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Safety Tip: What to Know About Trenches

Industrial / Construction, Safety Tips

Recently, a construction firm in Lebanon, Missouri faced a fine of nearly $200,000 for allowing two workers to enter a trench without any type of safety precaution in place, including not having any means of quick escape, or keeping the excavated earth at least two feet away from the hole. Trench collapses can trap workers under thousands of pounds of dirt, and they kill two workers every month.

Trench Safety

Any trench that is at least five feet deep must have protective measures in place unless they are dug into solid rock. Any trench four feet deep or less must be evaluated by a competent person to determine if they require protective measures. A competent person should also inspect the trench daily to determine if conditions have changed.

When done safely, trenching operations can limit worker exposure to cave-ins, falling loads, hazardous atmospheres, and hazards from mobile equipment. The best way to prevent a trench collapse is to slope or bench trench walls, shore trench walls with supports, or shield trench walls with trench boxes.

How to Prevent Cave-ins:

  • Benching – is a method of leveling off the trench as it goes further down, so that it resembles a series of stair steps, however this method does not work in all types of soil.
  • Sloping – is the procedure of digging diagonally into the sides of the trench, so that the walls are angled outward.
  • Shoring – involves placing support beams across the trench along its width.
  • Shielding – expands upon this idea with the Trench Box, a type of support beam permanently bonded on both ends to slabs of metal that effectively cut the workers off from the trench walls.

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