Trenches and excavations can present hazards that are sometimes overlooked on residential construction sites. Being caught in a trench or excavation cave-in is one of the leading causes of fatal injuries in the construction industry. 

Some of the most common hazards that result in workers being injured during trenching and excavation work:

• Cave-ins of the soil on a side wall of an excavation occur quickly — in one to three seconds — and there is generally no time for a worker to respond and escape safely.
  
  
• The atmosphere in excavations can turn deadly when oxygen is displaced by other hazardous gasses.
  
  
• Materials falling into excavations can strike workers and cause serious injuries.
  
  
• Water accumulation in excavations can weaken walls and lead to cave-ins.
  
  
• Damaged underground utilities can expose workers to hazardous or explosive atmospheres, electrocution or drowning.

It is important to never enter an unprotected trench. Each employee in a trench over 5 feet in depth must be protected from a cave-in by an adequate protective system. Some protective systems include:

• Sloping for stability, at a minimum slope of 34 degrees in Type C soil
  
  
• Benching to create steps (allowed in Type A and Type B soil only)
  
  
• Shielding with a trench box or shoring to protect workers in a trench

When working in trenches or excavations, a competent person must determine the soil type and identify and correct any hazards before workers may enter a trench. The competent person must also continue to conduct regular inspections to ensure the safety of the workers inside the trench or excavation.

For more information on trenching and excavation safety, check out NAHB’s Trenching and Excavation Safety Card on "Trenching Hazards in the Home Building Industry." The popular "NAHB-OSHA Trenching and Excavation Safety Handbook” is also available for purchase at NAHB BuilderBooks.

For more information, e-mail Marcus Odorizzi at NAHB, or call him at 800-368-5242 x8590.