gas piping in trenches

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# Trenching and Excavation (cont.) ## What are the hazards associated with trenching and excavation? (cont.) - Contact with buried service lines such as electrical, natural gas, water, sewage, telecommunications, etc. - Contact with overhead electrical lines. - Slips, trips and falls as workers climb on and off equipment, or from inappropriate access and egress methods. - Being struck by moving machinery, or by falling or flying objects. - Hazards related to materials handling (e.g., lifting, struck by, crushed between, etc.). ## What is meant by soil types? Definitions of soil types vary by jurisdiction in Canada. In addition, some jurisdictions have not defined soil types, but do require preventative measures when an excavation reaches a certain depth or proportion. When a soil type is defined, the purpose is to try to identify or predict the potential for the soil to move and cause a collapse while the work is being done. Soil types typically use a scale of 1 to 4 where 1 is hard and dense to 4 which is loose, soft, wet or muddy soil, or a scale of A to C where A is hard and solid, and C is soft, sandy, filled or loose. The soil type is determined by the characteristics of the soil's consistency, ease of removal, appearance, ability to excavate with hand tools vs. machine, water seepage, whether the soil has been excavated before, etc. ## What should occur before beginning an excavation? The employer or supervisor is responsible for the work, and must take the necessary steps to identify all the hazards and risks before beginning any work. These steps include to: - Identify the soil type(s) related to the excavation or trench you are going to dig. Soil properties often vary widely within a single trench (e.g., the soil type changes from top to bottom and along the length of a trench). - Look for the legislative requirements that apply in your jurisdiction and the type of protective measures to be taken. - Locate all buried services. Contact t…

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# EXCAVATION CHECKLIST (To be completed by a Competent Person) (cont.) ## Indicate for each item: YES - NO - or N/A for not applicable (cont.) <table><tr><th>D. Structural ramps used for equipment designed by a registered professional engineer (RPE).</th><th></th></tr><tr><td>E. Ramps constructed of materials of uniform thickness, cleated together on the bottom, equipped with no-slip surface.</td><td></td></tr><tr><td>F. Employees protected from cave-ins when entering or exiting the excavation.</td><td></td></tr><tr><td>4. Wet Conditions:</td><td></td></tr><tr><td>A. Precautions take to protect employees from the accumulation of water.</td><td></td></tr><tr><td>B. Water removal equipment monitored by a competent person.</td><td></td></tr><tr><td>C. Surface water or runoff diverted or controlled to prevent accumulation in the excavation.</td><td></td></tr><tr><td>D. Inspections made after every rainstorm or other hazard-increasing occurrence.</td><td></td></tr><tr><td>5. Hazardous Atmosphere:</td><td></td></tr><tr><td>A. Atmosphere within the excavation tested where there is a reasonable possibility of an oxygen deficiency, combustible or other harmful contaminant exposing employees to a hazard. B. Adequate precautions taken to protect employees from exposure to an atmosphere containing less than 19.5% oxygen and/or to other hazardous atmospheres.</td><td></td></tr><tr><td>C. Ventilation provided to prevent employee exposure to an atmosphere containing flammable gas in excess of 10% of the lower explosive limit of the gas.</td><td></td></tr><tr><td>D. Testing conducted often to ensure that the atmosphere remains safe. E. Emergency equipment, such as breathing apparatus, safety harness and lifeline, and/or basket stretcher readily available where hazardous atmospheres could or do exist.</td><td></td></tr><tr><td>F. Employees trained to use personal protective and other rescue equipment.</td><td></td></tr><tr><td>G. Safety harness and lifeline used and individually a…

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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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SAMPLE-Excavation Checklist # EXCAVATION CHECKLIST (To be completed by a Competent Person) SITE LOCATION: <empty> DATE: <empty> TIME: <empty> COMPETENT PERSON: <empty> SOIL TYPE (See attached form): <empty> SOIL CLASSIFICATION: <empty> EXCAVATION DEPTH: <empty> EXCAVATION WIDTH: <empty> TYPE OF PROTECTIVE SYSTEM USED: <empty> ## Indicate for each item: YES - NO - or N/A for not applicable <table><tr><th>1. General Inspection of Jobsite:</th><th></th></tr><tr><td>A. Excavations, adjacent areas, and protective systems inspected by a competent person daily before the start of work.</td><td></td></tr><tr><td>B. Competent person has the authority to remove employees from the excavation immediately.</td><td></td></tr><tr><td>C. Surface encumbrances removed or supported.</td><td></td></tr><tr><td>D. Employees protected from loose rock or soil that could pose a hazard by falling or rolling into the excavation.</td><td></td></tr><tr><td>E. Hard hats worn by all employees.</td><td></td></tr><tr><td>F. Spoils, materials, and equipment set back at least two feet from the edge of the excavation.</td><td></td></tr><tr><td>G. Barriers provided at all remotely located excavations, wells, pits, shafts, etc.</td><td></td></tr><tr><td>H. Walkways and bridges over excavations four feet or more in depth are equipped with standard guardrails and toeboards.</td><td></td></tr><tr><td>I. Warning vests or other highly visible clothing provided and worn by all employees exposed to public vehicular traffic.</td><td></td></tr><tr><td>J. Employees required to stand away from vehicles being loaded or unloaded.</td><td></td></tr><tr><td>K. Warning system established and utilized when mobile equipment is operating near the edge of the excavation.</td><td></td></tr><tr><td>L. Employees prohibited from going under suspended loads.</td><td></td></tr><tr><td>M. Employees prohibited from working on the faces of slopes or benched excavations above other employees.</td><td></td></tr><tr><td>2. Uti…

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# Why Are Trenches Dangerous? A trench is an excavation deeper than it is wide. (cont.) ## Before digging (cont.) BEGIN Excavation INSTRUCTION ZONE ROADWAY SAFETY 2 # How Do We Prevent Cave-Ins? Trenches 5 feet or deeper require support.* ## Sloping • Soil angled to increase stability ## Benching • Steps in trench wall Shoring Support system made of posts, wales, struts, and sheeting or hydraulic shoring ## Shielding Protective frame or box, to protect workers after a cave-in Keep spoil piles away from trench edge + *Unless in stable rock (see definition).

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# Trenching and Excavation (cont.) ## Temporary protective structure (cont.) - Trench Boxes are commonly used in open areas that are away from utilities, roadways, and foundations. Trench boxes can be used to protect workers in cases of cave-ins, but not to shore up or support trench walls. They can support trench walls if the space between the box and the trench wall is backfilled with soil and compacted properly. Otherwise, a cave-in or collapse may cause the trench box to tilt or turn over. Workers should not be present in the box when it has to be moved. - Other: In some cases, the trench or excavation walls are made of rock but are not entirely stable. Support the walls by using rock bolts, wire mesh, or a method that provides equivalent support. ## What should NOT be done during an excavation? - Do not enter an unprotected trench deeper than 1.2 metres (4 feet), or as specified in the legislation. - Do not start digging before locating and de-energizing the buried services. - Do not enter a trench before testing the air for hazardous gasses and vapours, or the lack of oxygen. - Do not place the sections of pipes, piles of spoil, unused tools, and timber, and other materials within 1 metre from the trench's edge. - Do not rely on natural freezing to act as a method of soil stabilization. - Do not work under suspended or raised loads and materials. - Do not stand behind a backing vehicle. ## What can be included in a trenching and excavation inspection checklist? The following are some points to consider. Each circumstance will be different, so be sure to adapt the questions to suit your situation. ## Underground or Utility Services - Know the contact numbers? - Located, identified and informed respective parties? - Grounded, isolated, de-energized, or protected from unplanned release? ## Housekeeping Trenching and Excavation CCOHS

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CCOHS CCHST Canadian Centre for Occupational Health and Safety Centre canadien d'hygiène et de sécurité au travail Health and Safety Programs # Trenching and Excavation ## On this page What is meant by a trench and an excavation? What are the hazards associated with trenching and excavation? What is meant by soil types? What should occur before beginning an excavation? What factors determine what is the appropriate protective system to use? What are the different types of protective systems used to protect against cave-ins? What should NOT be done during an excavation? What can be included in a trenching and excavation inspection checklist? ## What is meant by a trench and an excavation? Generally speaking, an excavation is a hole in the ground as the result of removing material. A trench is an excavation in which the depth exceeds (is bigger than) the width. ## What are the hazards associated with trenching and excavation? Working in trenches and excavations is hazardous to both the workers who work inside them, and to workers on the surface. The hazards include: - Cave-ins or collapses that can trap or crush workers. - Equipment or excavated soil falling on workers (e.g., equipment is operated or soil and debris is stored too close to the excavation). - Falling into the trench or excavation. - Flooding or water accumulation. - Exposure to a hazardous atmosphere (e.g., gas, vapour, dust, biological contaminants, or lack of oxygen). Trenching and Excavation CCOHS

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# A Road Construction Industry Consortium Awareness Program # Trenching ## Why Are Trenches Dangerous? A trench is an excavation deeper than it is wide. Trenches can kill: • Workers can be buried alive. • Cave-ins can result from stresses in walls, nearby moving vehicles and equipment, or spoil piles. • Water can collect in the bottom. • Flammable and toxic gases can build up. • Gas from nearby sewer or gas lines can seep into the trench. Before digging: • Call electrical, gas, and communications utilities. • Use extreme caution with equipment. Trenches more than 4' deep meet OSHA's definition of a confined space. 26 26 26 # Roadway Safety Post warning signs at ground level. Make anyone who must enter the area aware of the overhead lines. Here are two tips for operators: • Mark a safe route for repeated travel. . Slow down. ## What If Contact Happens? Do not touch equipment or a person in contact with electricity. Get the line de-energized. If you are in a vehicle that contacts electricity, stay in the vehicle and do not contact any metal. If you must exit, jump clear and slowly shuffle away. Keep your feet together to help prevent current from running through your body. ## Can We Be Safe Around Buried Utilities? Before digging, call the electrical, gas, and communica- tions utilities. Review marked out areas. The mark out may not be exact, so dig by hand within 3 feet of it. When digging, look for: • foreign debris in excavation, . changes in mixed-up soil types, . asphalt patches or depres- sions indicating previous digging, and • concrete, plastic, or gravel. 4995 3

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# Exposure To Vehicular Traffic [29 CFR 1926.651(d)] (cont.) ## Emergency Rescue Equipment (cont.) This material is for training use only # Hazardous Atmospheres [29 CFR 1926.651(g)] ## Trenches are confined spaces! Check for: ✓ Oxygen deficiency, ↓ Explosives/Flammables, - Toxins; and to ensure acceptable atmospheric conditions through: - Atmospheric testing, - Removal of the substance, ↓ Proper ventilation, ✓ Respiratory protection, - etc. BW GASALERTMAX LOW ALARM 000 000 CO pp 196 000 02 % 'D 1 CAL MAX TWA Lab Safety Supply ## Testing and Controls Atmospheric testing is required where oxygen deficiency (less than 19.5 percent oxygen), or a hazardous atmosphere (flammable and/or toxic) exists or could reasonably be expected to exist. The competent person must be able to recognize where these conditions are expected. Some gases are heavier than air and can accumulate at the bottom of the trench. For example, hydrogen sulfide, carbon dioxide, and vapors from fuels are heavier than air. Other gases, like methane and carbon monoxide, are lighter than air and this is important to know when sampling. There may also be oxygen deficient situations where purging with an inert gas had occurred (e.g. decommissioned gas lines). Remember sources may come from outside the trench and "creep”in or come from - inside the trench (i.e. gas lines, contaminated soil, gas-powered tools/equipment, etc.). OR-OSHA 302 Excavation Safety 12

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# Near-Misses and Cave-Ins Described by Interview Participants (cont.) ## Jobsite Visits (cont.) depth from 5 to 16 feet, and protective systems in use were aluminum hydraulic shoring, slide rail systems, and sloping. On each site, the interviewed laborers and operators (a total of 5) were able to identify the competent person. The workers appeared knowledgeable about trench safety issues, such as the requirements for protective systems, soil testing, and means of egress. All employees wore hard hats, safety glasses, work boots, and safety vests. All of the jobs appeared to be well-planned before the start of excavation work, as indicated by the fact that appropriate safety equipment (personal protective equipment, measurement devices, and trench protection equipment) was onsite for use as necessary. ## Review of Media Coverage of Trenching Incidents The authors reviewed newspaper and television coverage of 18 excavation-related deaths that occurred throughout the United States during the project period (November 2003 through January 2005). Most reports were identified through the internet blog Confined Space, (http://spewingforth.blogspot.com). In most cases, the deaths resulted from suffocation or serious injury caused by trench collapses. The authors reviewed the coverage to assess its potential for raising public awareness about how these deaths may be prevented. In some cases the article clearly stated that the trench was five feet deep or greater and was unprotected, in violation of the OSHA standard. Sometimes a trench safety expert, such as an OSHA staff member, provided information on the proper use of trench protective systems, including in one case a drawing of a trench shield. Also, factors that increase the risk of cave-ins were discussed, such as waterlogged soil following a rainstorm. ## Discussion and Conclusions There is broad consensus among the experts cited in this report that consistently implementing the requirements of the OSHA excavatio…

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# Trenching and Excavation (cont.) ## Housekeeping (cont.) - Excavated material, pipes etc. are placed 1 metre away from the edge of the excavation or trench wall? - Are pumps available to remove water? - Is the base and foot of the ladder secure, and free of garbage or water? - Are materials placed on the site obstructing the worker's or vehicle's ability to move freely? - Are established traffic controls used, where required, including adequate signage, personnel, and lighting? - Has the excavation been marked to make the workers and others aware of the excavation (e.g., fence, flags, or other safeguards)? - Are sanitary facilities available at the site, as appropriate? ## General - Are proper barriers or guardrails in place to protect anyone or equipment falling into the excavation or trench? - Has the air in the excavation been tested for low oxygen, and hazardous gasses and vapours? - Is a safe means of entry and exit provided such as a sufficiently long and secured ladder placed at appropriate distances (within 25 feet of all workers)? - Are cracks visible in the ground around the trench or excavation that may indicate soil movement? - Are there any signs of water seeping into the trench or excavation? - Are workers wearing appropriate PPE (e.g., hard hats, respirators, , safety boots, hearing protection)? - Are high visibility vests or clothing provided and worn by all exposed to vehicular traffic? - Is first aid equipment available at the site? - Are operators qualified to operate the heavy machinery or equipment? - Does a competent person regularly inspect the excavation (at the start of each shift before work begins or after any event likely to have affected the strength or stability of the excavation)? - Is there a competent person stationed at the surface of the trench to warn workers in the trench of danger and to provide emergency help? - Is the trench a confined space, and are the requirements of the confined space program met?…

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BEGIN Excavation INSTRUCTION ZONE ROADWAY SAFETY 1 # Why Are Trenches Dangerous? A trench is an excavation deeper than it is wide. ## Trenches can kill • Workers can be buried alive - Cave-ins can result from stresses in walls, nearby moving vehicles and equipment, or spoil piles - Water can collect in bottom - Flammable/toxic gases can build up - Gas from nearby sewer or gas lines can seep into trench Trenches > 4' deep may be confined spaces. ## Before digging - Call electrical, gas, and communications utilities - Use extreme caution with equipment NAPA ARIBA An excavation with formwork 15' or less from a sidewall is also a trench.