CHST Excavation and Trenching Safety 3

Question 1

Under OSHA 1926.652, what is the maximum allowable slope for Type C soil when using the sloping method of protection?

Accepted Answer

1½H:1V (34 degrees from horizontal)

Answer

1H:1V (45 degrees)

Answer

¾H:1V (53 degrees)

Answer

½H:1V (63 degrees)

Question 2

What is a 'trench shield' (trench box), and what is its primary limitation compared to hydraulic shoring?

Accepted Answer

A structure that protects workers from cave-in material but does NOT prevent the trench wall from collapsing

Answer

A hydraulic system that actively pushes against trench walls to prevent movement

Answer

A sloped excavation reinforced with sheet piling

Answer

A timber cribbing system that prevents soil movement

Question 3

Under OSHA 1926.651(h), how must water accumulation in an excavation be controlled?

Accepted Answer

Water must be removed by pumping or diverting, and work must stop when water accumulates to hazardous levels until the competent person determines it is safe to proceed

Answer

Workers may work in accumulated water as long as they wear rubber boots

Answer

Pumping is required only when water depth exceeds 12 inches

Answer

Standing water is acceptable in Type A soil

Question 4

How often must a competent person inspect excavations under OSHA 1926.651(k)?

Accepted Answer

Daily and after any event that could change conditions, such as rain, freezing temperatures, or vibration from nearby equipment

Answer

Weekly

Answer

Before each work shift only

Answer

Once at the start of the project

Question 5

What is the correct soil classification for a trench in soil that is granular (sand), submerged, and has water freely seeping through it?

Accepted Answer

Type C — the least stable classification

Answer

Type A — cohesive and stable

Answer

Type B — medium stability

Answer

Stable Rock — no classification needed

Question 6

Under OSHA 1926.652(c), what is the key requirement for the design of a timber shoring system used as an excavation protective system?

Accepted Answer

It must be designed by a registered professional engineer or meet the tabulated data in OSHA Appendix C to Subpart P

Answer

Any experienced carpenter may design and install the system without documentation

Answer

Timber shoring must match the design of a manufacturer-certified system

Answer

Timber shoring is only permitted in Type A soil