Buried Services Questions
CITB buried services questions test whether you know how services are found, marked and dug around safely, and the right answer usually assumes a service is there until proved otherwise.
Most questions put you on a dig: you turn up marker tape, uncover a pipe you cannot identify, or need to break out a road surface near a cable, and you choose the next step. Our questions are built on HSE's guidance HSG47, Avoiding danger from underground services, with a few from HSE's HSG150. A common trap: a plan that shows no services does not mean the ground is clear. HSG47 says to assume services are present unless you have been shown otherwise. Take the timed quiz below, then read the 10 sample questions further down, each with a worked explanation. Practise buried services before your CITB Operatives Test or Specialist test, and check yourself with a CITB Operatives mock test.
Start the buried services quiz
The timed buried services quiz draws from our full buried services set and explains every answer. The quiz is free: 1 quiz every 7 days without an account, or 30 a day with a free account. A paid plan gives you unlimited quizzes.
Free practice quiz
Buried Services practice quiz (timed)
- questions
- 20
- questions
- minutes
- 30
- minutes
- to pass (90%)
- 18
- to pass (90%)
- Answers and explanations are shown at the end, with every question to review.
- A fresh set of questions every attempt, drawn across CITB's five core knowledge areas.
- About 90 seconds a question, against about 54 in the real test, so there is time to think.
- Every answer comes with a worked explanation.
Ready when you are
Find a quiet 30 minutes. The clock starts when you press start, and you see your score the moment you submit.
How do CITB buried services questions usually ask it?
Buried services questions usually put you in or beside an excavation, with marker tape, an unknown pipe or a damaged service, and ask what you do next.
| Question pattern | What it looks like, in our words | What the right answer usually does |
|---|---|---|
| Marker tape and tiles | Digging turns up warning tape or tiles, and you choose what they tell you and what happens to them | Treats them as a sign a service is near, without relying on them for its exact position, and puts them back above the service when the hole is filled |
| What a damaged service does | You pick the typical hazard from hitting a cable, a gas pipe, a water main or a sewer | Matches the service to its harm: burns from an arcing cable, fire or explosion from gas, a jet of water or flooding from a main, and raw sewage from a sewer |
| Finding and exposing a service | You have plans, a locator and a surface to break out, and you choose how to find the service and dig down to it | Uses the plans and a locator, then hand digs trial holes to confirm the position. HSG47 says plans alone are not enough to locate services |
Which law and guidance are buried services questions based on?
Our buried services questions are built mainly on HSE's HSG47, Avoiding danger from underground services, with HSE's HSG150 for general site practice when a service is found.
| Law or guidance | What the questions take from it |
|---|---|
| HSE HSG47, Avoiding danger from underground services (third edition, 2014) | The three parts of a safe system of work (planning, detecting and marking services, safe digging), what plans and locators can and cannot tell you, how to identify an uncovered service, what to do if one is damaged, and backfilling |
| HSE HSG150, Health and safety in construction (third edition, 2006) | Using cable avoidance tools, known as CATs, and stopping work when an unidentified service turns up |
| Construction (Design and Management) Regulations 2015, regulation 25 | The legal duty under the guidance: construction work that could create a risk from an underground service must not go ahead until suitable and sufficient steps have been taken to prevent that risk, so far as is reasonably practicable |
| Electricity at Work Regulations 1989, regulation 14 | The conditions that must all be met before anyone works on or near a live conductor |
| Pipelines Safety Regulations 1996, regulation 15 | No one may damage a pipeline in a way that could put people in danger |
The trench you dig to reach a service has dangers of its own, and Confined Spaces and Excavations Questions covers how excavations are kept safe.
Buried services sample questions with worked explanations
Here are 10 buried services practice questions, each with the answer and a worked explanation.
Sample question 1 · Buried & Underground Services
What does HSG47 say about relying on service plans alone before starting work?
- Plans are sufficient if they were issued by the owner within the last twelve months
- Plans are sufficient provided they are printed in colour and drawn to a stated scale
- Plans are sufficient where the site is a green field rather than a congested street
- Plans are not sufficient on their own and are the basis for a thorough site surveyCorrect answer
Why D: HSG47 paragraph 39 states plainly that plans alone are not sufficient to identify and locate services before starting work, and that they provide basic information on which to base a thorough site survey. Paragraph 41 lists why: plans may not be drawn accurately to scale, kerb lines move, surfaces are re-graded, and cables get moved without the owner knowing.
Sample question 2 · Buried & Underground Services
You need to mark the line of a located service on a grassed area. What should you use?
- Steel pins driven firmly into the line of the service so they are not knocked out
- Long steel spikes at both ends, with string run between them to show the route
- Nothing physical, because ground markings will be lost before the dig starts
- Wooden pegs, kept to one side of the service rather than driven in above itCorrect answer
Why D: HSG47 paragraph 97 says to mark the line with waterproof crayon, chalk or paint on paved surfaces, or with wooden pegs in grassed or unsurfaced areas, preferably to one side of the service. It adds that steel pins, spikes or long pegs which could damage services laid at shallow depth should not be used. Paragraph 127 repeats the point for stakes and posts.
Sample question 3 · Buried & Underground Services
HSG47 recommends a particular technique for the final exposure of a service. What is it?
- Mechanical excavation on the slowest setting, kept under constant supervision
- Horizontal digging, because the force applied to hand tools is controlled betterCorrect answer
- Vertical digging, because it gives the shortest route straight down to the top of the run
- Vacuum excavation only, because hand tools must never be used near any service
Why B: HSG47 paragraph 110 recommends final exposure of the service by horizontal digging, because the force applied to hand tools can be controlled more effectively that way. The same paragraph says to use insulated tools when hand digging near electric cables.
Sample question 4 · Buried & Underground Services
Why does HSG47 warn against working bare-chested near buried electricity cables or gas pipes?
- The employer cannot check that the right protective clothing is being worn
- Burns are made more severe, and even ordinary work clothing reduces themCorrect answer
- Loose skin contact makes an electric shock more likely to stop the heart
- Bare skin picks up more contamination from the soil in a service trench
Why B: HSG47 paragraph 119 says burns are the main injuries resulting from damage to live electrical cables or from fire or explosion following a gas leak, and that in many cases burns are made more severe by the injured person working bare-chested. Even ordinary work clothing can greatly reduce the severity, though man-made fibres such as nylon may melt and stick to the skin.
Sample question 5 · Buried & Underground Services
What does HSG47 say about encasing underground services in concrete?
- Services may be encased in concrete where the ground is soft and support is needed
- Services should never be buried or encased in concrete, as breaking it out is dangerousCorrect answer
- Services should be encased in concrete wherever they cross beneath a busy roadway
- Services may be encased in concrete provided the position is recorded on the plans
Why B: The box at HSG47 paragraph 134 says services should not be buried or encased in concrete as excavating close to them is dangerous, and that using mechanical means to break up concrete can damage cables or pipes, which if live will likely mean anyone present is injured. Paragraph 140 calls cables encased in concrete bad practice, while admitting it is not uncommon.
Sample question 6 · Buried & Underground Services
Why does HSG47 tell you to use a signal generator with a locator wherever possible?
- It allows the locator to be used by someone who has not been trained on it
- It measures the depth of the service without any need to dig a trial hole
- It works through concrete, which ordinary detection methods cannot do
- It significantly increases the accuracy of locating and tracing the serviceCorrect answer
Why D: HSG47 paragraph 85 says in bold that use of signal generators will significantly increase the accuracy of the service location. Paragraph 90 adds that a locator may not distinguish between cables or pipes running close together and may show them as a single signal, and that if two are one above the other the lower one may not be detected, so use signal generators whenever possible.
Sample question 7 · Buried & Underground Services
What does HSG47 expect a designer to do about underground services?
- Leave the question to the principal contractor, who controls the site once work starts
- Mark the services on the ground before the contractor is appointed to the project
- Obtain the plans and then take no further part, as design is complete before the dig
- Reduce or design out the risks, then tell those doing the work what risks remainCorrect answer
Why D: HSG47 paragraph 51 says designers have a duty to reduce or design out the risks arising from damage to underground services, and having reduced them so far as is reasonably practicable, to provide information about the risks that remain to those doing the work, in most cases on the working drawings. Paragraph 53 notes re-siting services away from the work is often a reasonably practicable way of avoiding the risk.
Sample question 8 · Buried & Underground Services
Under the Electricity at Work Regulations 1989, when may work be carried out on or near a live uninsulated conductor?
- Whenever insulated tools and arc-rated protective clothing have been provided
- Only where it is unreasonable for it to be dead, reasonable to work live, and safeCorrect answer
- Whenever the work is urgent and the supervisor has recorded that in the site diary
- Whenever the worker holds a valid competence card for the type of work involved
Why B: Regulation 14 of the Electricity at Work Regulations 1989 permits work on or near a live uninsulated conductor only where all three conditions are met: it is unreasonable in all the circumstances for it to be dead, it is reasonable in all the circumstances to be at work on or near it while live, and suitable precautions including where necessary suitable protective equipment are taken to prevent injury. All three, not any one.
Sample question 9 · Buried & Underground Services
What does HSG47 warn can follow from false readings or signals during detection?
- A delay to the programme, which is the main reason surveys are skipped
- A requirement to repeat the desktop study before excavation can restart
- Inaccurate information in the plan of work and a false sense of securityCorrect answer
- Damage to the locator, which then has to be recalibrated by the supplier before reuse
Why C: HSG47 paragraph 84 says anyone selecting detection tools and survey methods must understand the range of methods and tools and their limitations, and in particular be aware of the potential for false readings or signals in certain techniques, as these may lead to inaccurate information being included in the plan of work and, in turn, lead to a false sense of security.
Sample question 10 · Buried & Underground Services
The plans turn out to be wrong: a service is found well away from its recorded position. What should happen?
- Note it on the site copy of the drawing, which is normally filed at project end
- Nothing, because the plans were supplied as a guide and carry a disclaimer
- Move the service back to the recorded line shown on the plan before the excavation is filled in
- Tell the owner, preferably before backfilling, so they can amend their recordsCorrect answer
Why D: HSG47 paragraph 135 says that if the plans have proved inaccurate, for example a service is found well away from its recorded position, or if the work changes the path or depth of a service, inform the service owners or operators, preferably before the excavation is backfilled, and they should amend their records accordingly.
Which buried services answers catch people out?
The traps are answers that trust the kit or the markers too far: expecting a locator to find a plastic pipe, reusing warning tape and marking the line with steel pins.
A cable locator will usually not find a plastic gas or water pipe. HSG47 says locators, with the possible exception of ground-probing radar, do not detect non-metallic services unless a metal tracer wire was laid with the pipe, a tracing rod or small transmitter is pushed along it, or RFID markers are fitted. It adds that few plastic pipes were laid with tracer wires in the past.
Warning tiles and tape go back in their original place above the services when you backfill. If digging showed they were in the wrong place, they go back above the service they belong to. HSG47 also says warning tape must not be used for anything else, such as guarding an excavation, and must not be thrown into the hole during backfilling.
Mark the line of a service on grass or bare ground with wooden pegs, preferably to one side of it. HSG47 says steel pins, spikes or long pegs should not be used, because they could damage a service laid at shallow depth. On paved surfaces the line is marked with waterproof crayon, chalk or paint.
Where does buried services sit in the CITB test?
Buried services is part of the core knowledge you practise for the CITB Operatives test. The Specialist tests include the core questions too, so the same knowledge counts there.
Buried services FAQs
Can a cable locator find plastic pipes?
Usually not. HSG47 says locators, with the possible exception of ground-probing radar, do not detect plastic pipes unless a metal tracer wire was laid with the pipe, a tracing rod or small transmitter is pushed along it, or RFID markers are fitted.
Are these the real CITB test questions?
No. These are practice questions written for this site, each tied to the law or HSE guidance it tests; CITB does not publish its test questions.