Trench and Excavation Safety

Originally published 07/12/2017

Trench collapses can occur without warning, regardless of the depth. The vast majority of trenching fatalities occur in trenches 5 to 15 feet deep. But trench cave-ins don’t have to happen. They are preventable with proper planning and execution of safety precautions.

Here are some practices that will help reduce the risk of on-the-job injuries or fatalities on excavation sites.

  1. Know where the underground utilities are located before digging.
  2. Keep excavated soil (spoils) and other materials at least two feet from trench edges.
  3. Keep heavy equipment away from trench edges.
  4. Identify any equipment or activities that could affect trench stability.
  5. Test for atmospheric hazards such as low oxygen, hazardous fumes, and toxic gases when workers are in trenches more than four feet deep.
  6. Inspect trenches at the start of each shift. This should be done by the competent person. The competent person should be authorized to order immediate corrective action, including restricting entry into the excavation, until any hazards or potential hazards have been eliminated.
  7. Ensure that employees working in trenches four feet deep or more have an adequate and safe means of exit, such as ladders, steps or ramps. These must be within 25 feet of all workers at all times and will need to be relocated as the job progresses.
  8. Inspect trenches following a rainstorm or other water intrusion.
  9. Inspect trenches after any occurrence that could have changed conditions in the trench.
  10. Do not work under suspended or raised loads or materials.
  11. Ensure that workers wear high-visibility or other suitable clothing when exposed to vehicular traffic.
  12. Develop a trench emergency action plan and train workers and supervisors on the proper actions to take in case of an emergency.

Remember: Unlike most accidents, the cave-in of an excavation can usually be predicted if closely watched. So stay alert. Don’t take anything for granted.

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The Hazards of Leading Edges – Part II: Excavation

This week we’ll look at leading edge hazards in excavation work. OSHA regulates hazardous elevations starting at 48 inches (four feet) in general industry, and 72 inches (6 feet) in construction. However, proactive safety management programs look for leading edge hazards at any height and create plans to protect workers.

The leading edge of an excavation project poses several potential injury scenarios, including falls and cave-ins. The danger to workers and equipment is great if the edge warning is limited or non-existent. Devastating impact injuries occur from falling into excavation holes, especially if the worker lands on an object, such as a concrete pipe or concrete forms.

Never pile excavated material (spoils) too close to the edge of a trench/excavation. It obscures the view of the edge, which makes it possible for equipment to drive off the edge and into the excavation.

Soil at the leading edge of an excavation site has a low, unconfined compressive strength, meaning the soil does not have anything to push against when it is compressed. An edge with low compressive strength can result in the soil giving way, and anyone or anything at that edge will cascade into the hole.

Provide leading edge protection on an excavation site by doing one or more of the following:

  • Use snow fencing or other visual warning material to create a warning barrier.
  • Set spoils and equipment at least two feet from the excavation.
  • Where the site does not permit a two-foot set back of materials, temporarily haul spoils to another location.

Leading edges exist in all types of construction. Make sure your jobsite safety audit includes an inspection of all leading edges and provides a plan of action for protecting workers.