Safety Talk: Site Conditions and Trench Safety

Site conditions are a very important factor in the safety of an excavation. The Competent Person is required to perform inspections daily or as conditions change to identify hazards.

A Competent Person must complete a soil test before work begins to determine the stability of the soil.  Type A- Most stable. Clay, silty clay, and hardpan.  Type B- Medium stability. Silt, sandy loam, medium clay, and unstable dry rock.  Type C- Least stable. Gravel, loamy sand, soft clay, submerged soil, or dense, heavy unstable rock.

The Competent Person must test for oxygen levels and the presence of hazardous fumes and gases before workers enter the trench. If oxygen levels are less than 19.5 percent or other hazardous atmospheric conditions exist, precautions such as ventilation and/or respiratory protection must be used to protect workers.
Atmospheric testing should be increased if gas-powered equipment is being used in the trench or if welding, cutting or burning is done in the trench.

The location of underground utilities should be identified and shut off before work begins. Per OSHA regulations, underground installations should be protected, supported, or removed.

There are specific shoring and protection requirements when there is a potential for water accumulation in an excavation. Protection requirements also include monitoring by a Competent Person, water removal to control levels of accumulation, and providing emergency rescue equipment such as lifelines and harnesses.

Weather conditions should be monitored particularly for rain, snow and any conditions that will affect water accumulation, soil conditions, or visibility on the site, such as fog.

Mobile equipment should have warning systems when used near excavations, and barricades should be used to protect workers in the trench. Surface encumbrances such as equipment, materials, boulders that could cause a hazard to workers should be removed.
If you notice a change in the site’s condition, what should you do? INFORM YOUR SUPERVISOR/ COMPETENT PERSON.