CITB Specialists Excavation and Groundwork Safety 2

Question 1

What does the 'angle of repose' refer to in specialist excavation work?

Accepted Answer

The steepest angle at which soil or loose material can be stacked without sliding

Answer

The angle of repose is the maximum angle at which soil or granular material remains stable without slipping. It varies by soil type — sand may be 30-35 degrees, while clay can be steeper when dry but much shallower when wet. Understanding this is critical for determining whether battering back the sides is sufficient or if sheet piling is needed.

Question 2

A specialist contractor encounters groundwater ingress during deep excavation. What is the most appropriate response?

Accepted Answer

Implement a dewatering system (wellpoint or sump pumping) and assess the effect on surrounding structures and services

Answer

Groundwater ingress requires controlled dewatering using appropriate methods (wellpoint dewatering, sump pumps). Crucially, the effect of lowering the water table on adjacent structures, services, and contaminated land must be assessed, as dewatering can cause settlement. Discharge of pumped water must comply with Environment Agency requirements.

Question 3

What type of access and egress must be provided for specialist workers in excavations deeper than 1.2 metres?

Accepted Answer

A secured ladder extending at least 1 metre above the excavation edge, positioned within reasonable reach of all work positions

Answer

Safe access and egress must be provided, typically by a secured ladder extending at least 1 metre above the top of the excavation. Ladders must be positioned so that workers do not have to travel more than a reasonable distance (typically 25 metres) laterally along the excavation to reach one. Steps cut into soil are not acceptable as they undermine the trench wall.

Question 4

Under UK environmental regulations, what must a specialist contractor do if contaminated soil is discovered during excavation?

Accepted Answer

Stop work, isolate the area, test the material, and dispose of it at a licensed facility in accordance with waste regulations

Answer

Contaminated soil is classified as controlled waste. The contractor must stop work, prevent further spread, characterise the contamination through testing, and arrange disposal at a suitably licensed facility. Duty of care waste transfer notes must be completed. Mixing contaminated soil with clean soil is illegal under the Environmental Protection Act 1990.

Question 5

What is the purpose of a 'permit to dig' system used by specialist groundwork contractors?

Accepted Answer

To formally confirm that underground services have been located and marked, safe digging methods agreed, and specific precautions are in place before digging begins

Answer

A permit to dig is a formal management control document that confirms service drawings have been checked, detection equipment has been used, services have been marked on the ground, safe digging methods are specified (hand dig zones), and all relevant precautions are in place. It must be signed by the supervisor and reviewed if conditions change.

CITB HS&E Specialists Practice Test

CITB HS&E Specialists Practice Test

CITB Specialists Excavation and Groundwork Safety 2