Trench Excavation

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# OCCUPATIONAL HEALTH AND SAFETY REGULATION (cont.) ## Sloping and shoring requirements (cont.) B.C. Reg. 296/97 WORKERS COMPENSATION ACT # OCCUPATIONAL HEALTH AND SAFETY REGULATION # Part 20 - Construction, Excavation and Demolition (3) If end shoring is required, the walers for the end shoring must be installed to bear against the walers that extend along the sides of the trench, or in a manner that will provide equivalent structural restraint. (4) End shoring must be designed by a professional engineer if the end shoring waler length exceeds 1.8 m (6 ft.). (5) Shoring must extend from at least 30 cm (1 ft.) above ground level to as close to the bottom of the trench as the material being installed will allow, but in no case more than 60 cm (2 ft.) from the bottom. (6) Shoring need not extend above ground level where traffic crossing plates need to be used, provided that other measures are taken to prevent excavated or other material from entering the excavation. [am. B.C. Regs. 253/2001, S. 15; 258/2008, App. F, S. 4.] ## Timber shoring and grades - 20.82 (1) Timber shoring materials must be lumber graded Number 2 or better from the following species groups: Douglas fir-larch, hemlock-fir, spruce-pine-fir or coast-Sitka-spruce. (2) All lumber must be graded to the National Lumber Grades Authority Standard Grading Rules for Canadian Lumber. [am. B.C. Reg. 312/2003, App. A, S. 24.] ## Safe shoring procedures - 20.83 (1) Shoring materials must be installed from the top down and removed in reverse order. (2) Workers must not enter an excavation to remove shoring materials if ground conditions have deteriorated SO as to make entry for shoring removal unsafe. (3) Shoring or manufactured or prefabricated support systems must be installed in firm contact with the faces of the excavation, and in a manner which ensures no loss of soil from behind or below the bottom of the shield or shoring while the excavation is open. (4) Unless otherwise indicate…

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This information is provided free of charge by the Department of Industrial Relations from its web site at www.dir.ca.gov. These regulations are for the convenience of the user and no representation or warranty is made that the information is current or accurate. See full disclaimer at https://www.dir.ca.gov/od_pub/disclaimer.html Subchapter 4. Construction Safety Orders Article 6. Excavations Return to index New query ## §1541.1. Requirements for Protective Systems. (a) Protection of employees in excavations. (1) Each employee in an excavation shall be protected from cave-ins by an adequate protective system designed in accordance with Section 1541.1(b) or (c) except when: (A) Excavations are made entirely in stable rock; or (B) Excavations are less than 5 feet in depth and examination of the ground by a competent person provides no indication of a potential cave-in. (2) 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. (b) Design of sloping and benching systems. The slopes and configurations of sloping and benching systems shall be selected and constructed by the employer or his designee and shall be in accordance with the requirements of Section 1541.1(b)(1), Section 1541.1(b)(2), Section 1541.1(b)(3), or Section 1541.1(b)(4), as follows: (1) Option (1) - Allowable configurations and slopes. (A) 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. (B) Slopes specified in Section 1541.1(b)(1)(A) shall be excavated to form configurations that are in accordance with the slopes shown for Type C soil in Appendix B to this article. (2) Option (2) - Determination of slopes and configurations using Appendices A and B. Maximum allowable slopes, and allowable configurations f…

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# Part 20 - Construction, Excavation and Demolition (cont.) ## Height limitations (cont.) WORKERS COMPENSATION ACT # OCCUPATIONAL HEALTH AND SAFETY REGULATION Part 20 Construction, Excavation and Demolition B.C. Reg. 296/97 ## Positioning equipment 20.94 Whenever possible, power machines excavating banks must be positioned so that the operator is on the side away from the bank and with the boom positioned closest to the side of the excavation. ## Water accumulation - 20.95 (1) Water must not be allowed to accumulate in an excavation if it might affect the stability of the excavation or might endanger workers. (2) Erosion of slopes by surface water must be prevented if workers may be endangered. Table 20-1: Trench support structures Size and spacing of members¹ (metric figures) <table><tr><th colspan="3">Uprights</th><th colspan="2">Walers</th><th colspan="4">Cross Braces</th></tr><tr><td></td><td></td><td></td><td></td><td rowspan="2">Maximum vertical spacing (metres)</td><td colspan="2">Width of trench (metres)</td><td rowspan="2" colspan="2">Maximum spacing (metres) Vertical Horizontal</td></tr><tr><td>Trench depth (metres)</td><td>Minimum dimensions (millimetres)2</td><td>Maximum spacing (metres)</td><td>Minimum dimensions (millimetres)²</td><td>Up to 1.8 Minimum</td><td>1.8-3.7 dimensions (millimetres)2</td></tr><tr><td colspan="3">Type A: Hard and solid soil</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>1.2-3³</td><td>38 X 235</td><td>1.8</td><td>89 X 140</td><td>1.2</td><td>89 X 89</td><td>140 X 140</td><td>1.2</td><td>1.8</td></tr><tr><td>3-4.6</td><td>38 X 235</td><td>1.2</td><td>140 X 140</td><td>1.2</td><td>89 X 140</td><td>140 X 191</td><td>1.2</td><td>1.8</td></tr><tr><td>4.6-6</td><td>38 X 235</td><td>Close tight</td><td>140 X 140</td><td>1.2</td><td>140 X 191</td><td>191 X 191</td><td>1.2</td><td>1.8</td></tr><tr><td colspan="3">Type B: Soil likely to crack or crumble</td><td></td><td></td><td></td><td></td><td></…

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# Occupational Safety and Health Administration (cont.) ## Definitions applicable to this subpart. (cont.) Shield (Shield system) means a structure that is able to withstand the forces imposed on it by a cave-in 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 as "trench boxes" or "trench shields." Shoring (Shoring system) means a structure such as a metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and which is designed to prevent cave- ins. Sides. See "Faces." Sloping (Sloping system) means a method of protecting employees from cave-ins by excavating to form sides of an excavation that are inclined away from the excavation so as to prevent cave- ins. The angle of incline required to prevent a cave-in varies with differences in such factors as the soil type, environmental conditions of exposure, and application of surcharge loads. Stable rock means natural solid mineral material that can be excavated with vertical sides and will remain intact while exposed. Unstable rock is considered to be stable when the rock material on the side or sides of the excavation is secured against caving-in or movement by rock bolts or by another protective system that has been designed by a registered professional engineer. Structural ramp means a ramp built of steel or wood, usually used for vehicle access. Ramps made of soil or rock are not considered structural ramps. 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 …

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# Trenching and Excavation (cont.) ## What should occur before beginning an excavation? (cont.) - Check areas near the site for potential hazards and sources that can impact the stability of the soil. Be aware that nearby vehicles and equipment can cause the soil to vibrate and then collapse. - Determine if nearby buildings or structures and their foundations may put pressure on the soil and affect the walls of the trench. - Test for hazardous gas, vapours, and dust before entering. Test for oxygen levels in the space before entering, and during the work as required. - Plan appropriate organization of the work site, and good housekeeping practices including moving debris and excavated soil far enough away from the excavation site. - Remove water from the excavation. - Protect workers from falling into the excavation. - Identify appropriate personal protective equipment including high visibility apparel for vehicular traffic and make sure every worker wears them as required. - Have a worker above ground when a worker is working in the trench to warn those in the trench of danger and to provide emergency help. - Determine if the trench is considered a confined space If so, do not allow workers to enter the trench until the requirements of the organization's confined space program are met, including entry permits and training. - Prepare work permits for work in confined spaces, as appropriate. - Have a means of exit provided from the inside of the trench, usually no more than 8m (25 ft) away from any worker in the trench. - Plan for adverse weather conditions (e.g. hot or cold environments, storms, etc.). - Prepare an emergency plan and rescue procedures. - Keep first aid equipment at the site. - Educate and train workers about all existing and potential hazards and risks and appropriate safety measures. ## What factors determine what is the appropriate protective system to use? In general, trenches that are 1.2 metres (4 feet) deep or great…

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# OCCUPATIONAL HEALTH AND SAFETY REGULATION (cont.) ## Trench support structures (cont.) B.C. Reg. 296/97 WORKERS COMPENSATION ACT # OCCUPATIONAL HEALTH AND SAFETY REGULATION # Part 20 - Construction, Excavation and Demolition ## Spoil piles 20.86 If the average depth of a spoil pile which is adjacent to a supported excavation exceeds 60 cm (2 ft), the selection of the shoring or shielding must take into account the resulting increase in lateral soil pressure. ## Entry and exit - 20.87 (1) Safe means of entry and exit must be provided for an excavation a worker enters. (2) If workers are required to enter a trench over 1.2 m (4 ft) deep, the safe point of entry and exit must be located within 8 m (25 ft) of the workers and the excavation must be safely supported or sloped to the entry and exit location. (3) Walkways must be secured to prevent dislodgment. (4) The open side of an access route into an excavation used by mobile equipment must have a curb. ## Guarding 20.88 If an excavation is a hazard to workers, it must be effectively covered or guarded. ## Excavation crossings 20.89 A walkway across an excavation must be at least 50 cm (20 in) wide, and if crossing an excavation over 1.2 m (4 ft) deep, be equipped with guardrails, meeting the require- ments of Part 4 (General Conditions), on both sides. ## Excavated materials - 20.90 (1) Excavated material must be kept back a minimum distance of 60 cm (2 ft) from the edge of a trench excavation and 1.2 m (4 ft) from any other excavation. (2) Under no circumstances may excavated material be piled SO that it endangers workers. ## Use of skips or buckets 20.91 If a skip or bucket is used to remove material from an excavation, horizontal shoring members must be shielded from dislodgment with vertical planking. ## Scaling and trimming 20.92 The sides of an excavation must be scaled and trimmed or otherwise stabilized to prevent slides of material or falls of rock which could endanger workers. #…

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## §1541.1. Requirements for Protective Systems. (cont.) use, then such material or equipment shall be removed from service, and shall be evaluated and approved by a registered professional engineer before being returned to service. (e) Installation and removal of supports. (1) General. (A) Members of support systems shall be securely connected together to prevent sliding, falling, kickouts, or other predictable failure. (B) Support systems shall be installed and removed in a manner that protects employees from cave-ins, structural collapses, or from being struck by members of the support system. (C) Individual members of support systems shall not be subjected to loads exceeding those which those members were designed to withstand. (D) Before temporary removal of individual members begins, additional precautions shall be taken to ensure the safety of employees, such as installing other structural members to carry the loads imposed on the support system. (E) 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. (F) Backfilling shall progress together with the removal of support systems from excavations. (2) Additional requirements for support systems for trench excavations. (A) Excavation of material to a level no greater than 2 feet below the bottom of the members of a support system shall be permitted, but only if the system is designed to resist the forces calculated for the full depth of the trench, and there are no indications while the trench is open of a possible loss of soil from behind or below the bottom of the support system. (B) Installation of a support system shall be closely coordinated with the excavation of trenches. (f) Sloping and benching systems. Employees shall not be permitted to work on the faces of sloped or benched excava…

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146 (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 by shoring components; (b) shoring compon…

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# Trenching and Excavation (cont.) ## What factors determine what is the appropriate protective system to use? (cont.) - Water content of soil - Changes due to weather or climate - Surcharge loads (e.g., spoil, other materials to be used in the trench) and - Other operations in the area Always check the legislative requirements in your jurisdiction related to the use of protective systems. ## What are the different types of protective systems used to protect against cave-ins? There are two basic methods of protecting workers against cave-ins: - Sloping - Temporary protective structures (e.g., shoring, trench boxes, pre-fabricated systems, hydraulic systems, engineering systems, etc.) ## Sloping Sloping involves cutting back the trench wall at an angle that is inclined away from the work area of the excavation. The angle of slope required depends on the soil conditions. Benching is a similar method to sloping. ## Temporary protective structure WorkSafe Saskatchewan defines a temporary protective structure as "a structure or device in an excavation, trench, tunnel or excavated shaft that is designed to provide protection from cave-ins, collapse, sliding or rolling materials, and includes shoring, trench boxes, trench shields and similar structures." Shoring is a system that supports the sides or walls. Shoring requires installing aluminum, steel, or wood panels that are supported by screws or hydraulic jacks. Some systems can be installed without the workers entering the trench. This option provides additional safety for those workers. Wherever possible, install the shoring equipment as the excavation proceeds. If there is any delay between digging and shoring, no one should enter the unprotected trench. Trenching and Excavation CCOHS