Trenching and excavation safety

The 5-foot trigger, and its two exceptions

1926.652(a)(1): each employee in an excavation shall be protected from cave-ins by an adequate protective system designed in accordance with paragraph (b) or (c), except when:

• the excavation is made entirely in stable rock; or
• the excavation is less than 5 feet (1.52 m) deep and examination of the ground by a competent person provides no indication of a potential cave-in.

The second exception has two halves and they are joined by “and”. Depth alone does not exempt anything — a competent person has to look and reach a conclusion. Four feet eleven inches in wet, previously disturbed soil is protected or it is a violation.

1926.652(a)(2) adds the design duty: protective systems shall have the capacity to resist without failure all loads intended or reasonably expected to be applied or transmitted to the system.

Four ways to design the protection

Sloping and benching (paragraph b) and support, shield and other systems (paragraph c) each offer four options, and they are alternatives — you pick one, you do not blend them.

Two paperwork rules follow the options and get missed. Where tabulated data is used, at least one copy identifying the registered professional engineer who approved the data shall be maintained at the jobsite during construction of the protective system. And if the competent person cannot assure that material or equipment is able to support the intended loads, it is removed from service and evaluated and approved by a registered professional engineer before it goes back.

The 4-foot rules: egress and atmosphere

Different number, different duty. A stairway, ladder, ramp or other safe means of egress shall be located in trench excavations that are 4 feet (1.22 m) or more in depth, so as to require no more than 25 feet (7.62 m) of lateral travel for employees.

And where an oxygen deficiency or a hazardous atmosphere exists or could reasonably be expected to exist — such as excavations in landfill areas, or near stored hazardous substances — the atmosphere shall be tested before employees enter excavations greater than 4 feet in depth.

The spoil rule is smaller and more often broken: employees shall be protected from excavated or other materials or equipment that could pose a hazard by falling or rolling into the excavation, by placing and keeping such materials or equipment at least 2 feet from the edge, by retaining devices, or by both.

When the atmosphere test comes back bad, you are no longer only in Subpart P. See permit-required confined spaces.

Egress

The daily inspection

1926.651(k): daily inspections of excavations, the adjacent areas and the protective systems shall be made by a competent person for evidence of a situation that could result in possible cave-ins, indications of failure of protective systems, hazardous atmospheres or other hazardous conditions. The inspection shall be conducted prior to the start of work and as needed throughout the shift.

“As needed” has an unmissable trigger: after every rainstorm or other hazard-increasing occurrence. A trench that was fine on Friday is a different trench on Monday.

The competent person here is the standard’s own definition — capable of identifying the hazards, and authorised to take prompt corrective measures. Not the person who happens to be free. That distinction is worked through in competent person under OSHA, and the daily walk itself sits on the construction safety checklist.