Can You Dig It? The Basics of Trenching Safety

Excavations and trenches have become so commonplace on work sites that some employers and employees have developed a sense of complacency with some of the most basic requirements of excavation safety. To counter this, the Occupational Safety and Health Administration initiated a National Emphasis Program on Trenching and Excavation on Oct. 1, 2018, to increase OSHA's education and enforcement efforts regarding trenching and excavation operations. Under this NEP, OSHA compliance officers can inspect trenching operations whenever they observe an open trench or excavation, regardless of whether there is a violation.

OSHA's excavation standard[1] contains the requirements for excavation and trenching operations. The standard applies to all open excavations, including trenches. An excavation is any man-made cut, cavity, trench, or depression in the Earth's surface formed by earth removal, and a trench is a narrow excavation made below the surface of the ground.

Trenching and excavation work continues to be hazardous. With an increased risk of deaths and serious injuries resulting from trenching and excavation incidents, a review of OSHA's trenching and excavation requirements can be useful.

OSHA Believes There is a Potential for Collapse in Virtually All Excavations
While cave-ins pose the greatest risk in any trenching or excavation operation, there are other hazards associated with these projects, including falling loads, hazardous atmospheres, and hazards from mobile equipment, and are the focus of OSHA's excavation standard. Under the standard, there are several tasks that must be performed by a competent person, such as classifying soil, inspecting protective systems, designing structural ramps, monitoring water removal equipment, and conducting site inspections. OSHA's standards define a competent person as an individual designated by the employer who can identify existing and predictable hazards in the surroundings or working conditions that are unsanitary, hazardous, or dangerous to workers and who is authorized to take prompt corrective measures to eliminate them.

OSHA Has Requirements to Prevent Cave-ins
OSHA's excavation standard contains several requirements regarding sloping and benching the sides of an excavation, supporting the sides of the excavation, or placing a shield between the side of the excavation and the work area to prevent cave-ins. Sloping the sides of the excavation to an angle not steeper than one-and-a-half by one means for every foot of depth, the trench must slope back one-and-a-half feet. Designing a protective system requires consideration of many factors, including soil classification, depth of cut, water content of soil, weather and climate, and other operations in the area; it typically involves using a trench box or shield approved by a registered professional engineer.

The standard also requires support systems for structures adjacent to an excavation, such as buildings, walls, sidewalks, and pavements, so they remain stable. Any protective systems used must be maintained free from damage and safety defects.

However, the excavation standard does not require a protective system when an excavation is made entirely in stable rock or when an excavation is less than 5 feet deep and a competent person has examined the ground and found no indication of potential cave-in.

Protect Workers from Loose Material Rolling Into an Excavation
The excavation standard also requires protecting employees working within an excavation or trench. Employers must prevent employees from working on the slopes of the excavations above workers within the excavation. Employers also must prohibit employees in the trench from working under suspended loads and must keep materials and equipment at least 2 feet from the edge of the excavation.

Prevent Water from Accumulating in an Excavation
Water can undermine the sides of an excavation and contribute to or cause a trench collapse. OSHA's excavation standard requires the use of a pump to remove water or control water accumulations. In addition, a competent person must monitor any water removal equipment. Drainage from the excavation must be maintained, and employers can use diversion ditches or dikes to prevent surface water from entering the excavation. A competent person should inspect excavations after heavy rains.

Test Hazardous Atmospheres Inside Excavations
Atmospheric testing is required in excavations deeper than 4 feet where oxygen deficiencies or hazardous atmospheres are present or could reasonably be expected. The excavation standards require employers to prevent employee exposure by using proper ventilation and respiratory protection. If there are hazardous atmospheres present in an excavation, emergency rescue equipment, breathing apparatus, and a safety harness and line must be used. In some instances, there could be a confined space or permit-required confined spaces in an excavation.

Follow Access and Egress Standards
OSHA's excavation standard requires ladders, steps, ramps, or other safe means of egress for workers working in a trench deeper than 4 feet, and they must be located 25 feet or less from workers in the excavation. Any access or egress must be designed by a competent person.

Conduct Site Inspections
The excavation standard requires competent persons to examine excavations, adjacent areas, and protective systems. These examinations should be conducted daily and prior to starting work and as work is performed, if conditions change.

OSHA's excavation and trenching standard can be found on its website, as can a number of memorandums and notices regarding excavation and trenching safety.

Christopher Peterson is an attorney with the labor and employment law firm Fisher Phillips.

[1] 29 CFR Part 1926, Subpart P

Posted on Jun 18, 2019