NEBOSH CC Excavation & Ground Work Hazards 2 — Questions and Answers
Question 1: Which colour cable sheath is typically associated with electricity supply cables in the UK?
- Black (Correct answer)
- Red
- Yellow
- Blue
Correct answer: Black
Electricity supply cables in the UK are typically black or sometimes grey. Being aware of cable colours helps identify services when excavating, though all services should be treated as live until proven otherwise.
Question 2: What is the safe digging zone recommended around buried services when hand digging?
- 0.5 metres either side of the marked position (Correct answer)
- 1 metre either side of the marked position
- Directly over the marked line only
- 2 metres either side of the marked position
Correct answer: 0.5 metres either side of the marked position
When excavating near buried services, hand digging should be used within 0.5 metres either side of the marked service position. This reduces the risk of striking cables or pipes.
Question 3: What is 'battering back' in the context of excavation safety?
- Cutting the sides of an excavation at a safe angle to prevent collapse (Correct answer)
- Installing horizontal timber boards
- Using hydraulic props to support excavation sides
- Compacting the bottom of an excavation
Correct answer: Cutting the sides of an excavation at a safe angle to prevent collapse
Battering back means cutting the sides of an excavation at a safe angle (slope) so they are self-supporting and less likely to collapse. The required angle depends on soil type, groundwater and other factors.
Question 4: Which document should be used to plan safe working in an excavation?
- Method statement and risk assessment (Correct answer)
- Site diary
- Delivery schedule
- Tool inventory
Correct answer: Method statement and risk assessment
A method statement and risk assessment must be prepared before excavation work begins. These documents outline the safe system of work, identify hazards and specify control measures including shoring methods and emergency procedures.
Question 5: What hazard does water in an excavation present beyond the obvious drowning risk?
- Increased likelihood of side collapse and soil instability (Correct answer)
- Improved ground conditions for digging
- Reduced need for shoring
- Better visibility of underground services
Correct answer: Increased likelihood of side collapse and soil instability
Water in an excavation weakens the surrounding soil, increasing the risk of side collapse. Saturated ground is heavier and loses cohesion, making already unstable sides even more dangerous.
Question 6: How often should excavations be inspected under CDM 2015?
- At the start of each shift, after any event that may affect stability, and after accidental collapse (Correct answer)
- Once per week
- Only when a problem is suspected
- Once per day regardless of conditions
Correct answer: At the start of each shift, after any event that may affect stability, and after accidental collapse
Under CDM 2015, excavations must be inspected at the start of each shift before work begins, after any event likely to affect stability (such as heavy rain), and after any accidental fall of material.
NEBOSH CC Excavation & Ground Work Hazards 2
Which colour cable sheath is typically associated with electricity supply cables in the UK?