NEBOSH CC Excavation & Ground Work Hazards 4 — Questions and Answers
Question 1: What is the primary purpose of edge protection around an excavation?
- To prevent people and vehicles from falling into the excavation (Correct answer)
- To mark the boundary of the excavation for planning purposes
- To stop soil from eroding at the edges
- To anchor the shoring system
Correct answer: To prevent people and vehicles from falling into the excavation
Edge protection such as barriers, guard rails or close-boarded fencing prevents people (especially pedestrians) and vehicles from accidentally falling into an open excavation. It also alerts people to the presence of the hazard.
Question 2: Which underground service is typically identified by a yellow or yellow-striped pipe in the UK?
- Gas (Correct answer)
- Electricity
- Water
- Telecommunications
Correct answer: Gas
Gas pipes in the UK are typically yellow or have yellow stripes. Identifying the correct service by colour helps workers determine the type of hazard they may encounter during excavation.
Question 3: What is the recommended first action when an uncharted underground service is discovered during excavation?
- Stop work, secure the area, and contact the relevant utility company (Correct answer)
- Continue work with extra care
- Try to identify the service type and cut it safely
- Report it to the HSE immediately
Correct answer: Stop work, secure the area, and contact the relevant utility company
If an uncharted service is discovered, work must stop immediately and the area must be secured. The relevant utility company should be contacted to identify and make safe the service before work resumes.
Question 4: What does 'striking a service' mean in excavation terminology?
- Hitting an underground utility cable or pipe with a tool or machine (Correct answer)
- Finding the location of an underground service
- Installing a new underground service
- Inspecting an underground service
Correct answer: Hitting an underground utility cable or pipe with a tool or machine
'Striking a service' means accidentally hitting an underground utility (gas pipe, electrical cable, water main, etc.) with excavation tools or plant. This can cause explosions, electrocution, flooding or fire.
Question 5: What is the main risk when excavating in contaminated land?
- Exposure to harmful substances including toxic gases, chemicals and biological hazards (Correct answer)
- Increased ground instability
- Difficulty in using standard shoring equipment
- Damage to underground services
Correct answer: Exposure to harmful substances including toxic gases, chemicals and biological hazards
Excavating contaminated land exposes workers to toxic gases (such as methane and hydrogen sulphide), chemicals, asbestos and biological hazards. Air monitoring and appropriate PPE including respiratory protection are essential.
Question 6: What is the purpose of a 'walkway' or bridge over an excavation?
- To allow safe pedestrian crossing without the risk of falling in (Correct answer)
- To support the weight of heavy plant over the excavation
- To act as a shoring system at the top of the excavation
- To measure the width of the trench
Correct answer: To allow safe pedestrian crossing without the risk of falling in
A properly constructed walkway or bridge with guard rails allows workers and pedestrians to cross an open excavation safely, eliminating the risk of falls into the trench.
NEBOSH CC Excavation & Ground Work Hazards 4
What is the primary purpose of edge protection around an excavation?