Trench excavation

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## 29 CFR 1926 (OSHA) ## Subpart P-Excavations AUTHORITY: Sec. 107, Contract Worker Hours and Safety Standards Act (Construction Safety Act) (40 U.S.C. 333); Secs. 4, 6, 8, Occupational Safety and Hea1th Act of 1970 (29 U.S.C. 653, 655, 657); Secretary of Labor's Order No. 12-71 (36 FR 8754), 8-76 (41 FR [redacted postal code]), or 9-83 (48 FR [redacted postal code]), as applicable, and 29 CFR part 1911. SOURCE: 54 FR [redacted postal code], Oct. 31, 1989, unless otherwise noted. ## §1926.650 Scope, application, and definitions applicable to this subpart. (a) Scope and application. This subpart applies to all open excavations made in the earth's surface. Excavations are defined to include trenches. ## (b) Definitions applicable to this subpart. Accepted engineering practices means those requirements which are compatible with standards of practice required by a registered professional engineer. Aluminum Hydraulic Shoring means a pre-engineered shoring system comprised of aluminum hydraulic cylinders (crossbraces) used in conjunction with vertical rails (uprights) or horizontal rails (walers). Such system is designed, specifically to support the sidewalls of an excavation and prevent cave-ins. Bell-bottom pier hole means a type of shaft or footing excavation, the bottom of which is made larger than the cross section above to form a belled shape. Benching (Benching system) means a method of protecting employees from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels. 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. Competent person means one who is capable of…

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## 29 CFR 1926 (OSHA) - (iii) 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. - (iv) 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. - (2) Emergency rescue equipment. (i) 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. - (ii) 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. - (h) Protection from hazards associated with water accumulation. (1) 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 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. - (2) 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. - (3) If excavation work interrupts the natural drainage of surface …

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## 29 CFR 1926 (OSHA) Failure means the breakage, displacement, or permanent deformation of a structural member or connection so as to reduce its structural integrity and its supportive capabilities. 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. Kickout means the accidental release or failure of a cross brace. 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. Ramp means an inclined walking or working surface that is used to gain access to one point from another, and is constructed from earth or from structural materials such as steel or wood. Registered Professional Engineer means a person who is registered as a professional engineer in the state where the work is to be performed. However, a professional engineer, registered in any state is deemed to be a 'registered professional engineer' within the meaning of this standard when approving designs for 'manufactured protective systems' or 'tabulated data' to be used in interstate commerce. Sheeting means the members of a shoring system that retain the earth in position and in turn are supported by other members of the shoring system. Shield (Shield system) means a structure that is able to withstand the forces imposed on it by a cavein and thereby protect employees within the structure. Shields can be permanent structures or can be designed to be portable and moved along as work progresses. Additionally, shields can be either premanufactured or job-built in accordance with §1926.652 (c)(3) or (c)(4). Shields used in trenches are usually referred to…

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## OCCUPATIONAL HEALTH AND SAFETY, 2020 - (3) An employer or contractor shall ensure that a temporary protective structure in an excavation more than 3 metres deep is designed and certified as safe by a professional engineer and installed, used, maintained and dismantled in accordance with that design. 31 Dec 2020 c S-15.1 Reg 10 s17-6. ## Protection against cave-in of trenches - 17-7 (1) If a worker is present in a trench that is more than 1.2 metres deep, an employer or contractor shall ensure that the worker is protected from cave-ins or sliding material by: - (a) cutting back the upper portion of the walls of the trench in accordance with subsection 17-4(2); - (b) installing a temporary protective structure; or - (c) a combination of cutting back the walls to the slope specified in subsection 17-4(2) and installing a temporary protective structure that extends at least 300 millimetres above the base of the cut-back. - (2) An employer or contractor shall ensure that a temporary protective structure required by clause (1) (b) or (c) is: - (a) designed and installed using shoring made of number 1 structural grade spruce lumber having the dimensions set out in Table 14 of the Appendix for the type of soil and the depth of the trench or made of material of equivalent or greater strength; or - (b) designed by a professional engineer and constructed, installed, used, maintained and dismantled in accordance with that design. - (3) An employer or contractor shall ensure that a temporary protective structure in a trench more than 6 metres deep in type 1, type 2 or type 3 soil or in a trench more than 4 metres deep in type 4 soil is designed and certified as safe by a professional engineer and installed, used, maintained and dismantled in accordance with that design. - (4) An employer or contractor shall ensure that: - (a) shoring is installed and removed in a manner that protects workers from cave-ins and structural collapses and from being struck …

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- (iv) A registered professional engineer has approved the determination that such excavation work will not pose a hazard to employees. - (3) Sidewalks, pavements, and appurtenant structure shall not be undermined unless a support system or another method of protection is provided to protect employees from the possible collapse of such structures. - (j) Protection of employees from loose rock or soil. (1) Adequate protection shall be provided to protect employees from loose rock or soil that could pose a hazard by falling or rolling from an excavation face. Such protection shall consist of scaling to remove loose material; installation of protective barricades at intervals as necessary on the face to stop and contain falling material; or other means that provide equivalent protection. - (2) 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. - (k) Inspections. (1) 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 shall also be made after every rainstorm or other hazard increasing occurrence. These inspections are only required when employee exposure can be reasonably anticipated. - (2) Where the competent person finds evidence of a situation that could result in a possible cave-in, indications of failure of protective sys…

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## 29 CFR 1926 (OSHA) Support system means a structure such as underpinning, bracing, or shoring, which provides support to an adjacent structure, underground installation, or the sides of an excavation. Tabulated data means tables and charts approved by a registered professional engineer and used to design and construct a protective system. 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). 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. Trench box. See 'Shield.' ## Trench shield. See 'Shield.' Uprights means the vertical members of a trench shoring system placed in contact with the earth and usually positioned so that individual members do not contact each other. Uprights placed so that individual members are closely spaced, in contact with or interconnected to each other, are often called 'sheeting.' Wales means horizontal members of a shoring system placed parallel to the excavation face whose sides bear against the vertical members of the shoring system or earth. ## §1926.651 Specific excavation requirements. - (a) Surface encumbrances. All surface encumbrances that are located so as to create a hazard to employees shall be removed or supported, as necessary, to safeguard employees. - (b) Underground installations. (1) 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. - (2) Utility companies or…

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## OCCUPATIONAL HEALTH AND SAFETY, 2020 S-15.1 REG 10 - (6) If a worker is required to enter a trench, an employer or contractor shall: - (a) install ladders, stairways or ramps to provide a safe means of entrance to and exit from the trench; and - (b) ensure that the ladder, stairway or ramp is located not more than 8 metres from a worker working in the trench. - (7) An employer or contractor shall ensure that workers are instructed in and comply with the requirements of this section. 31 Dec 2020 c S-15.1 Reg 10 s17-7. ## Excavated shafts and tunnels - 17-8 (1) An employer or contractor shall ensure that: - (a) during excavating, the walls of an excavated shaft or tunnel are retained by temporary protective structures that are adequate: - (i) for the type of soil; and - (ii) to prevent collapse or cave-in of the walls of the excavated shaft or tunnel; - (b) during the excavating of an excavated shaft that is 3 metres or more deep or of a tunnel, the walls of the shaft or tunnel are retained by temporary protective structures designed and certified by a professional engineer to be adequate for the protection of workers in the shaft or tunnel and constructed, installed, used, maintained and dismantled in accordance with that design; - (c) a solid or wire mesh fence at least 1 metre high, or other equally effective means of preventing material from falling into an excavated shaft or the surface opening of a tunnel, is provided around that shaft or opening; and - (d) substantial gates that are not less than 1 metre high are installed in every opening in a fence provided pursuant to clause (c) and the gates are kept closed except when being used. - (2) A worker who opens a gate mentioned in clause (1) (d) shall close the gate after the worker no longer has a need to keep the gate open. - (3) An employer or contractor shall provide suitable equipment to keep a tunnel or excavated shaft free from any accumulation of water. 31 Dec 2020 c S-15.1 Reg 10 s17-8. ## Bor…

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- (a) cutting back the walls of the excavation to reduce the height of the remaining vertical walls, if any, to no more than 1.5 metres for 'hard and compact soil' and 'likely to crack or crumble soil', - (b) installing temporary protective structures, or - (c) using a combination of the methods in clauses (a) and (b). 450 (2) Subsection (1) does not apply if a trench is constructed in solid rock throughout the entire trench. ## Cutting back walls - 451 If the walls of an excavation are cut back, an employer must ensure that - (a) if the soil is classified as 'hard and compact soil', the walls are sloped to within 1.5 metres of the bottom of the excavation at an angle of not less than 30 degrees measured from the vertical, - (b) if the soil is classified as 'likely to crack or crumble soil', the walls are sloped to within 1.5 metres of the bottom of the excavation at an angle of not less than 45 degrees measured from the vertical, and - (c) if the soil is classified as 'soft, sandy or loose soil', the walls are sloped from the bottom of the excavation at an angle of not less than 45 degrees measured from the vertical. ## Loose materials 452 An employer must ensure that loose materials are scaled and trimmed from the sides of an excavation if workers may be on or near the sides. ## Spoil piles - 453 An employer must ensure that a spoil pile is piled so that - (a) the leading edge of the pile is at least 1 metre away from the edge of the excavation, - (b) the slope of a spoil pile adjacent to the excavation is at an angle of not more than 45 degrees from the horizontal, and - (c) loose materials are scaled and trimmed from the spoil pile. ## Power pole support 454 An employer must ensure that work that disturbs the ground in the vicinity of an overhead power line is performed in a manner that does not reduce the original support provided for power line poles. ## Safe entry and exit 455 (1) An employer must ensure that if a worker is required to enter a tren…