Trench Excavation and Shoring

Document Number: [SWP-NUMBER]

Revision Date: [DATE]

Next Review Date: [NEXT REVIEW DATE]

Department: [DEPARTMENT NAME]

1. Scope

This safe work procedure outlines the requirements for safe trench excavation and shoring practices to prevent cave-ins and other excavation-related injuries. It applies to all excavation and trenching activities where workers are required to enter the excavation. This procedure does not apply to excavations in solid rock where there is no risk of collapse, or where a professional engineer has attested that shoring is unnecessary.

2. Definitions

Excavation Any man-made cut, cavity, trench, or depression in an earth surface, formed by earth removal. [7]

Trench 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. [6]

Shoring (Shoring system) 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. [6]

Sloping (Sloping system) A method of protecting employees from cave-ins by excavating to form sides of an excavation that are inclined away form the excavation so as to prevent cave-ins. [6]

Shield (Shield system) A structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees within the structure. [6]

3. Responsibilities

3.1 Supervisors

• Supervisors must ensure that shoring materials are installed from the top down and removed in reverse order. [1]
• Supervisors must ensure that shoring or manufactured or prefabricated support systems are 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. [1]
• Supervisors must ensure that voids between the shoring and the excavation face are backfilled or blocked, unless otherwise indicated by the manufacturer or a professional engineer, in writing. [1]
• Supervisors must ensure that the walls of an excavation or trench are supported by adequate shoring and bracing or caging except under specific conditions. [3]
• Supervisors must ensure that workers are not allowed to enter an excavation or trench 1 219 mm 4 ft.) or more in depth, and workers shall not enter unless the requirements of section 12.2 are complied with. [3]
• Supervisors must ensure that excavated material is kept at least 609 mm (2 ft.) away from the edge of excavations or trenches. [2]
• Supervisors must ensure that every excavation and trench is kept reasonably free of water. [2]
• Supervisors must ensure that hazardous liquids or gases and explosives are not stored in excavations or trenches. [2]
• Supervisors must ensure that adequate ventilation precautions are taken to prevent the accumulation of hazardous gases in the excavation or trench. [2]
• Supervisors must ensure that a worker is working on surface where he can observe the workers working in the excavation or trench. [8]
• Supervisors must ensure that an excavation or trench is adequately illuminated, has adequate warning lights conspicuously displayed, and has a barricade at all times while workers are working in the excavation or trench. [8]
• Supervisors must ensure that the walls and crests of an excavation or trench, when cut in solid rock and are not stable, are supported by rock bolts, wire mesh or shoring or other equivalent method. [8]
• Supervisors must ensure that ladders are placed in trenches at intervals of 15 linear metres or fractions thereof and in such manner as to follow the progress of the works.
• Supervisors must post an experienced person at ground level so that he may detect faults, earth breaking away or any other source of danger.
• Supervisors must ensure that the banks of an excavation or trench are shored solidly with quality materials in accordance with the plans and specifications of an engineer.
• Supervisors must verify whether there is underground piping within the perimeter of the works to be carried out and, where applicable, situate its exact location on the ground.
• Supervisors must ensure that utility poles, posts or similar structures are supported or removed when they are within 3 048 mm (10 ft.) of an excavation or trench more than 1 219 mm 4 ft.) deep. [3]

3.2 Workers

• Workers must follow safe shoring procedures.
• Workers must not enter an excavation to remove shoring materials if ground conditions have deteriorated so as to make entry for shoring removal unsafe. [1]
• Workers shall not stand under any load or in the area where a load may land. [8]
• Workers must wear CSA approved safety headwear and footwear. [2]
• Workers shall not install or remove shoring from a position inside a trench. [2]

4. Potential Hazards and Risks

Hazard	Risk	Control Measures
Cave-in	Entrapment, crushing injuries, or death	Ensure proper sloping, shoring, or shielding is in place. A competent person must inspect the excavation daily.
Underground utility strike	Electrocution, explosion, or service disruption	Locate and identify all underground utilities before excavating. Use safe digging practices near utilities.
Falling objects	Head injuries, lacerations, or crushing injuries	Keep excavated materials at least 2 feet away from the edge of the excavation. Use barriers to prevent materials from falling into the excavation.
Hazardous atmosphere	Asphyxiation, poisoning, or explosion	Provide adequate ventilation. Test the atmosphere for hazardous gases before entry. Use respiratory protection if necessary.
Slips, trips, and falls	Sprains, fractures, or other injuries	Provide safe access and egress, such as ladders or ramps. Keep access routes clear of obstructions.
Mobile equipment	Struck-by injuries	Use high-visibility clothing. Establish traffic control measures. Use warning signs and barricades.
Water accumulation	Drowning, electrocution, or collapse of excavation	Ensure proper drainage. Use pumps to remove accumulated water.
Inadequate lighting	Slips, trips, and falls	Provide adequate lighting. Use fall protection measures when working at heights.

5. Personal Protective Equipment (PPE)

The following personal protective equipment (PPE) is required:

• Hard Hat: To protect workers from head injuries. [2]
• Safety Glasses: To protect workers' eyes from dust and debris.
• Safety Boots: To protect workers' feet from injuries. [2]
• Respirator: To provide respiratory protection in hazardous atmospheres.
• High-Visibility Clothing: To ensure workers are visible to equipment operators.

Inspect all PPE before each use for damage or defects. Replace damaged or defective PPE immediately.

6. Equipment and Tools

The following equipment and tools are required for safe trench excavation and shoring:

• Measuring Tape: Used to measure the depth of the excavation to ensure that the appropriate protective system is used.
• Atmospheric Testing Equipment: Used to test the atmosphere in the excavation for hazardous gases, vapors, or oxygen deficiency.
• Ladder or Ramp: Used to provide a safe means of access and egress to the excavation.
• Shoring System: Used to shore the sides of the excavation to prevent cave-ins.
• Trench Box or Shield: Used to shield workers from cave-ins.

Inspect ladders for damage or defects before each use. Ensure ladders extend at least 3 feet above the excavation.

7. Pre-Job Requirements

7.1 Training and Competency

Training and Competency: All workers involved in trench excavation and shoring must be trained and competent in the following areas: Hazard recognition, safe excavation practices, shoring techniques, confined space entry (if applicable), emergency procedures, and the proper use of PPE.

7.2 Pre-Job Briefing

Pre-Job Briefing: A pre-job briefing must be conducted before the start of each shift to discuss the hazards, control measures, and safe work procedures. All workers must attend the briefing and sign the attendance sheet.

7.3 Work Area Preparation

Work Area Preparation: Before beginning any excavation work, the following steps must be taken: Locate and mark all underground utilities. Ensure that all workers are aware of the hazards and control measures. Establish a communication system. Set up barricades and warning signs. Ensure that all equipment is in good working order.

8. Safe Work Procedure Steps

1. Locate Underground Utilities: Before starting any excavation work, identify the location of all underground utilities in the area. Notify the utility companies and follow their requirements for safe excavation practices. [4]
2. Inspect the Excavation: A competent person must inspect the excavation daily before the start of work and after any event that could affect the stability of the excavation. The inspection must include checking for signs of cave-ins, hazardous atmospheres, and other hazards.
3. Select a Protective System: Based on the soil type and depth of the excavation, determine the appropriate protective system to use. This may include sloping, shoring, or shielding.
4. Slope the Excavation: If sloping is used, ensure that the sides of the excavation are sloped at an angle that is safe for the soil type. Refer to the regulations for specific slope requirements. [4]
5. Install Shoring: If shoring is used, install the shoring system according to the manufacturer's instructions or a design by a professional engineer. Ensure that the shoring is in good condition and properly installed. [1]
6. Use Shielding: If shielding is used, ensure that the trench box or shield is of adequate size and strength for the depth of the excavation and the soil conditions. Follow the manufacturer's instructions for proper use.
7. Provide Safe Access: Provide a safe means of access and egress to the excavation, such as a ladder or ramp. Ensure that the access point is located within 25 feet of any worker in the excavation.
8. Control Excavated Materials: Keep excavated materials and equipment at least 2 feet away from the edge of the excavation to prevent them from falling into the excavation. [9]
9. Test for Hazardous Atmospheres: Test the atmosphere in the excavation for hazardous gases, vapors, or oxygen deficiency before entry. If a hazardous atmosphere is present, provide ventilation or respiratory protection.
10. Use Personal Protective Equipment (PPE): Ensure that all workers in the excavation wear appropriate PPE, including hard hats, safety glasses, and high-visibility clothing.
11. Surface Watch: A competent person must be stationed at the surface of the trench to warn workers in the trench of danger and to provide emergency help.
12. Backfill the Excavation: Backfill the excavation as soon as possible after the work is completed. Remove the protective system in a safe manner, working from the bottom up.

9. Precautions and Safety Measures

• A competent person must inspect the excavation daily before the start of work and after any event that could affect the stability of the excavation. - The competent person must be trained and experienced in excavation safety.
• Shoring materials must be lumber graded Number 2 or better from specific species groups. - Ensure lumber is properly graded and inspected before use. [1]
• 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. - Ensure shoring is installed to the correct height. [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. - Clearly mark the exclusion zone. [5]
• Safe means of entry and exit must be provided for an excavation a worker enters. 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. - Use ladders, ramps, or stairs. [5] [5]

10. Emergency Procedures

10.1 General Emergency Response

In any emergency situation, the primary concern is the safety of all personnel.

10.2 Specific Emergency Scenarios

• Cave-in occurs: Evacuate the trench immediately. Ensure all personnel are accounted for. Contact emergency services if necessary. Do not re-enter the trench until it has been inspected and deemed safe by a competent person.
• Worker injury: Evacuate the trench immediately. Provide first aid and contact emergency services. Investigate the cause of the injury and implement corrective actions.
• Underground utility strike: Evacuate the trench immediately. Contact the utility company and emergency services. Do not re-enter the trench until the utility has been shut off and the area is deemed safe.

11. Incident Reporting and Investigation

All incidents, including near misses, must be reported to the supervisor immediately. A formal incident report must be completed within 24 hours.

A thorough investigation will be conducted to determine the root cause of the incident and to implement corrective actions to prevent recurrence.

Approved by: [NAME AND POSITION]

Date: [APPROVAL DATE]

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