STSC Excavation and Trenching Safety 2

Question 1

What is a 'competent person' required to do regarding excavation inspections under OSHA Subpart P?

Accepted Answer

Inspect before the start of work, as needed during the shift, and after rain or other events that could increase hazard

Answer

Inspect the excavation once per week

Answer

Inspect only when requested by workers or the project manager

Answer

Inspect at the start and end of each day only

Question 2

When is atmospheric testing required before workers enter an excavation?

Accepted Answer

When the excavation may reasonably be expected to have an atmosphere containing harmful levels of gases, vapors, or oxygen deficiency

Answer

Only for excavations near industrial facilities

Answer

When the excavation is 20 feet or more deep

Answer

Only for excavations in confined space locations (indoors)

Question 3

A trench is being excavated in Type B soil. The trench is 10 feet deep. What is the required horizontal setback (slope) for each side of the trench?

Accepted Answer

5 feet from the base on each side (1:1 ratio)

Answer

3.75 feet from the base on each side (3/4:1 ratio)

Answer

7.5 feet from the base on each side (3/2:1 ratio)

Answer

No setback required with proper shoring

Question 4

What is the OSHA definition of a 'trench' as distinct from a general 'excavation'?

Accepted Answer

An excavation that is narrower than it is deep, with a maximum width of 15 feet at the bottom

Answer

Any underground opening more than 2 feet wide

Answer

Any excavation made by mechanical equipment

Answer

An excavation specifically for utility installation

Question 5

A trench protection system uses a hydraulic trench shield (trench box). Where must workers be positioned relative to the shield when working in the trench?

Accepted Answer

Workers must remain inside the protective shield at all times during excavation operations

Answer

Workers may work anywhere in the trench as long as they are supervised

Answer

Workers must stay within 2 feet of the shield at all times

Answer

Workers may exit the shield to place bedding material at the trench bottom

Question 6

After a significant rainfall, the competent person inspects a trench in Type A soil and finds that water has accumulated in the bottom of the trench and the walls show some cracking. What must happen?

Accepted Answer

The trench must be reclassified as at most Type C, water must be controlled, and the trench re-evaluated before workers re-enter

Answer

Workers may enter if they wear rubber boots

Answer

Workers may enter immediately if the water depth is less than 6 inches

Answer

Type A classification can be maintained if additional shoring is added while workers are in the trench