Utility survey before digging
A utility survey before digging locates buried services so excavation can be planned safely and with fewer strikes, diversions, and stoppages. On UK sites that typically combines records searches with on-site detection — often CAT and Genny, ground-penetrating radar (GPR), and targeted trial holes — then marks and documents findings for the dig team.
This site-preparation page is the method owner for utility survey practice in the InfoPage corpus. The guides page with the same slug is a consolidate candidate that should prefer this URL for method depth; leave both URLs live until any redirect is separately approved. Insights on utility interfaces delaying groundworks covers commercial programme impact.
A survey reduces risk; it does not guarantee a clear dig. Records are incomplete, private laterals are often unmapped, and detection has physical limits. Safe dig discipline — permit to dig, hand dig near marks, and escalation on unexpected finds — remains mandatory.
review Groundworks Contractors in Wandsworth and Groundworks Contractors in Kingston.
When sequence matters
Before any mechanical excavation for foundations, drainage, reduced-level dig, or service trenches; when planning consent or CDM arrangements expect service information; when historical plans conflict; or when previous strikes on neighbouring plots raise concern.
It also arises mid-package when enabling or clearance starts without a survey and the first trench finds a live cable — the expensive way to discover you needed one.
Typical sequence
Step 1: Commission records and detection
What this step delivers: Plans and on-site marks available.
Step 2: Confirm critical crossings
What this step delivers: Trial holes expose high-risk services.
Step 3: Issue dig pack
What this step delivers: Marked plans and permit-to-dig process live.
Step 4: Excavate with controls
What this step delivers: Hand dig near services; escalate surprises.
If this matches your project stage, send drawings and site details for a scoped quote — or call to talk through programme and access constraints.
Get an Accurate QuoteWhat each stage delivers
A competent survey pathway usually starts with utility record plans (PAS 128 quality levels are a common UK reference language, but project specifications vary). On-site detection then marks suspected alignments. GPR can help in congested or non-metallic environments. Trial holes expose and confirm critical crossings before plant opens a full trench.
Outputs should include marked-up plans, quality notes, and clear caveats. Surveyors and detection specialists own the survey quality; groundworks teams own safe excavation against that information.
Mainline plans excavation from the survey you provide, uses hand dig or vacuum methods near services as required, and reports unexpected finds. We do not usually perform the full utility survey ourselves unless separately appointed — we still insist one exists before dig.
Differentiate from diversion design: locating services is not the same as relocating them. Diversions need utility-company processes and design; the survey only informs that decision.
Confirm survey currency, quality level, and whether marks on the ground match the drawing. Do not dig on outdated plans alone. Book trial holes at known conflict points before peak dig.
Programme risks and hold points
- No recent utility survey before dig
- Congested urban services likely
- Foundation or drainage trenches crossing known corridors
- Planning or CDM requiring service information
- Previous conflicting or incomplete record plans
Pre-start and handover checklist
- Current utility survey / PAS 128 (or project-equivalent) pack
- Marked-up drawings on site
- Permit-to-dig procedure
- Trial hole plan for conflicts
- Emergency utility contact list
Keeping trades coordinated
Excavate with reference to the survey, protect exposed services, and stop for redesign or diversion if reality contradicts the drawing. Keep photo records of exposed utilities for the site file.
Where time and cost usually escalate
Strike risk, emergency repairs, diversion lead times, and idle plant after a hit dominate cost far more than the survey fee. Late surveys that force redesign of foundations or drainage are the next largest shock. Rate intent: /groundworks-costs — this page is not a price list.
Stage overview
| Stage | Typical activity | Groundworks implication |
|---|---|---|
| Records | Utility plans / desktop search | Do not treat as complete |
| Detection | CAT/GPR and marking | Marks guide; tolerances apply |
| Confirm | Trial holes at conflicts | Expose before full machine dig |
| Dig | Permit, hand dig near services | Stop and escalate on surprises |
Where this sequence is commonly used
- Foundation dig on urban plots
- Drainage trenches across unknown laterals
- Enabling packages before peak excavation
Frequently asked questions
Is a CAT scan enough on its own?
Often not. Record plans, GPR where appropriate, and trial holes at conflicts give a stronger picture. Follow the project specification.
Does Mainline carry out the utility survey?
Usually you commission a specialist survey. We excavate against it and can coordinate trial holes as part of groundworks.
What if we find an unmarked service?
Stop mechanical dig, protect the service, identify the owner where possible, and escalate before continuing.
Why is the guides utility survey page a consolidate candidate?
To avoid two thin method pages. Prefer this site-preparation URL for method ownership; the guides URL stays until any redirect is approved separately.
Does a clear survey mean we can dig full machine everywhere?
No. Marks have tolerance. Hand dig or careful exposure near indicated services remains standard practice.
How This Issue Is Normally Diagnosed and Repaired
Follow the typical path from problem identification through to resolution:
We provide these services across the UK, including
Get a Free Quote
Contact us for a no-obligation quote or to discuss your project. We'll advise on the best approach and provide clear pricing.
Get an Accurate QuotePlanning dig? Commission a utility survey, then send the pack with your drawings for a groundworks quote.
Utility survey before digging FAQ
Is a CAT scan enough on its own?
Often not. Record plans, GPR where appropriate, and trial holes at conflicts give a stronger picture. Follow the project specification.
Does Mainline carry out the utility survey?
Usually you commission a specialist survey. We excavate against it and can coordinate trial holes as part of groundworks.
What if we find an unmarked service?
Stop mechanical dig, protect the service, identify the owner where possible, and escalate before continuing.
Why is the guides utility survey page a consolidate candidate?
To avoid two thin method pages. Prefer this site-preparation URL for method ownership; the guides URL stays until any redirect is approved separately.
Does a clear survey mean we can dig full machine everywhere?
No. Marks have tolerance. Hand dig or careful exposure near indicated services remains standard practice.
Need project guidance?
Share your site details and priorities. We will outline a practical scope, likely timeline, and next steps.