OSHA construction excavations study guide
Subpart P of OSHA's construction rules (29 CFR 1926.650 to 1926.652 and Appendices A to F) covers excavations and trenches. This guide sets out what the rule text states on utilities, access and egress, atmospheres, water, inspections, protective systems and soil classification. Every point links to the rule text it comes from, with the exact words quoted. It is an independent study aid, not OSHA training.
Scope and definitions
Subpart P applies to all open excavations made in the earth's surface, and trenches count as excavations.
“This subpart applies to all open excavations made in the earth's surface. Excavations are defined to include trenches.”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
An excavation is any man-made cut, cavity, trench or depression in an earth surface, formed by earth removal.
“Excavation means any man-made cut, cavity, trench, or depression in an earth surface, formed by earth removal.”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
A trench is a narrow excavation (in relation to its length) made below the surface of the ground. In general it is deeper than it is wide, and its width measured at the bottom is not greater than 15 feet.
“Trench (Trench excavation) means a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width, but the width of a trench (measured at the bottom) is not greater than 15 feet (4.6 m).”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
A wider excavation also counts as a trench if forms or other structures inside it bring the distance from the form or structure to the side of the excavation down to 15 feet or less, measured at the bottom.
“If forms or other structures are installed or constructed in an excavation so as to reduce the dimension measured from the forms or structure to the side of the excavation to 15 feet (4.6 m) or less (measured at the bottom of the excavation), the excavation is also considered to be a trench.”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
A cave-in is soil or rock separating from the side of an excavation, or soil lost from under a trench shield or support system, and moving suddenly into the excavation in enough quantity to entrap, bury, or injure and immobilize a person.
“Cave-in means the separation of a mass of soil or rock material from the side of an excavation, or the loss of soil from under a trench shield or support system, and its sudden movement into the excavation, either by falling or sliding, in sufficient quantity so that it could entrap, bury, or otherwise injure and immobilize a person.”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
A competent person must be able to identify existing and predictable hazards in the surroundings, or working conditions that are unsanitary, hazardous or dangerous to employees, and must also have the authority to take prompt corrective measures to eliminate them.
“Competent person means one who is capable of identifying existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
A protective system protects employees from cave-ins, from material falling or rolling from a face or into the excavation, and from the collapse of adjacent structures. It includes support systems, sloping and benching systems, shield systems and other systems that give the needed protection.
“Protective system means a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, or from the collapse of adjacent structures. Protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection.”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
Surface encumbrances and underground installations
Surface encumbrances located so as to create a hazard to employees must be removed or supported as necessary.
“All surface encumbrances that are located so as to create a hazard to employees shall be removed or supported, as necessary, to safeguard employees.”
Before an excavation is opened, the estimated location of utility installations (sewer, telephone, fuel, electric, water lines or other underground installations that may reasonably be expected) must be determined.
“The estimated location of utility installations, such as sewer, telephone, fuel, electric, water lines, or any other underground installations that reasonably may be expected to be encountered during excavation work, shall be determined prior to opening an excavation.”
Utility companies or owners must be contacted within established or customary local response times, told about the proposed work and asked to establish the location of their underground installations before actual excavation starts.
“Utility companies or owners shall be contacted within established or customary local response times, advised of the proposed work, and asked to establish the location of the utility underground installations prior to the start of actual excavation.”
If the utility cannot respond within 24 hours (unless state or local law requires a longer period), or cannot establish the exact location, the employer may proceed only with caution and with detection equipment or other acceptable means to locate the installations.
“When utility companies or owners cannot respond to a request to locate underground utility installations within 24 hours (unless a longer period is required by state or local law), or cannot establish the exact location of these installations, the employer may proceed, provided the employer does so with caution, and provided detection equipment or other acceptable means to locate utility installations are used.”
As excavation operations approach the estimated location of underground installations, the exact location must be determined by safe and acceptable means.
“When excavation operations approach the estimated location of underground installations, the exact location of the installations shall be determined by safe and acceptable means.”
While the excavation is open, underground installations must be protected, supported or removed as necessary to safeguard employees.
“While the excavation is open, underground installations shall be protected, supported or removed as necessary to safeguard employees.”
Access and egress
Trench excavations 4 feet or more deep must have a stairway, ladder, ramp or other safe means of egress located so that employees travel no more than 25 feet laterally to reach it.
“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.”
Structural ramps used only by employees must be designed by a competent person. Structural ramps used by equipment must be designed by a competent person qualified in structural design and built to that design.
“Structural ramps that are used solely by employees as a means of access or egress from excavations shall be designed by a competent person. Structural ramps used for access or egress of equipment shall be designed by a competent person qualified in structural design, and shall be constructed in accordance with the design.”
Walkways must be provided where employees or equipment are required or permitted to cross over excavations, with guardrails (meeting 1926.502(b)) where the walkway is 6 feet or more above lower levels.
“Walkways shall be provided where employees or equipment are required or permitted to cross over excavations. Guardrails which comply with § 1926.502(b) shall be provided where walkways are 6 feet (1.8 m) or more above lower levels.”
Traffic, falling loads and mobile equipment
Employees exposed to public vehicular traffic must be given, and must wear, warning vests or other garments marked with or made of reflectorized or high-visibility material.
“Employees exposed to public vehicular traffic shall be provided with, and shall wear, warning vests or other suitable garments marked with or made of reflectorized or high-visibility material.”
No employee may be under loads handled by lifting or digging equipment, and employees must stand away from vehicles being loaded or unloaded to avoid spillage or falling materials. Operators may stay in the cab when the vehicle is equipped under 1926.601(b)(6) to protect the operator during loading and unloading.
“No employee shall be permitted underneath loads handled by lifting or digging equipment. Employees shall be required to stand away from any vehicle being loaded or unloaded to avoid being struck by any spillage or falling materials. Operators may remain in the cabs of vehicles being loaded or unloaded when the vehicles are equipped, in accordance with § 1926.601(b)(6), to provide adequate protection for the operator during loading and unloading operations.”
When mobile equipment works next to or approaches the edge of an excavation and the operator has no clear and direct view of the edge, a warning system such as barricades, hand or mechanical signals, or stop logs must be used.
“When mobile equipment is operated adjacent to an excavation, or when such equipment is required to approach the edge of an excavation, and the operator does not have a clear and direct view of the edge of the excavation, a warning system shall be utilized such as barricades, hand or mechanical signals, or stop logs.”
Hazardous atmospheres
A hazardous atmosphere is one that may cause death, illness or injury because it is explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen deficient, toxic or otherwise harmful.
“Hazardous atmosphere means an atmosphere which by reason of being explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen deficient, toxic, or otherwise harmful, may cause death, illness, or injury.”
29 CFR 1926.650, Scope, application, and definitions applicable to this subpart
Where oxygen deficiency (less than 19.5 percent oxygen) or a hazardous atmosphere exists or could reasonably be expected, such as in landfill areas or near stored hazardous substances, the atmosphere must be tested before employees enter excavations greater than 4 feet deep.
“Where oxygen deficiency (atmospheres containing less than 19.5 percent oxygen) or a hazardous atmosphere exists or could reasonably be expected to exist, such as in excavations in landfill areas or excavations in areas where hazardous substances are stored nearby, the atmospheres in the excavation shall be tested before employees enter excavations greater than 4 feet (1.22 m) in depth.”
Adequate precautions, such as ventilation, must keep employees from exposure to a flammable gas concentration above 20 percent of the gas's lower flammable limit.
“Adequate precaution shall be taken such as providing ventilation, to prevent employee exposure to an atmosphere containing a concentration of a flammable gas in excess of 20 percent of the lower flammable limit of the gas.”
When controls are used to reduce atmospheric contaminants to acceptable levels, testing must be done as often as necessary to make sure the atmosphere stays safe.
“When controls are used that are intended to reduce the level of atmospheric contaminants to acceptable levels, testing shall be conducted as often as necessary to ensure that the atmosphere remains safe.”
Emergency rescue equipment (such as breathing apparatus, a safety harness and line, or a basket stretcher) must be readily available where hazardous atmospheric conditions exist or may reasonably be expected, and attended when in use.
“Emergency rescue equipment, such as breathing apparatus, a safety harness and line, or a basket stretcher, shall be readily available where hazardous atmospheric conditions exist or may reasonably be expected to develop during work in an excavation. This equipment shall be attended when in use.”
Employees entering bell-bottom pier holes or similar deep, confined footing excavations must wear a harness with a lifeline that is separate from any material-handling line and individually attended the whole time they are inside.
“Employees entering bell-bottom pier holes, or other similar deep and confined footing excavations, shall wear a harness with a life-line securely attached to it. The lifeline shall be separate from any line used to handle materials, and shall be individually attended at all times while the employee wearing the lifeline is in the excavation.”
Water, adjacent structures and falling material
Employees may not work in excavations with accumulated or accumulating water unless adequate precautions have been taken to protect them against the hazards of water accumulation.
“Employees shall not work in excavations in which there is accumulated water, or in excavations in which water is accumulating, unless adequate precautions have been taken to protect employees against the hazards posed by water accumulation.”
The precautions needed vary with each situation, but the rule says they could include special support or shield systems against cave-ins, water removal to control the water level, or a safety harness and lifeline.
“The precautions necessary to protect employees adequately vary with each situation, but could include special support or shield systems to protect from cave-ins, water removal to control the level of accumulating water, or use of a safety harness and lifeline.”
If water removal equipment is used to control or prevent water accumulation, a competent person must monitor the equipment and operations to ensure proper operation.
“If water is controlled or prevented from accumulating by the use of water removal equipment, the water removal equipment and operations shall be monitored by a competent person to ensure proper operation.”
Excavations subject to runoff from heavy rains require an inspection by a competent person and compliance with the water accumulation and water removal requirements in 1926.651(h)(1) and (h)(2).
“Excavations subject to runoff from heavy rains will require an inspection by a competent person and compliance with paragraphs (h)(1) and (h)(2) of this section.”
Where excavation endangers the stability of adjoining buildings, walls or other structures, support systems such as shoring, bracing or underpinning must be provided.
“Where the stability of adjoining buildings, walls, or other structures is endangered by excavation operations, support systems such as shoring, bracing, or underpinning shall be provided to ensure the stability of such structures for the protection of employees.”
Employees must be protected from excavated or other materials or equipment that could fall or roll into excavations: by keeping them at least 2 feet from the edge, by retaining devices that prevent them falling or rolling in, or by both if necessary.
“Employees shall be protected from excavated or other materials or equipment that could pose a hazard by falling or rolling into excavations. Protection shall be provided by placing and keeping such materials or equipment at least 2 feet (.61 m) from the edge of excavations, or by the use of retaining devices that are sufficient to prevent materials or equipment from falling or rolling into excavations, or by a combination of both if necessary.”
Inspections by a competent person
A competent person must inspect excavations, adjacent areas and protective systems daily for possible cave-ins, failing protective systems, hazardous atmospheres or other hazardous conditions, before work starts and as needed during the shift.
“Daily inspections of excavations, the adjacent areas, and 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. An inspection shall be conducted by the competent person prior to the start of work and as needed throughout the shift.”
Inspections are also required after every rainstorm or other hazard-increasing occurrence. The inspections are only required when employee exposure can be reasonably anticipated.
“Inspections shall also be made after every rainstorm or other hazard increasing occurrence. These inspections are only required when employee exposure can be reasonably anticipated.”
Where the competent person finds evidence of a situation that could result in a possible cave-in, signs of protective system failure, hazardous atmospheres or other hazardous conditions, exposed employees must be removed from the hazardous area until the necessary precautions have been taken.
“Where the competent person finds evidence of a situation that could result in a possible cave-in, indications of failure of protective systems, hazardous atmospheres, or other hazardous conditions, exposed employees shall be removed from the hazardous area until the necessary precautions have been taken to ensure their safety.”
Protective systems
Each employee in an excavation must be protected from cave-ins by an adequate protective system designed under 1926.652(b) or (c), except in the two cases in the next points.
“Each employee in an excavation shall be protected from cave-ins by an adequate protective system designed in accordance with paragraph (b) or (c) of this section except when:”
The first exception covers excavations made entirely in stable rock.
“Excavations are made entirely in stable rock”
The second exception covers excavations less than 5 feet deep, but only when a competent person examines the ground and finds no indication of a potential cave-in.
“Excavations are less than 5 feet (1.52m) in depth and examination of the ground by a competent person provides no indication of a potential cave-in.”
Protective systems must be able to resist, without failure, all loads intended or reasonably expected to be applied or transmitted to them.
“Protective systems shall have the capacity to resist without failure all loads that are intended or could reasonably be expected to be applied or transmitted to the system.”
Under sloping Option (1), excavations must be sloped no steeper than 1.5 horizontal to 1 vertical (34 degrees measured from the horizontal), unless the employer uses one of the other options in 1926.652(b).
“Excavations shall be sloped at an angle not steeper than one and one-half horizontal to one vertical (34 degrees measured from the horizontal), unless the employer uses one of the other options listed below.”
Option (1) slopes must be excavated to form configurations that follow the slopes shown for Type C soil in Appendix B.
“Slopes specified in paragraph (b)(1)(i) of this section, shall be excavated to form configurations that are in accordance with the slopes shown for Type C soil in appendix B to this subpart.”
Under sloping Option (2), maximum allowable slopes and allowable configurations for sloping and benching systems are determined under the conditions and requirements in Appendices A and B.
“Maximum allowable slopes, and allowable configurations for sloping and benching systems, shall be determined in accordance with the conditions and requirements set forth in appendices A and B to this subpart.”
Sloping and benching systems that do not use Option (1), (2) or (3) of 1926.652(b) must be approved by a registered professional engineer.
“Sloping and benching systems not utilizing Option (1) or Option (2) or Option (3) under paragraph (b) of this section shall be approved by a registered professional engineer.”
Support systems, shield systems or other protective systems drawn from manufacturer's tabulated data must follow all specifications, recommendations and limitations issued or made by the manufacturer.
“Design of support systems, shield systems, or other protective systems that are drawn from manufacturer's tabulated data shall be in accordance with all specifications, recommendations, and limitations issued or made by the manufacturer.”
Deviation from the manufacturer's specifications, recommendations and limitations is allowed only after the manufacturer issues specific written approval.
“Deviation from the specifications, recommendations, and limitations issued or made by the manufacturer shall only be allowed after the manufacturer issues specific written approval.”
Removal of a support system must begin at, and progress from, the bottom of the excavation. Members must be released slowly so as to note any sign of possible failure of the remaining members or possible cave-in of the sides.
“Removal shall begin at, and progress from, the bottom of the excavation. Members shall be released slowly so as to note any indication of possible failure of the remaining members of the structure or possible cave-in of the sides of the excavation.”
Backfilling must progress together with the removal of support systems from excavations.
“Backfilling shall progress together with the removal of support systems from excavations.”
Employees may not be in shields while the shields are being installed, removed or moved vertically.
“Employees shall not be allowed in shields when shields are being installed, removed, or moved vertically.”
Employees must be protected from cave-ins when entering or exiting the areas protected by shields.
“Employees shall be protected from the hazard of cave-ins when entering or exiting the areas protected by shields.”
Soil classification and sloping (Appendices A and B)
Appendix A states that it applies when a sloping or benching system is designed under 1926.652(b)(2), when timber shoring for excavations is designed under Appendix C, and when aluminum hydraulic shoring is designed under Appendix D.
“This appendix applies when a sloping or benching system is designed in accordance with the requirements set forth in § 1926.652(b)(2) as a method of protection for employees from cave-ins. This appendix also applies when timber shoring for excavations is designed as a method of protection from cave-ins in accordance with appendix C to subpart P of part 1926, and when aluminum hydraulic shoring is designed in accordance with appendix D.”
Appendix A also applies when other protective systems are designed and selected from data prepared under 1926.652(c), if use of that data is predicated on the Appendix A soil classification system.
“This appendix also applies if other protective systems are designed and selected for use from data prepared in accordance with the requirements set forth in § 1926.652(c), and the use of the data is predicated on the use of the soil classification system set forth in this appendix.”
The soil classification system ranks soil and rock deposits as Stable Rock, Type A, Type B and Type C, in decreasing order of stability.
“Soil classification system means, for the purpose of this subpart, a method of categorizing soil and rock deposits in a hierarchy of Stable Rock, Type A, Type B, and Type C, in decreasing order of stability.”
The classification of soil and rock deposits must be based on the results of at least one visual and at least one manual analysis. A competent person must conduct these analyses, using the tests described in Appendix A paragraph (d) or other recognized methods of soil classification and testing (such as those adopted by ASTM or the USDA textural classification system).
“The classification of the deposits shall be made based on the results of at least one visual and at least one manual analysis. Such analyses shall be conducted by a competent person using tests described in paragraph (d) below, or in other recognized methods of soil classification and testing such as those adopted by the America Society for Testing Materials, or the U.S. Department of Agriculture textural classification system.”
Type A soils are cohesive soils with an unconfined compressive strength of 1.5 tons per square foot (tsf) or greater, subject to the exclusions in the next point.
“Type A means cohesive soils with an unconfined compressive strength of 1.5 ton per square foot (tsf) (144 kPa) or greater.”
No soil is Type A if it is fissured, subject to vibration from heavy traffic, pile driving or similar effects, previously disturbed, part of a sloped, layered system whose layers dip into the excavation on a slope of 4H:1V or greater, or subject to other factors that would require it to be classified as a less stable material.
“However, no soil is Type A if: (i) The soil is fissured; or (ii) The soil is subject to vibration from heavy traffic, pile driving, or similar effects; or (iii) The soil has been previously disturbed; or (iv) The soil is part of a sloped, layered system where the layers dip into the excavation on a slope of four horizontal to one vertical (4H:1V) or greater; or (v) The material is subject to other factors that would require it to be classified as a less stable material.”
Type C includes cohesive soil with an unconfined compressive strength of 0.5 tsf or less.
“Cohesive soil with an unconfined compressive strength of 0.5 tsf (48 kPa) or less; or”
Type C also includes granular soils such as gravel, sand and loamy sand, and submerged soil or soil from which water is freely seeping.
“Granular soils including gravel, sand, and loamy sand; or (iii) Submerged soil or soil from which water is freely seeping”
A layered system is classified by its weakest layer, but each layer may be classified individually where a more stable layer lies under a less stable layer.
“In a layered system, the system shall be classified in accordance with its weakest layer. However, each layer may be classified individually where a more stable layer lies under a less stable layer.”
Appendix B's requirements apply when the design of sloping and benching protective systems is to be performed under 1926.652(b)(2).
“The requirements of this appendix apply when the design of sloping and benching protective systems is to be performed in accordance with the requirements set forth in § 1926.652(b)(2).”
Under Appendix B, the actual slope must be less steep than the maximum allowable slope when there are signs of distress.
“The actual slope shall be less steep than the maximum allowable slope, when there are signs of distress.”
Under Appendix B, when surcharge loads from stored material or equipment, operating equipment or traffic are present, a competent person must decide how far the actual slope must be reduced below the maximum allowable slope and make sure that reduction is achieved.
“When surcharge loads from stored material or equipment, operating equipment, or traffic are present, a competent person shall determine the degree to which the actual slope must be reduced below the maximum allowable slope, and shall assure that such reduction is achieved.”
Not covered here
We do not summarize Table B-1 and the slope drawings in Appendix B, the timber and aluminum hydraulic shoring tables in Appendices C and D, or the figures in Appendices E and F, because the eCFR copy we checked shows them as images rather than text we can quote. We also leave out the exact amount Appendix B says a slope must be cut back when there are signs of distress, because the fraction does not come through cleanly in that text copy. We only write what an official source states, so study these parts with your certifying program's materials.
Sources
- eCFR: 29 CFR 1926.650, Scope, application, and definitions applicable to this subpart (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.651, Specific excavation requirements (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR 1926.652, Requirements for protective systems (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 29 CFR Part 1926, Subpart P, Appendix A (as of Nov 3, 2026)Checked November 5, 2026
Other OSHA Construction study guides: Introduction to OSHA, Fall protection, Scaffolds, Stairways and ladders, Electrical safety, Personal protective equipment, Health hazards, Hazard communication, Respirable crystalline silica, Welding and cutting, General safety and health