Trenches 5 feet or deeper need cave-in protection: apply OSHA’s slope, shore or shield rule to conduit and cable work

OSHA says trench collapses pose the greatest risk to workers in excavations, requires a protective system for trenches 5 feet deep or more and an engineer-designed one at 20 feet or more, and requires a competent person to inspect trenches and protective systems daily and as conditions change before work begins.

Source facts

OSHA’s trenching and excavation page says trench collapses, or cave-ins, pose the greatest risk to workers’ lives, and lists sloping or benching trench walls, shoring them with supports, or shielding them with trench boxes as the ways to prevent cave-ins. It also says employers should ensure a safe way to enter and exit, keep materials away from the edge, look for standing water or atmospheric hazards, and never let anyone enter a trench that has not been properly inspected, citing 29 CFR 1926.650 through 1926.652.

OSHA’s Working Safely in Trenches QuickCard says trenches 5 feet deep or greater require a protective system, and those 20 feet deep or greater require one designed by a registered professional engineer. It says OSHA standards require trenches and protective systems to be inspected daily and as conditions change by a competent person before work begins.

A 2022 OSHA alert says trench collapses are more likely than other excavation-related incidents to result in worker fatalities, and that it only takes seconds to become buried in thousands of pounds of soil.

Applicability

Use this for any trench that employees enter, including short conduit runs. Michigan employers follow MIOSHA, whose standards must be at least as effective as OSHA’s; check the state rule. Utility locate rules, such as Michigan’s MISS DIG act, apply separately.

DSE recommendation

DSE recommends that no one enter a trench until a competent person has inspected it that day and cave-in protection, a safe exit and clear edges are in place. Plan trench depth and the protective system at the design stage, keep spoil and equipment back from the edge, and stop work for water or changing soil until the trench is inspected again.

Verification

Record the competent person’s daily inspection for each open trench, photograph the protective system and exit in place, and spot-check that crews can name the competent person on site.

Official references

OSHA — Trenching and Excavation. OSHA — Working Safely in Trenches QuickCard (OSHA 3243). OSHA — Trench Collapses Can Be Deadly alert (OSHA 3971, 2022). Reviewed October 19, 2026.