Safety in Trenches or Excavations: Eliminating Hazards and Responding to Emergencies
Excavations or trenches are one of the biggest culprits for injuries and fatalities in the construction industry. In fact, according to the Occupational Health and Safety Administration (OSHA), excavations cause more accidents than general construction operations. The fatality rate for excavation is about 112% higher than that for general construction.
A few months ago, we featured an article about the Top 10 OSHA Fines for Small Companies. On that hot list, the category Specific Excavation Requirements came in as having the second biggest total amount of fines. In 2007, it produced 1,362 citations, amounting to more than $1.6 million total of fines. That’s an average of $2,110 penalty for every small company cited last year for this category.
Cave-ins, asphyxiation, explosion and electrocution are just some of the hazards posed by trenches or excavations. The challenge is in performing active measures to control or eliminate these trenching hazards. Employees can do this by equipping themselves with proper training, personal protective equipment (PPE) and emergency equipment.
Controlling/Eliminating Common Excavation Hazards
OSHA requires that employers have a competent person inspect a trench or excavation every day, before starting each shift. A competent person assigned to inspect trenches must:
- Be knowledgeable of the OSHA requirements
- Have training in soil analysis
- Have authority to immediately eliminate hazards.
- Have training in the use of protective systems
During inspection, the competent person must control or eliminate any hazards that may be present in the excavation. Inspections must also be done every time changes are made in the condition of the trench. This includes rain and other “hazard-increasing events”.
Here are conditions and factors usually present in or near excavations, the hazards they pose and ways to eliminate or control these hazards:
- Utility lines or pipes
Before opening an excavation, contact utilities (gas, electric water, telephone, sewer) first to find out the exact locations of underground lines. Hazards posed by utility lines range from drowning to electrocution. If the excavation work happens to be near utility lines, you must use non-conductive tools.
- Inadequate ventilation or presence of hazardous gases/fumes
Asphyxiation is one common cause of fatalities in trenches. This is often a result of low oxygen and/or presence of hazardous fumes or toxic gases in the trench.
Before entering an excavation, the competent person must test for low oxygen, toxic gases, and hazardous fumes. Make sure to provide enough ventilation and respiratory protection appropriate to the condition of the excavation.
Photo by Kevin Connors
- Vehicular traffic
If the trench is exposed to public vehicular traffic, workers must be provided with highly visible PPE like orange warning vests. They may also don PPE made of reflectorized material.
- Vehicles and other mobile equipment
Some excavations have trucks and other mobile equipment operating adjacent to them or by their edges. In such cases, you must set up warning systems like barricades, stop logs and/or hand or mechanical signals.
- Falling loads
Employees working in trenches may also be in danger of being hit or trapped by falling loads from forklifts and other equipment. For this reason, they should be required to stand a safe distance from any vehicle being loaded or unloaded.
Unsafe Access and Egress
Besides cave-ins, falls are a major result of excavations not having the right kind of entry (access) and exit (egress). Trenches with a depth of 4 feet or more must be provided with ramps, ladders, or stairways as means of access and egress. Such structures must be designed by a competent person.
An egress must be positioned within 25 lateral feet of workers. When there are two or more components forming a runway or ramp, they must be connected to prevent displacement. They must also be of uniform thickness.
Sometimes, excavated material or “spoils” are too close to the edge of a trench. This poses a cave-in hazard to employees working in the trench.
In such cases, you must set spoils and equipment at least 2 feet back from the trench. If this is not feasible, you have to haul spoils to another location.
If spoils can remain near the trench with a two-foot allowance, retaining devices, like a trench box, must be used to prevent spoils and equipment from falling into the excavation.
Emergency Rescue Equipment
Employees must always have emergency rescue equipment, whether or not hazardous atmospheric conditions exist or are expected. Examples of rescue equipment are breathing apparatus, safety harness and line or a basket stretcher.
When employees have to enter bell-bottom pier holes, or similar trenches, they must don a harness with an attached lifeline. This lifeline must not be attached to other lines used to handle materials.