PAS 128 Survey Pathway (Type D → C → B → A)
Type D – Desktop Records Search
We contact all relevant utility owners and compile statutory plans into one comprehensive report – the prerequisite to type C, B and A work, and ideal for early design (must be current – within 3 months for follow on surveys).
Type C – Site Reconnaissance
A visual walkover validates records against aboveground evidence (covers, markers, cabinets) to refine the picture before detection, combined with an accurate “Topographical Survey”
Type B – Detection
Our surveyors combine Electromagnetic Location (EML) with Ground Penetrating Radar (GPR) for both metallic and non-metallic utilities (e.g., plastic water mains), and conduct drainage connectivity surveys recording location, type, size, depth, and quantity of underground services and anomalies. These are assigned a Quality Level given the achieved accuracy found on site for each utility and provided as CAD deliverable with a topographical survey used as a backcloth.
Don’t have a current “Topographical Survey”? We can also carry this out for you alongside the utility survey.
Type A -Verification
Where required, we supervise trial holes and excavations for verification, achieving the highest confidence (QLA) for critical assets.
Tools & Techniques
We use EML to transmit and receive signals on conductive targets (e.g., power, communications, metallic water/gas), GPR to image subsurface profiles and detect metallic/nonmetallic utilities, voids and tanks, and visual/drainage inspections to confirm connectivity. All detections are surveyed with total stations/GNSS for accurate georeferencing
