How deep does an excavation need to be before sloping is required?

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# WEATHER (cont.) ## INVESTIGATION (cont.) Kentucky FACE Program 16KY017 Page 6 special response unit from the fire department arrived to recover the construction worker. He was recovered at 10:52 am and was unresponsive. The coroner pronounced the victim dead at the scene at 10:52 am. ## Lack of Trench Protective System Performance of a soil test and an adequate trench protective system could have prevented this incident. OSHA requires that all workers in trenches 5 feet or more in depth be protected by sloping, shoring, or the use of shields. Since the soil was a mixture of class B and C soils, the soil should have been classified as class C soil. Trench excavation with class C soil requires sloping at 1½ H:1V (or 34°), meaning that the soil needed to be cut back 1½ ft. for every 1 ft. of depth (Figure 5). Given the proximity of the trench to the concrete wall, it was impossible to achieve the necessary slope on both sides of the trench. Since the concrete wall made conventional sloping techniques impossible, a trench box or shoring system should have been installed prior to allowing entry into the trench. The excavation operator commented that he was to bench the road-facing side of the trench. However, OSHA requires that type C soil be sloped and never benched. Furthermore, sloping and benching techniques must be applied to both sides of the trench to be effective. The side of the trench facing the concrete wall was the side that was most unstable and suffered the fatal collapse. Type C Soil Vertical 112:1 34 Degrees Horizontal Figure 5. OSHA sloping requirements for type C soil. This method would not have been possible due to the proximity of the trench to the concrete wall. <table><tr><th colspan="3">OSHA Sloping Requirements</th></tr><tr><td>Soil Type</td><td>Slope</td><td>Angle (degrees)</td></tr><tr><td>A</td><td>3/4H:1V</td><td>53°</td></tr><tr><td>B</td><td>1H:1V</td><td>45°</td></tr><tr><td>C</td><td>112H:1V</td><td>34°</td></tr></table>

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# Trench and Excavation Safety Trench collapses, or cave-ins, are the leading hazard in excavation work. Safe trenching helps prevent falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. ## Trench Safety Measures Trenches 5 feet or deeper require a protective system unless dug in stable rock. For trenches less than 5 feet, a competent person must decide if protection is needed. Trenches 20 feet or deeper must have a protective system designed or approved by a registered professional engineer, as required by OSHA 1926.652(b) and (c). ## Competent Person Before workers enter a trench, a competent person must inspect it daily and after any condition changes to ensure safety. This person is trained to identify hazards, determine soil types, select protective systems, and has the authority to correct issues immediately. ## Access and Egress • Keep heavy equipment and spoils at least 2 feet from trench edges - Locate underground utilities before digging • Test for atmospheric hazards in trenches over 4 feet deep • Inspect trenches daily, at the start of each shift, after storms, and after conditions change • Never work under suspended loads - Wear high visibility clothing when near traffic # Protective Systems • Benching: a method of protecting workers from cave-ins by cutting the sides of an excavation into horizontal steps. Benching is not allowed in Type C soil. • Sloping: involves cutting back the trench wall at an angle inclined away from excavation. • Shoring: requires installing aluminum hydraulic or other types of supports to prevent soil movement and cave-ins. • Shielding: protects workers by using trench boxes or supports to prevent cave-ins. Designing these systems can be complex, as factors like soil type, trench depth, moisture, weather, nearby loads, and site activity must all be considered. OSHA standards require that employers provide workplaces free of recognized hazards. The employer must compl…