Excavation scope and definitions

This subpart applies to all open excavations made in the earth’s surface, and it explicitly includes trenches. See 1926.650(a).

• That means any man-made cut, cavity, trench, or depression formed by earth removal is covered.
• If your work involves digging below the earth’s surface, plan to follow the rules in Subpart P from the start. See also the general Subpart P overview at 1926.

An "excavation" is any man-made cut, cavity, trench, or depression in an earth surface formed by earth removal, and a "trench" is a narrow excavation (in relation to its length) where the depth is generally greater than the width and the bottom width is not greater than 15 feet (4.6 m). See 1926.650(b).

• If forms or structures reduce the measured distance at the bottom to 15 feet or less, the excavation is also considered a trench.
• Use these definitions to determine which protective-system requirements apply for a given dig.

A "competent person" is someone capable of identifying existing and predictable hazards around the excavation and who has the authority to take prompt corrective measures to eliminate them. See 1926.650(b).

• This person must be able to recognize hazards like unstable soil, water accumulation, or equipment-related dangers and stop work or require changes when necessary.
• Employers must designate and empower a competent person for excavation jobs to comply with Subpart P.

A "protective system" is any method that protects employees from cave-ins, falling material, or collapse of adjacent structures; it includes sloping, benching, support systems, shield systems (trench boxes), and other systems providing necessary protection. See 1926.650(b).

• Choose the system based on soil, depth, and job conditions.
• The competent person must determine which protective system is appropriate for the situation.

A "cave-in" is the sudden separation and movement of a mass of soil or rock into an excavation in sufficient quantity to entrap, bury, injure, or immobilize a person; it also includes loss of soil from under a trench shield or support that causes sudden movement. See 1926.650(b).

• Because cave-ins are defined by sudden movement and potential to injure, protective systems must be designed to prevent them.
• Competent persons must monitor conditions that can lead to cave-ins (e.g., weather, vibrations, nearby loads).

A "shield" is a structure designed to withstand the forces of a cave-in and protect employees inside it; shields used in trenches are commonly called "trench boxes" or "trench shields." See 1926.650(b).

• Shields may be portable or job-built and can be premanufactured.
• When using a trench box or shield, ensure it is sized and installed so it resists soil pressures for the excavation depth and conditions.

"Sloping" means cutting the sides of an excavation to incline away from the excavation to prevent cave-ins, and "benching" means excavating the sides to form horizontal levels or steps; both are protective methods to prevent cave-ins. See 1926.650(b).

• The required angle or step configuration depends on soil type, exposure conditions, and surcharge loads.
• A competent person must determine whether sloping or benching is appropriate for the site conditions.

"Stable rock" is natural solid mineral material that can be excavated with vertical sides and remain intact while exposed; when rock is secured by bolts or engineered protective systems it may be considered stable even if it initially appears unstable. See 1926.650(b).

• If an excavation is entirely in stable rock, vertical sides may be acceptable without additional protective systems.
• A competent person or a registered professional engineer should verify rock stability before omitting protective systems.

"Tabulated data" are tables and charts approved by a registered professional engineer that can be used to design and construct a protective system. See 1926.650(b).

• Use tabulated data when the protective system and site conditions match the assumptions used by the engineer who approved the tables.
• If site conditions differ, the competent person must consult a registered professional engineer for site-specific designs.

A "registered professional engineer" is someone registered in the state where the work is performed; such an engineer can design protective systems, approve tabulated data, and sign designs for manufactured protective systems used in interstate commerce. See 1926.650(b).

• When protective systems require engineering (e.g., deep excavations, unique soil conditions), use designs or tabulated data approved by a registered professional engineer.
• A professional engineer registered in any state may approve designs for manufactured systems used across state lines.

A "support system" provides support to adjacent structures, underground installations, or excavation sides (e.g., underpinning, bracing, shoring), while "shoring" refers specifically to structures (metal, mechanical, timber) designed to support excavation sides and "sheeting" are the members that retain the earth and are supported by the shoring. See 1926.650(b).

• Use the correct term when documenting protective measures: shoring and sheeting are components of a support system.
• Designs for support systems should follow accepted engineering practices or tabulated data approved by a registered professional engineer.

"Uprights" are vertical members placed in contact with the earth in a trench shoring system; "wales" are horizontal members placed parallel to the excavation face that bear against uprights; and "cross braces" are horizontal members installed perpendicular to the sides that bear against uprights or wales. See 1926.650(b).

• Proper installation and spacing of these components are critical to maintain shoring integrity.
• A competent person or engineer should verify that the shoring system is appropriate for soil conditions and trench depth.

A "kickout" is the accidental release or failure of a cross brace in a shoring system. See 1926.650(b).

• Kickouts can immediately reduce the protective capability of a shoring system and create cave-in hazards.
• Competent persons must inspect shoring, secure cross braces, and remove employees from the trench if a kickout or other failure occurs.

"Failure" means the breakage, displacement, or permanent deformation of a structural member or connection that reduces its structural integrity and supportive capabilities. See 1926.650(b).

• Any sign of failure in shoring, bracing, or shield components requires immediate corrective action and likely removal of employees from the excavation until repairs are made.
• Regular inspections by the competent person help detect failures early.

A "hazardous atmosphere" is one that is explosive, flammable, poisonous, oxygen-deficient, corrosive, oxidizing, irritating, toxic, or otherwise harmful and may cause death, illness, or injury. See 1926.650(b).

• Before entry, a competent person must evaluate trenches for hazardous atmospheres and provide testing and ventilation or respiratory protection as needed.
• Confined-space-like conditions (e.g., deep trenches) can trap gases, so treat atmospheres seriously during excavation work.

A "structural ramp" is built of steel or wood (usually for vehicle access), while ramps made of soil or rock are not considered structural ramps. See 1926.650(b).

• Use structural ramps when you need predictable, engineered access for equipment or vehicles.
• Soil/rock ramps may be acceptable for foot access but can change stability and must be evaluated by the competent person.

If forms or other structures in an excavation reduce the distance from the forms or structure to the excavation side to 15 feet (4.6 m) or less (measured at the bottom), OSHA considers that excavation a "trench" and it must meet trench protections. See 1926.650(b).

• Treat such excavations with the same protective-system requirements as trenches, including shoring, shielding, or sloping as determined by the competent person.
• This rule prevents work-arounds where structural inserts could otherwise circumvent trench protections.

OSHA means that any method that reliably prevents cave-ins or protects employees from falling material—whether support (shoring/underpinning), sloping, benching, shields (trench boxes), or other engineered systems—qualifies as a protective system. See 1926.650(b) and the general Subpart P overview at 1926.

• The competent person selects among these options based on soil, depth, adjacent loads, and other site conditions.
• If the chosen method is not listed explicitly, it still qualifies as a protective system if it provides necessary protection and is designed by an engineer when required.

Protective systems used in trenches must be designed to prevent cave-ins and protect employees, and they include sloping, benching, support systems, shield systems, and other approved methods; specific design, installation, and inspection requirements are in 1926.652. See 1926.652(c).

• Follow the design requirements and tables in 1926.652 when using tabulated data or manufactured systems.
• The competent person must inspect protective systems daily and after events that could affect stability (e.g., rainstorms, nearby heavy equipment operations).

Job-built shields are permitted when they are designed by a registered professional engineer and constructed to withstand the forces expected from a cave-in; requirements for job-built shields are in 1926.652(c)(3).

• Job-built shields must be engineered, properly constructed, and inspected by the competent person.
• If job-built shields are not engineered, do not use them—use premanufactured shields or engineer the design first.

OSHA allows premanufactured shields when they are designed and manufactured to withstand expected cave-in forces and are used according to the manufacturer’s specifications; see 1926.652(c)(4).

• Always follow the manufacturer’s instructions for spacing, placement, and maximum trench depth.
• The competent person must ensure the premanufactured shield is appropriate for the soil and trench conditions before entry.

"Benching" is a protective method that forms one or a series of horizontal levels or steps with vertical or near-vertical faces between levels specifically to protect employees from cave-ins; it is a designed protective system, not just random steps. See 1926.650(b).

• Proper benching dimensions depend on soil type and must be determined by a competent person or a registered professional engineer for complex conditions.
• Do not assume a stepped cut provides adequate protection unless it meets benching design criteria.

A competent person must inspect excavations, adjacent areas, and protective systems daily and as needed throughout the shift, especially after any hazard-increasing event (e.g., rain, vibration, overhead loads) to ensure continued safety. See 1926.650(b) and protective system requirements in 1926.652.

• Inspections must verify that protective systems remain intact and that no signs of failure exist.
• If hazards are found, the competent person must remove employees and correct the hazard immediately.

"Faces or sides" are the vertical or inclined earth surfaces formed as a result of excavation work; "sides" is used interchangeably with "faces." See 1926.650(b).

• Proper identification of faces/sides helps in planning protective systems and placing barriers to prevent falls and material roll-ins.
• Competent persons should evaluate face conditions (e.g., overhangs, water seepage) when selecting protection.

A "bell-bottom pier hole" is a shaft or footing excavation whose bottom is made larger than the cross section above to create a belled shape; it is a type of shaft or footing excavation and not automatically treated as a trench unless it meets the trench definition criteria. See 1926.650(b).

• Protective systems and inspection requirements still apply based on depth, soil, and hazard potential.
• Consult a competent person or engineer to determine necessary protections for such excavations.

"Shoring" is a structure (metal hydraulic, mechanical, or timber) that supports excavation sides to prevent cave-ins; shoring is required whenever the competent person determines that sloping or benching alone will not provide adequate protection for employees. See 1926.650(b) and protective system rules at 1926.652.

• Shoring must be designed, installed, and inspected for the specific trench depth and soil conditions.
• If shoring components show damage or failure, remove employees until corrected.

A "ramp" is an inclined walking or working surface used to gain access and can be made of earth or structural materials, while a "structural ramp" is specifically built of steel or wood (usually for vehicle access); soil or rock ramps are not structural. See 1926.650(b).

• Choose ramp type based on expected loads (foot traffic vs. equipment) and inspect ramps for stability as part of the competent person’s duties.
• Structural ramps require design consideration for loads and safe slope; non-structural ramps must be evaluated for stability and erosion risk.

A "trench shield" is a type of shield (often called a trench box) that protects workers inside from cave-ins; it may be moved along as work progresses provided movement follows manufacturer instructions and safe procedures. See 1926.650(b) and shield requirements at 1926.652.

• Moving trench shields requires checking for underlying soil support, avoiding sudden shifts, and ensuring no workers are under unsupported soil.
• The competent person must supervise movement and verify the shield’s suitability for the next location.

"Faces or sides" protection focuses on preventing cave-ins and protecting workers from soil collapse, while "falling object" protection guards against materials or tools falling into the excavation from above; both are part of protective systems under Subpart P. See 1926.650(b) and related provisions in 1926.652.

• Implement measures such as benching/shoring/sloping or trench shields for sides/faces.
• Use toe-boards, barricades, material placement controls, or canopies to protect against falling objects.

"Other systems" are any protective methods not specifically named (support, sloping, benching, shield) that nevertheless provide the necessary protection from cave-ins or falling material; such systems must be as effective as those specifically listed and, when required, be designed by a registered professional engineer. See 1926.650(b).

• If you use a novel or hybrid protective approach, document its design basis and ensure a competent person and/or engineer approve it.
• The key requirement is effectiveness in protecting employees—not the label of the system.

"Sheeting" are the members of a shoring system that retain earth in position and are supported by other shoring members; when uprights are placed so closely together that they contact or interconnect, they may be considered sheeting rather than individual uprights. See 1926.650(b).

• Recognizing when uprights function as sheeting matters for installation technique and inspection.
• Ensure sheeting is appropriate for soil pressure and is checked by the competent person.

Protective system selection must account for surcharge loads (extra weight near the excavation such as vehicles, stockpiled materials, or buildings) and adjacent structures because these increase soil pressure and cave-in risk; the competent person and, when necessary, a registered professional engineer must evaluate and design protection accordingly. See 1926.650(b).

• Placing heavy equipment or material too close to the edge can change required slopes or shoring strength.
• If adjacent structures could collapse into the excavation, use engineered underpinning or special support systems.