Excavations and Trenching practice questions for the CHST exam

A crew is excavating a 6-foot-deep utility trench on a site that was previously a landfill. The competent person asks when the atmosphere in the trench must be tested. According to the standard, when is testing required?

1. A.Before employees enter the excavation, because a hazardous atmosphere could reasonably be expected and the depth is greater than 4 feet
2. B.Once at the end of the shift, after backfilling is complete
3. C.Only when the trench is deeper than 12 feet
4. D.Only after an employee reports symptoms of dizziness while working in the trench

A crew is installing a trench shield chosen from the manufacturer's tabulated data. On day two, the foreman finds that the trench will be deeper than the maximum depth in the manufacturer's data for that shield. The competent person has inspected the excavation and believes the shield can handle the extra depth. A supervisor suggests getting a verbal okay from the manufacturer's technical line and putting it in the daily log. Which action complies with the standard?

1. A.Proceed, because the competent person's on-site inspection and judgment can authorize exceeding the manufacturer's depth limit
2. B.Proceed after the manufacturer's technical line gives verbal approval that is recorded in the daily log
3. C.Do not exceed the listed depth limit unless the manufacturer issues specific written approval, and keep that approval at the jobsite during construction of the protective system
4. D.Proceed if the shield is rated for the soil type, because only deviations from soil classification limits require manufacturer approval

After a heavy overnight rainstorm, a competent person inspects a trench before the crew starts work. She finds water pooled along one wall and fresh soil sloughing from it. Two workers already in the trench are laying pipe, and the crew lead says the morning inspection is done, so work should continue and be rechecked at the end of the shift. What does the standard require?

1. A.Let the two workers finish the pipe section, then take precautions at the end of the shift, since the daily inspection has been completed.
2. B.Keep the workers in place but have one of them watch the wall and warn the others if more soil falls.
3. C.Leave the crew in the trench and keep the spoil pile at least 2 feet from the edge, which addresses the sloughing.
4. D.Remove the exposed employees from the trench until the necessary precautions have been taken to ensure their safety.