29 CFR 1926.651: Specific excavation requirements

Question 1

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. ABefore employees enter the excavation, because a hazardous atmosphere could reasonably be expected and the depth is greater than 4 feet
2. BOnce at the end of the shift, after backfilling is complete
3. COnly when the trench is deeper than 12 feet
4. DOnly after an employee reports symptoms of dizziness while working in the trench

Question 2

A crew is excavating a utility trench for a new water service. The excavation is expected to cross the area where a buried gas line may run. The competent person called the gas utility, but the utility says it cannot send a locator for 3 days, and no state or local law requires a longer response period. What may the employer do?

1. AStop all work until the utility locates the line, because the employer may never proceed without a utility locate
2. BProceed with caution, provided detection equipment or other acceptable means are used to locate the utility installations
3. CProceed with normal excavation methods, because the 24-hour period has passed and the utility is responsible for the delay
4. DProceed only after the employer estimates the line location from old as-built drawings, with no further detection needed

Question 3

A crew is installing a storm sewer in a trench. Overnight rain left water accumulating, and the foreman has a sump pump running to hold the water level down so the crew can re-enter. The foreman says the pump will "take care of itself" and assigns no one to watch it. Midmorning, the pump's discharge hose kinks and the pump stops without anyone noticing while four workers are in the trench. Which statement best identifies what the standard required that would have addressed this situation?

1. AThe pump only had to be checked by a competent person at the start of the shift, since inspection is required only when the water is first removed.
2. BA safety harness and lifeline was the only permitted precaution, because water removal equipment cannot be relied on to control accumulating water.
3. CNothing further was required, because the pump was installed before employees re-entered the trench.
4. DA competent person had to monitor the water removal equipment and its operation to ensure it was working properly, since the pump was the control keeping water from accumulating.

Question 4

After a thunderstorm overnight, a crew returns to a 7-foot-deep utility trench. Before anyone enters, the competent person walks the trench and finds fresh cracking along the top of one wall and water seeping from the face. The foreman says the trench was inspected yesterday morning and the crew is behind schedule, so two laborers should begin setting pipe while the competent person goes to inspect another site. What does the standard require in this situation?

1. AWork may proceed because the trench was inspected the previous day and the daily inspection requirement is already satisfied
2. BThe competent person may allow the laborers to enter if they work quickly, as long as an inspection is repeated at the end of the shift
3. COnly the laborers closest to the cracked wall must be removed, and the rest of the crew may continue working in the trench
4. DEmployees must be kept out of the hazardous area until the necessary precautions have been taken to ensure their safety

Question 5

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