Trench Excavation

Trench excavation safety procedures are essential to prevent cave-ins and ensure worker safety. OSHA regulations require the use of protective systems in excavations to protect employees from cave-ins, except when excavations are made entirely in stable rock, or are less than 5 feet in depth and a competent person has examined the ground and found no indication of a potential cave-in [8]

The two basic methods of protecting workers against cave-ins are sloping and temporary protective structures like shoring and trench boxes. [2]

Sloping involves cutting back the trench wall at an angle inclined away from the excavation, with the angle depending on soil conditions. [2]

Shoring systems support the sides of an excavation using materials like aluminum, steel, or wood panels supported by screws or hydraulic jacks. Wherever possible, shoring equipment should be installed as the excavation proceeds, and if there is any delay between digging and shoring, no one should enter the unprotected trench. [2]

Trench boxes or shields are structures that can withstand the forces of a cave-in and protect workers inside. [1]

Before beginning an excavation, it's important to check for potential hazards, test for hazardous gases and oxygen levels, ensure appropriate PPE is used, have a worker above ground to warn of danger, and have a means of exit no more than 8m (25 ft) away from any worker in the trench. [7]

Excavated material must be kept back a minimum distance of 60 cm (2 ft) from the edge of a trench excavation and 1.2 m (4 ft) from any other excavation. [5]

Support systems shall be installed and removed in a manner that protects employees from cave-ins, structural collapses, or from being struck by members of the support system. Removal shall begin at, and progress from, the bottom of the excavation. [3]

Water must not be allowed to accumulate in an excavation if it might affect the stability of the excavation or might endanger workers [9]

For trenches more than 1.2 metres deep, a worker must be protected from cave-ins or sliding material. [6]

If workers are required to enter a trench over 1.2 m (4 ft) deep, the safe point of entry and exit must be located within 8 m (25 ft) of the workers and the excavation must be safely supported or sloped to the entry and exit location. [5]

A temporary protective structure in an excavation more than 3 metres deep must be designed and certified as safe by a professional engineer [6]

Shoring or manufactured or prefabricated support systems must be installed in firm contact with the faces of the excavation, and in a manner which ensures no loss of soil from behind or below the bottom of the shield or shoring while the excavation is open. [4]

Voids between the shoring and the excavation face must be backfilled or blocked. [4]

Shoring materials must be installed from the top down and removed in reverse order. [4]

Workers must not enter an excavation to remove shoring materials if ground conditions have deteriorated SO as to make entry for shoring removal unsafe. [4]

If the average depth of a spoil pile which is adjacent to a supported excavation exceeds 60 cm (2 ft), the selection of the shoring or shielding must take into account the resulting increase in lateral soil pressure. [5]

The sides of an excavation must be scaled and trimmed or otherwise stabilized to prevent slides of material or falls of rock which could endanger workers. [5]

If an excavation is a hazard to workers, it must be effectively covered or guarded. [5]

Safe means of entry and exit must be provided for an excavation a worker enters. [5]

A walkway across an excavation must be at least 50 cm (20 in) wide, and if crossing an excavation over 1.2 m (4 ft) deep, be equipped with guardrails, meeting the require- ments of Part 4 (General Conditions), on both sides. [5]