Excavations and Trenching is the OSHA construction standard, 29 CFR 1926 Subpart P, that requires employers to protect workers from cave-ins and the other hazards of digging below ground. It covers everyone who enters a trench or works at the edge of an excavation, from utility crews laying pipe to foundation contractors.
A cave-in can bury a worker in seconds, and OSHA notes that excavation cave-ins cause serious and often fatal injuries. OSHA runs a National Emphasis Program on trenching and excavation, so inspectors who see an open trench are likely to stop and look at it.
What Is the OSHA Excavation Standard?
Subpart P applies to all open excavations made in the earth's surface, including trenches. It has three sections plus appendices:
- 1926.650 sets the scope and definitions.
- 1926.651 lists specific excavation requirements, from utility location to inspections.
- 1926.652 sets the requirements for protective systems.
- The appendices cover soil classification (Appendix A), sloping and benching (Appendix B), timber shoring (Appendix C) and aluminum hydraulic shoring (Appendix D), among other topics.
Key definitions
- Excavation: any man-made cut, cavity, trench or depression in the earth's surface formed by removing earth.
- Trench: a narrow excavation below the surface, generally deeper than it is wide, with a bottom width of no more than 15 feet.
- Protective system: a method of protecting workers from cave-ins, including support systems, sloping and benching, and shield systems.
- Shield: a structure, often called a trench box, that can withstand cave-in forces and protect the workers inside it.
- Competent person: someone capable of identifying existing and predictable hazards and authorized to take prompt corrective measures.
Who Must Comply?
Any employer covered by the construction standards whose employees work in or near an excavation must comply. That includes general contractors, utility and pipeline contractors, plumbing and sewer contractors, landscapers digging for construction work and municipal crews performing construction.
The standard applies regardless of company size, and there is no minimum project duration. A short, shallow trench for a single service line is still an excavation. OSHA-approved State Plans enforce their own versions of the rule, which must be at least as effective as the federal standard and may be stricter. Many states also have their own one-call or "call before you dig" laws that set notice periods before excavation.
Key Requirements
Protective systems
Under 1926.652(a)(1), each worker in an excavation must be protected from cave-ins by an adequate protective system. There are only two exceptions:
- The excavation is made entirely in stable rock.
- The excavation is less than 5 feet deep and a competent person examines the ground and finds no indication of a potential cave-in.
Employers choose from sloping or benching under 1926.652(b), or support systems, shields and other systems under 1926.652(c). Each has four design options, ranging from the simplest (slope at 1.5 horizontal to 1 vertical, or 34 degrees, without classifying the soil) to manufacturer tabulated data or a design approved by a registered professional engineer. When tabulated data or engineered designs are used, a written copy must be kept at the jobsite while the system is being built.
Under Appendix B, the maximum allowable slopes for excavations less than 20 feet deep are vertical for stable rock, 3/4 to 1 (53 degrees) for Type A soil, 1 to 1 (45 degrees) for Type B and 1.5 to 1 (34 degrees) for Type C. Sloping or benching for excavations deeper than 20 feet must be designed by a registered professional engineer.
Soil classification
When an employer relies on soil type to design sloping or shoring, Appendix A requires a competent person to classify the soil using at least one visual and at least one manual test. Soil is classified as stable rock, Type A, Type B or Type C, from most to least stable. Type A cohesive soil has an unconfined compressive strength of 1.5 tons per square foot or greater, while Type C has 0.5 tons per square foot or less. Soil that is fissured, subject to vibration or previously disturbed cannot be Type A.
Specific excavation requirements in 1926.651
- Underground utilities (b): estimate the location of utilities before opening an excavation and contact utility owners within established local response times. If they do not respond within 24 hours, unless state or local law sets a longer period, or cannot locate the line, the employer may proceed with caution using detection equipment.
- Access and egress (c)(2): trench excavations 4 feet or more deep need a stairway, ladder, ramp or other safe means of exit so that no worker has to travel more than 25 feet laterally to reach it.
- Traffic and loads (d) and (e): workers exposed to vehicle traffic must wear high-visibility vests, and no one may work beneath loads handled by lifting or digging equipment.
- Hazardous atmospheres (g): in excavations deeper than 4 feet where a hazardous atmosphere could exist, test the air before entry. An atmosphere with less than 19.5 percent oxygen is oxygen deficient, and precautions are required when flammable gas exceeds 20 percent of its lower flammable limit. Emergency rescue equipment must be readily available where hazardous atmospheres could exist.
- Water (h): workers may not work in excavations with accumulating water unless adequate precautions, such as water removal monitored by a competent person, are taken.
- Spoil and materials (j)(2): keep excavated material, tools and equipment at least 2 feet from the edge, or use retaining devices.
- Walkways (l): where workers or equipment must cross an excavation, provide walkways, with guardrails where the walkway is 6 feet or more above the lower level.
Daily Inspections
Under 1926.651(k), a competent person must inspect excavations, the adjacent areas and protective systems daily for possible cave-ins, protective system failures, hazardous atmospheres and other hazards. Inspections must be done before work starts, as needed throughout the shift, and after every rainstorm or other event that increases the hazard. They are required only when workers can reasonably be expected to be exposed.
If the competent person finds evidence of a potential cave-in, a failing protective system or a hazardous atmosphere, exposed workers must be removed from the area until the necessary precautions are taken. The competent person must have the authority to do this.
Subpart P does not prescribe an inspection form or retention period, but written daily inspection records are a practical way to show the inspections happened, and many contractors use a trench permit or entry checklist that must be completed before anyone enters.
Common Violations and Penalties
Trenching citations often involve basic failures that are easy to see from the street:
- Workers in trenches 5 feet or deeper with no sloping, shoring or trench box.
- Spoil piles placed right at the edge of the trench.
- No ladder or ramp in trenches 4 feet or deeper, or exits more than 25 feet away.
- No competent person inspection, or a competent person without authority to stop work.
- Trench boxes used outside the manufacturer's tabulated data, with no copy on site.
- Digging without locating underground utilities.
OSHA civil penalties are adjusted for inflation each year. For penalties assessed after January 15, 2026, the maximum is $16,550 per serious violation and $165,514 per willful or repeated violation. See OSHA's penalties page for current amounts.
How to Comply: Step by Step
- Call before you dig. Notify the one-call center and utility owners and wait for marks or the required response time.
- Designate a competent person. Make sure they are trained in soil classification and protective systems and have authority to stop work.
- Classify the soil. Perform visual and manual tests, or assume Type C and slope at 1.5 to 1.
- Select and document the protective system. Keep tabulated data or the engineer's design at the jobsite.
- Set up the site. Place spoil at least 2 feet back, provide ladders or ramps within 25 feet, and protect against traffic and water.
- Test the atmosphere. Where hazardous atmospheres are possible in excavations deeper than 4 feet, test before entry and as needed.
- Inspect daily and after rain. Record the results and remove workers if hazards are found.
- Brief the crew. Cover the day's hazards in a toolbox talk before entry.
How SMS360 Helps
SMS360's Work Permits module helps teams control trench entry. Supervisors can use digital permits and checklists to confirm that utilities were located, soil was classified, a protective system is in place and the competent person has completed the daily inspection before anyone enters. Permits can be completed and approved on a mobile device at the trench, and the records are stored centrally for audits and OSHA inspections.
Issues found during inspections can be assigned as corrective actions and tracked to closure, giving safety managers a clear view of open trenching hazards across projects.
Frequently Asked Questions
How deep can a trench be before shoring is required?
OSHA requires a protective system for excavations 5 feet or deeper unless the excavation is made entirely in stable rock. Excavations less than 5 feet deep also need protection if a competent person finds any indication of a potential cave-in. Sloping or benching for excavations deeper than 20 feet must be designed by a registered professional engineer.
When is a ladder required in a trench?
Trench excavations 4 feet or more deep must have a stairway, ladder, ramp or other safe means of exit. It must be located so that workers travel no more than 25 feet laterally to reach it, per 1926.651(c)(2).
How far back must spoil piles be from a trench?
Excavated material, tools and equipment must be kept at least 2 feet from the edge of the excavation, or held back by retaining devices, or both. This keeps loose material from falling or rolling into the trench and reduces the load on the trench walls.
Who can inspect a trench?
A competent person must perform the daily inspection. Under Subpart P, that person must be able to identify existing and predictable hazards and must have the authority to take prompt corrective action, including removing workers from the excavation. Read the full protective system rules on OSHA's 1926.652 page.
