excavation shoring

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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

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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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# Part 20 - Construction, Excavation and Demolition (cont.) ## Safe shoring procedures (cont.) WORKERS COMPENSATION ACT B.C. Reg. 296/97 # OCCUPATIONAL HEALTH AND SAFETY REGULATION Part 20 - Construction, Excavation and Demolition ## Trench support structures - 20.85 (1) Trench support structures, other than those designed by a professional engineer, must comply with Table 20-1 for the following relevant soil conditions: <table><tr><th>Soil type</th><th>Description of soil</th></tr><tr><td>A</td><td>hard and solid</td></tr><tr><td>B</td><td>likely to crack or crumble</td></tr><tr><td>C</td><td>soft, sandy, filled or loose</td></tr></table> (2) If Table 20-1 is to be used for a combination of supporting and sloping, the selection of shoring elements must be based on the overall depth of the excavation and the arrangement must conform to Figure 20-3. (3) Cross braces and trench jacks must be installed in a horizontal position and must be secured against dislodgment. (4) The minimum number of cross braces at each cross bracing location is determined by the trench depth as follows: <table><tr><th>Depth at location</th><th>Number of braces</th></tr><tr><td>up to 2.4 m (8 ft)</td><td>2</td></tr><tr><td>2.4 m to 3.7 m (8 ft to 12 ft)</td><td>3</td></tr><tr><td>3.7 m to 4.6 m (12 ft to 15 ft)</td><td>4</td></tr><tr><td>4.6 m to 6 m (15 ft to 20 ft)</td><td>5</td></tr></table> (5) At each cross bracing location the cross braces must be less than 1.2 m (4 ft) apart, and the uppermost cross brace must be within 60 cm (2 ft) of ground level. (6) Repealed. [B.C. Reg. 312/2003, App. B, S. 43.] (7) Hydraulic or pneumatic trench jacks must have a means of ensuring that they will not collapse in the event of loss of internal pressure. (8) Uprights must not spread outwards more than 15 degrees from the vertical when viewed along the trench. (9) Plywood may be substituted for two inch thick shoring elements provided that (a) the plywood is not less than 19 mm (3/4 i…

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# Part 20 - Construction, Excavation and Demolition (cont.) ## Work standards (cont.) WORKERS COMPENSATION ACT B.C. Reg. 296/97 # OCCUPATIONAL HEALTH AND SAFETY REGULATION Part 20 - Construction, Excavation and Demolition ## Underground utility services - 20.79 (1) Before excavating or drilling with powered tools and equipment, the location of all underground utility services in the area must be accurately determined, and any danger to workers from those utility services must be controlled. (2) Excavation or drilling work in proximity to an underground utility service must be undertaken in conformity with the requirements of the owner of that utility service. (3) Pointed tools must not be used to probe for underground petroleum and electrical utility services. (4) Powered equipment used for excavating must be operated so as to avoid damage to underground utility services or danger to workers. [am. B.C. Regs. 312/2003, App. E, S. 15; 312/2010, App. D, S. 3.] ## Removing nearby hazards 20.80 Trees, utility poles, rocks and similar objects adjacent to an area to be excavated must be removed or secured if they could endanger workers. ## Sloping and shoring requirements - 20.81 (1) Subject to section 20.78, before a worker enters any excavation over 1.2 m (4 ft.) in depth or, while in the excavation, approaches closer to the side or bank than a distance equal to the depth of the excavation, the employer must ensure that the sides of the excavation are (a) sloped as specified in writing by a qualified registered professional, (b) sloped at angles, dependent on soil conditions, which will ensure stable faces, but in no case may the slope or combination of vertical cut and slope exceed that shown in Figure 20-1, (c) benched as shown in Figure 20-2, (d) supported as specified in writing by a professional engineer, (e) supported in accordance with the minimum requirements of section 20.85, or (f) supported by manufactured or prefabricated t…

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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…