Plumbing is the trade where the safety numbers are depths and distances rather than a single trigger height, and where getting one of them wrong is how a routine dig becomes a fatality. Excavations need a protective system at 5 feet under 1926.652(a)(1) — unless the excavation is entirely in stable rock, or it is under 5 feet AND a competent person has examined the ground and found no indication of a potential cave-in. Both exceptions matter and both get quoted loosely. A trench needs a stairway, ladder or ramp within 25 feet of lateral travel once it is 4 feet deep under 1926.651(c)(2), and that same 4-foot depth is where atmospheric testing kicks in wherever a hazardous atmosphere could reasonably be expected, which on sewer work it always can.
Hot work is the other number set. A fire watch is required whenever appreciable combustible material sits closer than 35 feet to the point of operation. The duration is where template writers slip: general industry says the watch is maintained at least a half hour after the work stops (1910.252(a)(2)(iii)(B)), but the construction rule (1926.352(e)) gives no number at all — it says only "a sufficient period of time". This checklist states both, and treats thirty minutes as the defensible floor rather than pretending construction has a stated interval it does not have.
The document itself is a daily verification list, not a hazard analysis. That distinction matters because contractors are often told to produce "a safety document" and end up with a risk assessment that nobody reads on the morning it would help. A risk assessment scores hazards on a matrix once per project; a method statement writes out the safe-work sequence for one job. This is the short list a crew works before the first shovel — and it has a stop-work gate, so marking the trench item as an issue prints "Stop work — do not start" at the very top of the export, above the company block, rather than burying it on page two next to the tick that said the truck had a fire extinguisher.