Excavation, Trenching & Shoring FAQ

29 CFR 1926 Subpart P is OSHA's excavation standard for construction. It sets requirements for soil classification, protective systems (sloping, benching, shoring, and shielding), safe access and egress, spoil placement, and the daily inspection duties of the Competent Person.

OSHA requires that only trained and authorized personnel design protective systems and that a Competent Person, capable of identifying hazards and authorized to take corrective action, be designated for every excavation site. Employers are responsible for training workers on the hazards of the work they perform. Our Safety Training and Competent Person courses map directly to these requirements.

Non-compliance can result in significant OSHA fines per violation, stop-work orders, and in serious cases criminal referral if a fatality results from a willful violation. Trenching is consistently one of OSHA's most-cited and most fatal construction hazards, and enforcement has intensified in recent years.

Federal OSHA enforces 29 CFR 1926 Subpart P in most states, but roughly half the states run their own OSHA-approved state plans, which must be at least as protective as the federal rules and sometimes add requirements on top. Confirm your state plan's specifics if you're in one.

No. Unlike confined space entry, OSHA's excavation standard doesn't require a written permit for each dig. Instead it requires a Competent Person to evaluate soil and site conditions, select an appropriate protective system, and conduct daily inspections before and during the work.

Stable Rock, Type A, Type B, and Type C, in order from most to least stable:

• Stable Rock — solid mineral material that can be excavated with vertical sides and remain intact
• Type A — the most stable soil, such as clay
• Type B — moderately stable soil
• Type C — the least stable, including granular soils and soil near vibration or previously disturbed ground

The designated Competent Person, using at least one visual test and one manual analysis test (such as a plasticity or dry strength test), classifies the soil type present. This classification then determines which protective systems, and what maximum slope angles, are allowed. Our Competent Person course covers both test methods in detail.

Sloping cuts back the trench wall at an angle away from the excavation, rather than keeping the walls vertical. The maximum allowable slope depends on soil type; Type A soil allows a steeper slope than Type C. Sloping is a valid protective system on its own when there's enough room on site, but many urban or congested sites don't have space for it and require shoring or shielding instead.

Benching cuts the trench wall into a series of horizontal steps, or benches, rather than one continuous slope. Like sloping, the allowable bench dimensions depend on soil type, and benching is not permitted in Type C soil because that soil isn't stable enough to hold a vertical step.

Shoring is a support system, typically hydraulic or timber, installed to prevent trench walls from collapsing. Hydraulic shoring uses aluminum or steel supports under hydraulic pressure and is the most common modern method because it's fast to install and doesn't require workers to enter the trench to place it. Timber shoring uses wood supports and is still used in some conditions, particularly deep or irregular excavations.

A trench shield, or trench box, doesn't prevent a cave-in the way shoring does; it protects workers by containing the collapse if one occurs. Shields are typically steel or aluminum structures that workers perform their work inside of, and unlike shoring, they can often be pulled along the trench as work progresses rather than reinstalled at every section.

Yes. Most protective systems are designed using tabulated data supplied by the manufacturer of the shoring or shielding equipment, which spells out safe configurations for given soil types and depths. A registered professional engineer's design is only required for excavations 20 feet or deeper, or for non-standard conditions the tabulated data doesn't cover.

The Competent Person must inspect the excavation, adjacent areas, and protective systems daily before work begins, after every rainstorm or other hazard-increasing event, and whenever there's an indication of a possible cave-in, protective system failure, or other hazardous condition. Any hazard found must be corrected immediately, and if necessary, workers must be removed from the hazardous area until it's corrected.

A Competent Person is capable of identifying existing and predictable excavation hazards and has the authority to take prompt corrective action, including stopping work. Responsibilities typically include classifying soil, selecting and verifying protective systems, conducting daily inspections, and overseeing the site's written excavation safety program.

OSHA doesn't set a fixed limit on the number of sites, but the Competent Person must be able to actually perform the required daily inspections and be available to respond to hazards at each site they're responsible for. Spreading one Competent Person too thin across sites they can't adequately inspect doesn't meet the standard's intent.

The employer. OSHA requires legally mandated safety training, including excavation and Competent Person training, to be provided at no cost to employees.