CSCS Buried & Underground Services Questions
Cable avoidance tools, permits and safe digging practice.
Buried & Underground Services — practice questions (untimed, instant feedback)
- 1 questions · pass mark 90%
- Untimed practice — you see the correct answer immediately after each question.
- Some questions need more than one answer — these are clearly marked.
All 1 Buried & Underground Services questions and answers
These are the same 1 questions as the practice test above, written out with the correct answer and the reasoning behind it. Read them through when you want to revise rather than test yourself.
1. While digging you uncover a run of coloured marker tape. What does it mean?
Answer: A buried service lies below and you must dig on with care
- A) The trench now needs shoring
- B) The ground is contaminated and you need RPE
- C) Human remains are buried and you must tell your supervisor
- D) A buried service lies below and you must dig on with care (correct answer)
Why: Marker tape warns of a buried service just below — carry on digging carefully.
What this topic covers in the CSCS test
Almost every site has gas mains, electricity cables, water pipes, sewers or telecoms ducts running under it. Striking one can kill through arc flash, fire or explosion. HSE guidance HSG47 sets out how to avoid that, and most test questions on this topic come straight from it.
- The three parts of a safe system of work: plan, locate and identify, then excavate safely
- Service plans from the owners, and why plans alone are never proof
- Cable locators (CAT and signal generator) and trial holes
- Safe digging: hand tools, digging alongside rather than above, the 500 mm rule
- Identifying an exposed service, and what to assume when you cannot be sure
- Marker tape, warning tiles and marker posts, and putting them back after backfilling
- What to do when a service is struck, including why the driver stays in the cab
Key facts worth memorising
- Three elements of a safe system
- HSG47 breaks the job into planning the work, locating and identifying buried services, then safe excavation, in that order.
- Assume everything is live
- HSG47 says to assume all services are live until disconnected and proven safe at the point of work.
- The 500 mm margin
- Where practicable, hand-held power tools should only be used 500 mm or more away from the indicated line of a service buried in or below a hard surface.
- Dig alongside, not above
- Excavate alongside the service rather than directly above it, expose it finally by horizontal digging, and use insulated tools when hand digging near electric cables.
- Black plastic means electricity
- Assume any black plastic service is a live electricity cable, treat any iron or steel pipe as a gas pipe, and if in any doubt treat a service as an electricity cable or gas pipe.
- Plans are a starting point
- HSE states plainly that plans alone are not sufficient, because they are not always to scale, depths change when ground is re-graded, and connections are often unmarked.
What people get wrong
The colour of the pipe or duct tells you what the service is.
A national colour coding system exists for modern utility apparatus, but HSG47 warns that older and non-utility services may not follow it, colours look different under poor light, and a duct could hold any service.
The plan shows nothing there, so it is safe to dig.
Plans give you the basis for a survey, not permission to dig. No surface indication of a service does not mean there is no service.
Once you have scanned with a CAT you can carry on digging.
HSG47 says to use locators frequently and repeatedly during the work, because location gets more accurate as cover is removed.
If the machine strikes a cable, get down and look at the damage.
Drivers stay in the cab, because climbing down can electrocute them. Isolate and secure the area, and let nobody near until the owner has made the cable safe.
Answering these questions in the test
These questions reward the slow, cautious answer. If an option involves pressing on, guessing a service from its colour or trusting a drawing, it is wrong. Look for the answer that stops, checks with a locator, digs by hand or asks the supervisor. Marker tape is a specific trap: it means a service lies just below and you carry on with extra care, not that the ground is contaminated or the trench needs shoring.
Sources
Written from the following. Where a figure could not be verified against one of these, it has been left out rather than approximated — our sources and methodology explains how we date and re-check them. Spotted something wrong? Report an error and we will fix it.
Topics that come up alongside buried & underground services
Ready for the real thing?
When you are scoring 90% or better here, take a timed 50-question mock under exam conditions, then book your CITB HS&E test.