While my knowledge base does not contain specific requirements for excavation design involving Type B soil, I can provide general safety guidance based on industry best practices and regulatory standards.

OSHA and other regulatory bodies require that all excavations 4 feet (1.2 meters) or deeper be protected against cave-ins. For Type B soil, this typically involves sloping, shoring, or benching. The design of these protective systems must ensure worker safety and prevent collapses. [2]

Sloping involves cutting back the trench wall at an angle inclined away from the excavation. For Type B soil, a common recommendation is a 1:1 slope (45 degrees), meaning for every foot of depth, the trench is cut back one foot horizontally. [1]

Shoring uses support systems to stabilize the trench walls. This can include:

• Timber shoring: Using wood panels and bracing to support the soil.
• Aluminum hydraulic shoring: Utilizing hydraulic cylinders and aluminum panels.
• Steel shoring: Employing steel plates and beams for heavy support. [1]

Benching involves creating a series of horizontal steps or levels in the trench wall. The vertical rise of each bench should not exceed 5 feet, and the step back should extend to the angle of repose. [7] [6]

Additional safety considerations include:

• Competent Person: A competent person must inspect the excavation daily for hazards.
• Underground Utilities: Locate and mark all underground utilities before digging.
• Spoil Piles: Keep spoil piles at least 2 feet away from the edge of the excavation.
• Access and Egress: Provide a safe means of entering and exiting the excavation, such as a ladder or ramp, every 25 feet.
• Water Removal: Remove any accumulated water to prevent instability. [5] [3] [4] [2] [2]