CPCS Working Near Services & Site Hazards 1 — Questions and Answers
Question 1: Before excavating or operating plant near underground services, what must be done?
- Obtain service drawings, use CAT scanning, and establish exclusion zones around identified services (Correct answer)
- Only use CAT scanning — drawings are not reliable
- Start carefully and stop if anything is struck
- Underground services are the main contractor's responsibility only
Correct answer: Obtain service drawings, use CAT scanning, and establish exclusion zones around identified services
Before any excavation near underground services, drawings must be obtained, a CAT (cable avoidance tool) scan performed to locate services, and exclusion zones established around identified services before plant moves.
Question 2: What colour represents a gas pipe in UK underground service identification?
- Yellow (Correct answer)
- Blue
- Red
- Black
Correct answer: Yellow
Gas pipes are identified by yellow in the UK underground services colour coding system. Operators must know the standard colours to identify services correctly when they are exposed.
Question 3: What should an operator do immediately if underground plant strikes a gas pipe?
- Stop the plant, evacuate the area, call the gas emergency number (0800 111 999), and keep people away (Correct answer)
- Continue working and report at the end of the day
- Attempt to identify the pipe type before taking action
- Cover the pipe and inform the site manager only
Correct answer: Stop the plant, evacuate the area, call the gas emergency number (0800 111 999), and keep people away
If a gas pipe is struck, work must stop immediately, the area evacuated, the national gas emergency number (0800 111 999) called, and no ignition sources brought near the site. These actions can prevent an explosion.
Question 4: What does a CAT scan detect and what are its limitations?
- It detects metallic and live electrical cables but may miss non-metallic pipes — must be used alongside service drawings (Correct answer)
- CAT scanning detects all underground utilities without exception
- CAT scanning replaces the need for service drawings
- It detects only gas pipes and electrical cables
Correct answer: It detects metallic and live electrical cables but may miss non-metallic pipes — must be used alongside service drawings
A CAT (cable avoidance tool) detects metallic and live electrical cables but cannot reliably detect non-metallic pipes (e.g. plastic gas pipes). It must always be used alongside drawings and followed by careful manual trial holes.
Question 5: What colour represents electrical services (high voltage) in the UK underground colour coding?
- Red (Correct answer)
- Yellow
- Blue
- Green
Correct answer: Red
High voltage electrical services are identified by red in the UK underground colour coding system. Operators must recognise this colour to identify electrical hazards when services are exposed.
Question 6: What is an exclusion zone in the context of working near overhead power lines?
- A safe distance zone around overhead lines within which plant must not pass without authorisation (Correct answer)
- A zone only relevant to cranes over 50 tonnes
- A zone that can be entered with the site manager's verbal permission
- An exclusion zone is only required for 11 kV and above
Correct answer: A safe distance zone around overhead lines within which plant must not pass without authorisation
An exclusion zone around overhead power lines defines the minimum distance plant must keep from the lines. The zone prevents flashover (electricity arcing to nearby conductive objects), which can be fatal.
CPCS Working Near Services & Site Hazards 1
Before excavating or operating plant near underground services, what must be done?