Excavations and Trenches

Transcription

1 Purpose Excavation and trenching are among the most hazardous work activities undertaken by the TNRD. This document outlines general requirements and specific safe work procedures to ensure the health and safety of employees who work in or around excavations as part of their job duties. These safe work practices are also designed to protect the general public who work or travel in the vicinity of excavations. Objective Before a worker enters any excavation over 1.2m (4ft) in depth shoring must be in place. Before a worker approaches closer to the side or bank, the excavation must be sloped, benched, shored or supported in accordance with Part 20 of the WCB Occupational Health & Safety Regulation or with the specifications and requirements of a registered professional engineer. Supervision Crew shall be familiar with the actual and potential hazards associated with work. Manager must ensure that workers under their direction and control are aware of the dangers associated with the work and perform their work in a safe manner. Qualified person on site shall ensure all the requirements of this procedure, related regulation, and applicable industry best practices are applied at all times. Hazards Hazards that workers may be exposed to when excavating around underground utilities include: Electrocution Explosive, flammable, combustible gases or fluids Toxic gases & vapours Drowning Cave-ins Contaminated soils Moving heavy equipment/machinery around excavations Vehicular traffic Silica/Asbestos May, 2017 Page 1

2 Worker Responsibility Each employee is responsible to carry out their work in accordance with the established safe excavation practices outlined in this document. Employees must also use and or wear protective equipment, devices and clothing as required for the hazards of the work. It is every employee s responsibility to ask questions about anything they do not understand or safe work procedures that are not clear. If any worker believes that there is a risk of injury to themselves, a co-worker or damage to a utility or piece of equipment, it is their duty to stop work immediately and correct the situation including contacting their supervisor to determine the next course of action. Safe Work Procedures: 1. Before excavating or drilling with powered tools and equipment the location of all underground utilities in the area must be accurately determined; mark location on asphalt to identify location of underground utilities and any danger to worker from the utility. Before you dig, call BC ONE. They will advise you of the following: 2. Which members have underground facilities in the proposed excavation area Transmit the information about the proposed activity to the member companies Inform you about your liability and provide you with a ticket number to confirm your request. Advise you to contact any other parties who may have underground facilities in the excavation area, as all facility owners are not members of BC ONE CALL. You must contact these non-members directly. Each member company will then contact you with information about where their facilities are buried in the proposed excavation area. Always wait for a response from all facility owners in the proposed excavation site before digging. Given the utility a minimum of three full working days notice for planned work. May, 2017 Page 2

3 3. NEVER cut into abandoned gas lines, damaged conduit, shake damaged utilities or open BC hydro high voltage vaults. Do not remove, contact, alter, pull, cut, repair, etc. any utility including conduit, unless directed and approved by the utility company owner. This approval must be in WRITING. 4. Mechanical digging is not permitted within the no mechanical dig zone boundary limit (1 m (3ft. 3in.) in any direction from the utility or its marked location) until it is exposed by hand digging or hydro-excavating at a sufficient number of locations to determine its exact positions and depths. Once the utility or service is adequately exposed, mechanical diggings is permitted up to 0.3m (12in.) of the utility. All Utility Locations must be painted or marked to indicate the safe hand dig area within the non-mechanized equipment zone. 5. Pointed tools must not be used for probing to locate underground gas lines or electrical utilities. 6. Traffic around the site must be controlled, and barricades, signs, and/or flag persons used as needed to control both vehicular and pedestrian traffic. 7. The Equipment Operator must operate the equipment safely and maintain full control. 8. Only an authorized person may be on mobile equipment while the equipment is in motion. 9. Excavated material must be kept back a minimum distance of 0.6 m (2 feet) from the edge of a trench excavation and 1.22 m (4 feet) from any other excavation. Excavated material must not be piled so it endangers workers. 10. The sides of an excavation must be scaled and trimmed or otherwise stabilized to prevent slides of material of falls of rock which could endanger workers. 11. Trees, utility poles, rocks or similar objects adjacent to an area to be excavated must be removed or secured if they could endanger workers. May, 2017 Page 3

4 12. Safe access must be provided in the immediate area where workers are employed in trenches over 1.22 m (4 feet deep). Ladders must extend from the bottom of the excavation at least 0.9 m (3 feet) above ground. 13. If an excavation is a hazard to workers, it must be effectively covered or guarded. 14. A worker must be designated as a spotter at all times when mechanical digging is undertaken. The spotter must maintain visual contact with the equipment operator and excavation at all times watching for underground utilities. The spotter must signal the equipment operator to stop digging immediately if any unexpected utilities are encountered. 15. All workers must maintain a safe distance from the radius of the backhoe bucket. Workers must never walk under a loaded bucket due to the danger of falling debris, hydraulic failure or operator error. Eye contact is required to be made with the operator prior to entering the hazard bite zone (radius of backhoe/excavator swing radius). 16. All equipment and machinery must maintain a safe distance from overhead hazards. The Limits of Approach as outlined in WorkSafeBC Regulation Table 19-1A must be adhered to when working in close proximity to powerlines. Table 19-1: General limits of approach Column 1 Voltage Column 2 Minimum approach distance for working close to exposed electrical equipment or conductors Phase to phase Metres Feet Over 750 V to 75 kv 3 10 Over 75 kv to 250 kv Over 250 kv to 550 kv 6 20 If the minimum distance in Table 19-1 cannot be maintained because of the circumstances of work or the inadvertent movement of persons or equipment, an assurance in writing must be signed by a representative of the owner of the power system. The assurance in writing form is referred to as a WCB form 30M Water must not be allowed to accumulate in an excavation if it might affect the stability of the excavation or endanger workers. Surface water must also be prevented from eroding the slopes of the excavation. May, 2017 Page 4

5 18. If unexpected contact is made with a utility, the accidental contact procedures must be followed as specified in this document. 19. If the excavation work is not complete at the end of the day, the excavation must be covered, fenced or otherwise made safe for the public. 20. Workers are not allowed to cut into abandoned gas lines or damaged conduit. Workers must not open BC Hydro High Voltage Vaults. Permission and direction must be obtained from the utility owner with regards to handling damaged or abandoned conduit. Document the name and contact information of the utility representative that provides the TNRD with guidance and direction. 21. When cutting Asbestos containing pipe, Asphalt or Concrete workers must suppress the dust by using wetting techniques and wear appropriate personal protective equipment. Ie. Respirator, Tyvek suit (disposable coverall), etc. 22. A Notice of Project must be filed 24hrs prior to a planned excavation / construction project if (a) the total cost of labour and materials for the work exceeds $100, 000 or the construction project includes a trench more than 1.2 m (4 feet) in depth and over 30 m (100 feet) in length or includes another type of excavation more than 1.2 m (4 feet) in depth, which a worker may be required to enter. May, 2017 Page 5

6 Sloping and Shoring Requirements 1. Before a worker enters any excavation over 1.2 m (feet) in depth or, while the excavation approaches closer to the side or bank than a distance equal to the depth of the excavation, the excavation slides must be sloped or supported as specified by a professional engineer or geoscientist, or shoring must be in place. In the event shoring cannot be used the sides of the excavation must be: a. Sloped to a safe angle no slop can be steeper than 0.9 m ( feet) horizontal to 1.22 m ( 4 feet) vertical (see Appendix), b. Benched bench width shall not be less than 1.5 times the height of its rise below (See Appendix B), c. Supported in accordance with the minimum requirements of section of the Regulation If the end of a trench over 4 feet in depth is not adequately sloped, end shoring must be installed unless: a. A worker in the trench is not required to approach closer to the end of the trench than a distance equal to the depth of the trench at that end, b. Where, for the prevailing soil conditions at the end of the trench, the permissible spacing of uprights equals or exceeds the width of the trench, or c. Otherwise authorized in writing by a professional engineer. 2. A safety spotter must be designated to each excavation while a worker is in the excavation to identify any potential hazard that may occur while the work is being performed. Equipment Operators and Truck Drivers may be designated as spotters, they must remain in a position while designated as the spotter to observe and communicate at all times with the excavation worker. 3. Any engineered excavation support system must have certified design documentation available on site. It must also be inspected daily and maintained in a fully effective condition. May, 2017 Page 6

7 Hazardous Atmospheres Atmospheric testing must be conducted in excavations over 1.22 m (4 feet) deep where hazardous atmospheres could reasonably be expected to exist. Instruction of Professional Engineer or Geoscientist Excavation work must be in accordance with the written instructions of a professional engineer if: a. The excavation is more than 6 m (20 feet) deep, b. Support structures other than as specified in Section of the WCB OSHR are used in the excavation, c. An improvement or structure (building) is adjacent to the excavation, d. The excavation is subject to vibration or hydrostatic pressure likely to result in ground movement hazardous to workers, or e. The ground slopes away from the edge of the excavation at an angle steeper than 0.9 m (3 feet) horizontal to 0.3 m ( 1 foot) vertical. Abandoned Utilities If you unexpectedly come across an underground utility that was not previously located, Stop digging, review BC One Call maps and location maps to determine if the utility locate was accidently missed. Call Manager for instructions. Workers are NOT allowed to cut conduit until the Utility owner advises that it is safe to do so and that they authorize the TNRD to perform the task. Violation of this requirement will result in a severe discipline up to termination of employment. Document ID Document Title RA Excavation and Trenching Risk Assessment SWP Working Safely with Mobile Equipment F Excavation and Trenching Safety Checklist WorkSafeBC Part 19 General limits of approach WorkSafeBC Part 20 Construction, Excavation and Demolition May, 2017 Page 7