CITB Specialists Excavation and Groundwork Safety

Question 1

Before a specialist contractor begins excavation work, what must be done to identify underground services?

Accepted Answer

Obtain service plans from utility companies, carry out a CAT and Genny survey, and use safe digging practices

Answer

Before any excavation, the contractor must obtain up-to-date plans from all utility companies, then verify locations using a Cable Avoidance Tool (CAT) and Signal Generator (Genny). Within 500mm of a detected service, only hand digging or vacuum excavation is permitted. HSG47 provides detailed guidance on safe digging practices.

Question 2

At what depth must an unsupported excavation in granular soil generally be considered as requiring engineered support under UK guidance?

Accepted Answer

No specific depth; a risk assessment must determine the need for support in all cases

Answer

There is no fixed depth at which support automatically becomes mandatory. The need for support depends on soil type, ground conditions, water table, surcharge loads, vibration, and weather. A competent person must assess each excavation individually. However, as a practical guide, most excavations over 1.2m in depth will need some form of support.

Question 3

How often must a specialist excavation be inspected by a competent person under the Construction (Design and Management) Regulations 2015?

Accepted Answer

At the start of each shift before work commences, and after any event likely to have affected stability

Answer

CDM 2015 requires that excavations are inspected by a competent person at the start of every shift before anyone enters, and after any event likely to have affected stability (heavy rain, adjacent loading, vibration from plant). The results must be recorded in a written report kept on site.

Question 4

What is the primary purpose of installing trench sheets and walers in a specialist deep excavation?

Accepted Answer

To prevent collapse of the excavation sides and protect workers from being buried

Answer

Trench sheets (or trench sheeting) driven into the ground and held in place by walers (horizontal beams) and struts form a temporary support system that prevents the sides of the excavation from collapsing inward. This is critical — trench collapse is one of the leading causes of death in excavation work.

Question 5

A specialist groundwork supervisor notices that spoil from an excavation has been placed at the edge of the trench. What is the hazard and the correct action?

Accepted Answer

The weight of the spoil surcharges the trench sides, increasing collapse risk — it must be moved back at least 1 metre from the edge

Answer

Spoil heaps placed near the edge of an excavation impose additional surcharge loading on the ground, significantly increasing the risk of side collapse. As a minimum, spoil must be placed at least 1 metre from the edge of the excavation, though the exact distance may need to be greater depending on depth and soil conditions.

CITB HS&E Specialists Practice Test

CITB HS&E Specialists Practice Test

CITB Specialists Excavation and Groundwork Safety