802 Trench and Excavation Safety

Sloping and Benching Problems

Although sloping and benching is a good method for excavations, there are still some problems you may encounter.

For example wide excavation areas can:

• expose footings or cause damage to the walls of the adjacent structure and pose additional hazards to employees;
• expose or place utilities (such as electrical power, water, and gas lines) above the angle for a safe slope; and
• cause damage from the movement of the equipment across a larger excavation.

To prevent the collapse of an unsupported bench in an excavation 8 feet or less in depth, the allowable height of a bench at the base of an excavation must be 3 1/2 feet or less. A common hazard in a multiple-benched excavation is the collapse of one bench into a lower bench.

Preparing to Slope or Bench

Before the start of sloping or benching, the contractor needs to:

• determine soil types at the excavation site using the soil classification system;
• consider potential sloping and benching problems; and
• identify all protective measures necessary to ensure safe working conditions, and
• determine which protection method is the best to use at the site.

Knowledge Check Choose the best answer for the question.