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

For Type C soil, the least stable classification, OSHA requires a maximum slope of 1½H:1V (1.5 feet horizontal for every 1 foot vertical), which equals approximately 34 degrees from horizontal.

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 trench shield (trench box) protects workers by shielding them from falling cave-in material. Unlike hydraulic shoring, it does not apply pressure to the trench walls and does not prevent the trench wall from collapsing outside the box.

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

OSHA 1926.651(h) requires that surface water or water run-off be controlled, that workers not work in accumulated water unless adequate precautions are taken, and that all water control measures be directed by the competent person.

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

OSHA 1926.651(k)(1) requires a competent person to inspect excavations prior to each work shift, after rainstorms or other hazard-increasing events, and as needed throughout the shift.

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

Submerged granular soil with free water seepage meets the definition of Type C soil, the least stable classification requiring the most conservative protective system.

CHST - Construction Health and Safety Technician Practice Test

CHST - Construction Health and Safety Technician Practice Test

CHST Excavation and Trenching Safety 3