Trenching and Excavation Safety

Key points

  • Workers should never work in an unprotected trench.
  • A trench can collapse or cave-in at any moment.
  • Without a protective system in place, a trench collapse can crush and suffocate workers.
Trench with a yellow ladder.

Overview

Working in an unprotected trench is dangerous. The walls can collapse suddenly and without warning. When this happens, workers do not have time to move out of the way.

While a small amount of dirt may not seem dangerous, one square yard of dirt can weigh more than 3,000 pounds. This weighs the same as a compact car. This small amount of dirt is enough to fatally crush and suffocate workers.

Injuries and deaths related to trench collapses continue to happen. From the years 2003 to 2017, there were a total of 373 trenching deaths. More than 80% of those deaths happened in the construction industry. Workers do not often survive trench collapses, but we can prevent them.

A construction site with a trench.
Workers use a trench box to shield the trench against collapse.

Keeping workers safe

There are ways to prevent trench collapses. Engineering controls, protective equipment, and safe work practices can reduce hazards to workers and prevent trench cave-ins.

Workers should never enter a trench that does not have a protective system in place.

A competent person should design and install the protective system. A competent person can find hazards and correct them.

Workers can take training to become a competent person. Training is available from many sources, including:

  • insurance companies,
  • trade associations,
  • labor unions, and
  • companies that make safety equipment for trench workers.

Preventing trench collapses

Planning

To prevent trench collapses, employers should plan by doing the following before the job begins:

  • Assign and train a competent person
  • Evaluate the soil to determine its stability
  • Call 811 to identify and mark underground utility lines
    • Dig a minimum of 5 feet away from utility lines
  • Identify safe locations for spoil piles and heavy equipment routes
  • Determine trench depth and
    • Set up a protective system if the trench will be 5 feet or deeper
    • Provide engineering protections if the trench will be 20 feet or deeper
  • Have a traffic control plan and lane closure permits
  • Develop a trench emergency action plan

OSHA Standard

The OSHA standard for excavations, including trenches, is 29 CFR* 1926 Subpart P . This standard de­scribes the precautions needed for safe excavation work. OSHA requires that all excavations 5 feet deep or great­er make use of one of the following pro­tective system options:

  • Sloping the ground
  • Benching the ground
  • Shoring the trench with supports (such as planking or hydraulic jacks)
  • Shielding the trench (using a trench box)

Other Methods

The best way to prevent trench collapse and trenching-related deaths is to use other methods when possible. Some other options include:

  • Directional boring
  • Relining the pipe
  • Pipe ramming
  • Utility tunneling or pipe jacking

Robots can be used on construction sites to transport, line, and join large pipes to protect workers from serious injuries. Robots may reduce the need for pipe layers and other helpers to work at the bottom of the trench.

Construction workers digging in a trench.
Planning is required before a job starts. Before you dig it, plan it!

Programs and initiatives

Did you know?‎

Trench Safety Month Takes Place Every June!


The National Utility Contractors Association has declared June Trench Safety Month. The Trench Safety Stand Down will take place each June. This event will highlight innovative educational and safety programs for worksites.

Did you know?‎

Every April you can participate in or host a National Stand-Down to Prevent Struck-by Incidents. This event will allow you to learn more about work zone safety, lift zone safety, heavy equipment, and dropped objects.

Resources

NIOSH Publications

Development of Draft Construction Safety Standards for Excavations
Workshop input and an analysis of the suggestions and commentary produced by the workshops.
Cover image of Alert 85-110
Preventing Deaths and Injuries From Excavation Cave-Ins
Standards and recommended work practices to avoid death and injury from excavation cave-ins.
document cover
Preventing Worker Deaths from Trench Cave-ins
Recommended engineering controls, protective equipment, and safe work practices to reduce hazards.

Fatality Assessment and Control Evaluation (FACE) Reports

Review trenching related NIOSH FACE and State FACE reports for recommendations to prevent similar deaths in CDC Stacks.

View by Collection (NIOSH/FACE) or search for reports using keywords in the search bar.

Infographic

Trench Safety: Before you did it, plan it! Infographic [en español]

Science Blog

Preventing Trenching Fatalities

Describes the risks construction workers face when working in trenches.

Learn more ‎

NIOSHTIC2 is a searchable bibliographic database of occupational safety and health publications, documents, grant reports, and journal articles supported in whole or in part by NIOSH.
Trenching related search results

OSHA Resources

CPWR - Center for Construction Research and Training Resources

Webinars

Increasing Awareness of Factors that Influence Trench Safety - Learn about recent trends and a collaborative effort to increase awareness of the factors that may contribute to trenching incidents and ways to mitigate the risks. Download Presentation Slides

OSHA and American Society of Safety Professionals Share Trenching Safety Webinar - Learn how contractors and workers can conduct excavation and trenching operations safely by following subparts of 29 CFR 1926, as well as the best practices described in industry consensus standards such as ANSI/ASSP A10.12.

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Content Source:
National Institute for Occupational Safety and Health