Categories: Construction, Safety

Excavating Accidents

TASA ID: 1092

OSHA states that workers have a right to a safe and healthy work environment, including construction workers handling excavations in trenches.  A trench is a type of excavation or depression in the ground that is generally deeper than it is wide (as opposed to a wider gully or ditch) and narrow compared to its length (as opposed to a simple hole). Trenches are used on many construction sites to lay pipe, cables and conduits among other reasons.

Trenching work is hazardous; trenches and excavations can collapse, burying workers. A cubic yard of soil weighs about one ton, i.e., 2,000 pounds.  This comes from the FAQs on American top soil.  So even one cubic yard of soil falling on a construction worker can be highly dangerous. 

The Bureau of Labor Statistics found that in a recent year, there were over 5,000 deaths annually due to construction site-related accidents, many of which were trenching related. Many construction jobs need trenching to do such things as put in sewer lines, electrical wires and water pipes.  This is done with construction equipment such as backhoes and excavators. Unfortunately, trenching accidents can and do happen which can sometimes result in injuries and deaths.

As noted, trenching and excavation work is dangerous, due in part to the lack of compliance with OSHA construction standards.  Some reasons for lack of compliance with excavating standards include ignorance of the applicable rules, laziness in that complying with the standards takes significant effort, and a desire to reduce costs.  In some cases, lack of concern about worker safety may occur which enables various motives for employee negligence.

The primary hazard of trenching and excavation is an injury from collapse. Soil analysis is important in order to determine appropriate sloping, benching and shoring to prevent soil failure. Other hazards construction workers are exposed to include injuries from traffic crashes and construction machinery overturns; lifting mishaps; electrocution; heat stroke and tripping and falling, including into trenches. OSHA does a credible job of enforcement of trenching and excavation standards. Most injuries and deaths would be prevented by adhering to proper shoring and sloping safety standards.

Several issues to consider include:

Was the soil classified and was it done correctly?
Was the trench adequately sloped based on the classification?
Were ramps or ladders present to provide means of escape in the event of a cave-in?

Key quotes from OSHA:

Dangers of Trenching and Excavation

Cave-ins pose the greatest risk and are much more likely than other excavation-related accidents to result in worker fatalities. Other potential hazards include falls, falling loads, hazardous atmospheres, and incidents involving mobile equipment. One cubic yard of soil can weigh as much as a car. An unprotected trench is an early grave. Do not enter an unprotected trench.

Trench Safety Measures

Trenches five-feet (1.5 meters) deep or greater require a protective system unless the excavation is made entirely in stable rock. If less than five-feet deep, a competent person may determine that a protective system is not required. Trenches 20-feet (6.1 meters) deep or greater require that the protective system be designed by a registered professional engineer or be based on tabulated data prepared and/or approved by a registered professional engineer in accordance with 1926.652(b) and (c).

Competent Person

OSHA standards require that employers inspect trenches daily and as conditions change by a competent person before worker entry to ensure elimination of excavation hazards. A competent person is an individual who is capable of identifying existing and predictable hazards or working conditions that are hazardous, unsanitary, or dangerous to workers, soil types and protective systems required, and who is authorized to take prompt corrective measures to eliminate these hazards and conditions.

Access and Egress

OSHA standards require safe access and egress to all excavations, including ladders, steps, ramps, or other safe means of exit for employees working in trench excavations four-feet (1.22 meters) or deeper. These devices must be located within 25-feet (7.6 meters) of all workers.

General Trenching and Excavation Rules

• Keep heavy equipment away from trench edges

• Identify other sources that might affect trench stability

• Keep excavated soil (spoils) and other materials at least two-feet (0.6 meters) from trench edges

• Know where underground utilities are located before digging

• Test for atmospheric hazards such as low oxygen, hazardous fumes and toxic gases when > four- feet deep

• Inspect trenches at the start of each shift

• Inspect trenches following a rainstorm or other water intrusion

• Do not work under suspended or raised loads and materials

• Inspect trenches after any occurrence that could have changed conditions in the trench

• Ensure that personnel wear high visibility or other suitable clothing when exposed to vehicular traffic

Protective Systems

There are different types of protective systems:

-  Benching means a method of protecting workers from cave-ins by excavating the sides of and 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 other types of supports to prevent soil movement and cave-ins.

-  Shielding protects workers by using trench boxes or other types of supports to prevent soil cave-ins. Designing a protective system can be complex because you must consider many factors: soil classification, depth of cut, water content of soil, changes caused by weather or climate, surcharge loads (e.g., spoil, other materials to be used in the trench) and other operations in the vicinity.

 This article discusses issues of general interest and does not give any specific legal or business advice pertaining to any specific circumstances.  Before acting upon any of its information, you should obtain appropriate advice from a lawyer or other qualified professional.

This article may not be duplicated, altered, distributed, saved, incorporated into another document or website, or otherwise modified without the permission of TASA.
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