Cave-ins pose the greatest risk and are much more likely to result in a worker-related fatality than other excavation-related accidents. An unprotected trench becomes an early grave for a lot of workers. The weight of collapsing soil and the speed in which it is traveling cannot be overstated.

Trench Safety Measures

As soon as a trench reaches the 5’ depth, whether it appears stable or not, the OSHA standard governing excavations becomes applicable and a protective system must be installed. The only exception is for trenches dug in stable rock. If shallower depth trenches show signs of instability, these must be supported as well.

Competent Person

OSHA requires the Competent Person to perform a daily inspection of the trench and its immediate surroundings. A re-inspection is required should conditions change that could have a direct bearing on the conditions of the trench. Among other things, this individual has knowledge of the standard, knowledge of the work being performed and the ability to take prompt corrective action to ensure worker safety.

Access and Egress

OSHA standards require safe access and egress to all excavations. This includes ladders, ramps or other safe means of exit for employees working in trenches 4’ or deeper. The travel distance to reach these devices cannot exceed 25’.

General Rules

.  Spoil piles must be kept, at minimum, 2 feet from trench edges

.  Underground utilities must be located prior to digging

.  Surface encumbrances must be supported or removed if undermined

.  Atmospheric Testing is required where poor air quality is suspected

.  Workers are not permitted under overhead loads

.  Workers must wear high-visibility clothing, when exposed to vehicular traffic

Protective Systems

Benching…means a method of protecting workers from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near vertical surfaces between levels. Benching cannot be done in Type C-soil.

Sloping…involves cutting back the trench wall at an angle inclined away from the excavation.

Shoring… requires installing aluminum hydraulic or pneumatic shoring devices to prevent soil movement and cave-ins.

Shielding…protects workers by using trench boxes or shielding devices

Tabulated Data

These are a special set of instructions in which the installation requirements of the protective system are dictated by both the manufacturer and the Registered Professional Engineer who approved the design. Tabulated Data must possess the engineering stamp from the RPE approving the design. Tabulated Data is required to be present on the jobsite during installation of the system.

Prospan tabulated data is available on our website at