Excavations and Electrical Safety Flashcards

What hazard does standing water in an excavation present on a construction site?

Answer: Risk of drowning, destabilisation of excavation walls, and concealment of hazards on the floor

Standing water in an excavation can drown a worker who falls in, soften the soil causing wall collapse, and conceal sharp objects, cables, or voids on the floor. Water must be pumped out before workers enter.

What is the safe current level that can typically cause ventricular fibrillation (heart stopping) in a human?

Answer: As little as 50 milliamps (0.05 A) passing through the chest

Current as low as 50 milliamps passing through the body across the chest can cause ventricular fibrillation. Even 10 milliamps causes painful muscle contractions. This is why low voltage equipment and RCDs are so important on construction sites.

What must be done before a worker enters a deep excavation in Ireland?

Answer: Inspect it for stability, test for hazardous gases if appropriate, ensure safe access and egress, and have a rescue plan

Before entry into a deep excavation, a competent person must inspect for stability, test the atmosphere for gas accumulation (especially in confined-space-like conditions), provide proper access/egress ladders, and have an emergency rescue plan.

What is a CAT scanner used for on a construction site?

Answer: To detect the location of buried utilities including electricity cables, water pipes, and gas mains

A Cable Avoidance Tool (CAT) detects buried services by picking up electromagnetic signals from live cables and induced signals from other services. It is used before and during excavation to avoid striking buried utilities.

Why must electrical equipment on a construction site be regularly inspected and tested?

Answer: Because construction sites expose equipment to damage, moisture, and harsh conditions that increase fault risk rapidly

Construction site conditions — mechanical damage, moisture, dust, chemicals — degrade electrical equipment rapidly. Regular inspection and portable appliance testing (PAT) detects faults before they cause fires or fatal shocks.

What is the purpose of the safety colour coding of excavation support equipment (e.g., orange or yellow barriers)?

Answer: To make the excavation hazard highly visible to workers, pedestrians, and plant operators

Brightly coloured barriers around excavations ensure they are visible in all light conditions and can be seen by plant operators whose elevated position may limit ground-level visibility. High visibility reduces the risk of vehicles falling in.