Canadian Occupational Safety

AUGUST/SEPTEMBER 2017 25 these to the workers. When an area has been identifi ed as a confi ned space according to the regulatory criteria, the employer is required to fulfi ll certain obligations specifi c to confi ned spaces, says Jon Wright, EHS specialist at Waterloo, Ont.-based Acute Environmental and Safety Services. Some of these are tasks that must be completed before a worker is required to enter the space. First, an employer must have a qualifi ed person assess the site for haz- ards. The assessment is used to then create a plan that states all precau- tions, controls and personal protective equipment needed to render the area safe for the worker. In some provinces, including Ontario and Manitoba, reg- ulations require the employer to have an entry permit; it serves as a check- list to verify everything in the plan has been put in place. The plan must include an effective rescue, Wright says. "If something goes wrong, what people and equipment do we need on the project site to get the person out as fast as possible? The rescue has to be ready for immediate implementation." At Edmonton-based PCL Construc- tion, anytime they have to go 6 inches under the soil, a ground disturbance permit must be completed, says Eugene MacMahon, district health, safety and environmental manager. The permit system establishes roles and responsi- bilities and helps them determine if an excavation is a confi ned space. "It establishes the level of risk before anyone goes anywhere near the ground. We'll fi nd out who's doing it, what drawing they're using, where it is and when it's going to start. We get a competent person to fi ll out this checklist. They'll determine what kind of soil it is. Or are you breaking rock? Is it close to buildings, footings or pilings? Is there a source of vibra- tion nearby, like traffi c? And have the utilities been located? Depending on where you are, you might have an explosive atmosphere around the excavation," he says. Using the permit, they also deter- mine what controls they need. They consider the slope on the excavation; the size of the excavation and whether they need to re-route traffi c; whether water removal operations will be needed; where the hoisting equipment should be placed; and how to vent exhaust away from the excavation. "This gives us a lot of informa- tion to determine: Are we looking at a confi ned space situation here? If you're going 2 feet down, it's hard to call something a confi ned space. But if you're going 80 feet down, as we did in downtown Edmonton, it makes a difference. How do you rescue some- one from 80 feet underground? It's a tough thing. All the hazards there are combined with the confi ned space," MacMahon says. As soon as an area space has been identifi ed as a confi ned space, precau- tions against hazardous atmosphere must be taken. Prior to entry, the qual- ifi ed person should test the air in the space. Then there should be continu- ous monitoring and ventilating while workers are in the space. At PCL, MacMahon says, with areas deemed confi ned spaces, they typically have the workers wear a four-head gas monitor, which monitors oxygen, LEL, methane and H2S. "You can have naturally occurring H2S, especially if you've had an open excavation for a long time and you've brought in vegetation." In some exca- vations, he adds, they will send down gas detection systems that can be oper- ated remotely from above. Safety managers should also deter mine whet her t here are underground utilities in the digging area, Gursky says. Remember, line locates show approximate locations. Specifi c locations may have to be found by hydro-vacing or digging by hand. When the locations are known, the safety manager must determine the control zone, or safe area, in relation to the specifi c utility. Cave-ins can be prevented through the use of sloping (or benching) and shoring. Sloping entails cutting back the trench walls at an angle slanted away from the excavation. Shoring systems consist of vertical planks placed against the excavation walls and held apart by shoring screws or hydraulic jacks. The structure, called a "shoring cage," is usu- ally of wood, aluminum or steel. "The cage is engineered to hold back the soil in the event of a collapse. They are all engineer-certifi ed, and you can't modify them without approval from a certifi ed engineer," Gursky says. "Depending on the depth of the exca- vation, you may need to stack them a few times. They need to be at least a foot above the top of the excavation." Other controls include: • installing an adequate number of exit ladders • removing water from the excavation • protecting workers from falling into the excavation • replacing equipment to reduce carbon monoxide risk. Once the location is identifi ed as a confi ned space, everyone involved in the work needs to be adequately trained, Wright says. Workers need to know what procedures they should be following, what could go wrong and how they must respond in an emergency. Practise the rescue plan so everyone is sure of their role. In Ontario, the rescue team must be trained in the procedure to be used, safe operation of any equipment deemed necessary in the plan (such as a breathing apparatus) and fi rst aid, including CPR. Generally, confi ned space regulations require another standby worker be stationed above ground to provide rescue and watch for danger. Workers should also be aware they have a right to a gas moni- tor and rescue plan. In the basement excavation, all fi ve workers exposed to the toxic air were fi ne in the end. Ventilation systems were installed and the work contin- ued. Serious incidents like this happen all the time, Kossey says. "I don't think people recognize what's happening. In this case, there was very limited air fl ow and all the nitrogen dioxide. They had three excavators in the space and they had a large number of plate packers and cut-off saws running. So they had many pieces of equipment without enough ventilation," she says. "Nobody recognized the hazards." Linda Johnson is a freelance journalist based in Toronto. She can be reached at lindajohnson@sympatico.ca In British Columbia, enclosed spaces that are not considered "confi ned spaces" must satisfy specifi c exclusion criteria. The spaces that may be excluded from Part 9 Confi ned Spaces of the Occupational Health and Safety Regulation, provided that all the below criteria are met, include swimming pools; crawl spaces under school portables or other non-industrial buildings; excavations; attic space; open, unconnected wet wells or dry wells for storm or sewer hookups at new construction sites; elevator shafts; HVAC plenums; and agricultural feed mixer wagons and trucks that are permanently open on top and empty. EXCLUSION CRITERIA: • The design, construction, location and intended use of these spaces will ensure these spaces are characterized by clean respirable air at all times. • The space must have an interior volume of not less than 64 cubic feet per occupant. • The space must have openings to the atmosphere that are known to provide natural ventilation. • There must be no potential for a high or moderate hazard atmosphere, as defi ned in section 9.1 of the regulation, to exist or develop immediately prior to any worker entering the space or during any work within the space. • There must not be a need to mechanically ventilate, clean, purge or inert the space prior to entry for any reason. • There must be no potential for a hazardous substance to migrate through any media (such as soil, conveyance, piping or structure) to infi ltrate the space. • The space must be free of residual material (such as water, sludge or debris) that if disturbed could generate air contaminant that could immediately and acutely affect a worker's health. • No risk of entrapment or engulfment to workers entering the space. • The space must not contain, have introduced or be adjacent to tools, equipment or processes that could generate air contaminants that could immediately and acutely affect a worker's health. Source: WorkSafeBC ENCLOSED but not CONFINED

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