Safety Tip: What to Know About Trenches

Excavator on jobsite

Trench collapses can trap workers under thousands of pounds of dirt in just seconds, and collapses kill two workers every month. By late June of 2025, 11 trench-related fatalities had already occurred that year, prompting OSHA to issue a statement urging safe trenching practices. 

Not long ago, 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. There was no means of quick escape and excavated earth was closer than two feet away from the hole.

Trench Safety

One cubic yard of soil can weigh as much as a car, so it is important to know and test the type of soil before beginning any work. Rain can compact soil and significantly increase the weight, causing it to become even more hazardous and likelier to collapse.

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.

Here’s advice from OSHA on trenching safety:

Never enter a trench unless:

  • It has been properly inspected by a competent person.
  • Cave-in protection measures are in place.
  • There is a safe way to enter and exit.
  • Equipment and materials are away from the edge.
  • It is free of standing water and atmospheric hazards.

Prevent trench collapses:

  • Trenches 5 feet deep or greater require a protective system.
  • Trenches 20 feet deep or greater require a protective system designed by a registered professional engineer.

Protective systems for trenches:

  • SLOPE or bench trench walls by cutting back the trench wall at an angle inclined away from the excavation.
  • SHORE trench walls by installing aluminum hydraulic or other types of supports to prevent soil movement.
  • SHIELD trench walls by using trench boxes or other types of supports to prevent soil cave-ins.

How to Prevent Cave-ins:

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.

  • 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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