Em385 1-1 Treanch depth

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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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TENSIN MASSACHUSETTS DEPARTMENT OF LABOR STANDARDS # Trench Hazard Alert MASSsafety Works! Workplace Safety is No Accident Every year, workers are killed or seriously injured conducting work in trenches, including utility repair, utility inspections, and construction. Trenches are recognized by OSHA as one of the most hazardous construction work conditions, with a fatality rate more than double that for construction work overall. ## Requirements for Trench Work • Protect workers from soil cave-ins in all trenches 5' or deeper, and in shallower trenches where a cave-in hazard exists. Do this by supporting the walls with shoring, shielding workers with trench boxes, or sloping the walls back wide enough, in accordance with the OSHA Excavation Standard. • Provide ladders to workers in trenches 4' or deeper. • Underground utilities must be identified and supported. Call Dig Safe at 1-(888) 344-7233. • Ensure that workers wear high visibility clothing when exposed to vehicle traffic, and use appropriate work zone signage and traffic channeling set-ups. . Spoils must be kept back a minimum of 2' from the trench edge. Keep equipment and heavy material as far back from the trench edge as possible. • Stabilize undermined adjacent structures. • Protect employees from water accumulation by pumping out ground or utility water, and preventing drainage or other water from entering the trench. • Do not allow employees to work under suspended or raised loads or materials. • Conduct pre-job planning and inspections of trench worksites. A competent person must inspect each trench worksite, including the soil protective system, prior to the start of work, and again if there is a hazard-increasing change in conditions such as a rainstorm. Unsafe trenches are dangerous! Trenches more than 20 feet in depth must be designed by a registered professional engineer. ## Workers in trenches face other significant hazards in addition to cave-in of the soil walls, including: . …

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# Requirements for Protective Systems {Division 3/Subdivision P 29 CFR 1926.652} (cont.) ## Selection of Protective Systems (cont.) This material is for training use only # Protective Systems [29 CFR 1926.652(a)] Excavations and trenches less than five feet deep must still be sloped, benched, or otherwise supported when a Competent Person determines there is indication of cave-in. a Be careful not to get caught up on just the five foot depth requirement. Consider work practices in a shallow trench as well (i.e. working hunched over or on hands and knees). ## Selection of Protective Systems Protective systems are divided into two categories and include four choices in each: 1. Sloping and benching systems; and 2. ...everything else. The basic systems for protecting employees from cave-ins are sloping, benching, shoring, and shielding. The system that you should use depends on factors such as soil type and water content, excavation depth and width, the nature of the work, and nearby activities that could increase the risk of a cave-in. The competent person has the responsibility for considering these factors and for determining the appropriate protective system. A registered professional engineer must design protective systems for all excavations that are more than 20 feet deep. (from OR-OSHA's publication titled, “Excavations” Pub. #440-2174 (6/06)). OR-OSHA 302 Excavation Safety 24