ALTHOUGH CALLS TO TRENCH/excavation accidents are not that frequent, fire departments should be prepared to respond to such incidents. The clipboard drill below focuses on some basic operational considerations for the first-arriving companies regarding awareness, operations, and technician level training.
The National Institute for Occupational Safety and Health (NIOSH) reports generally indicate that, annually, there are approximately 1,000 work-related injuries and approximately 70 to 75 worker deaths resulting from excavation cave-ins or trench accidents.
A trench is an excavation that is deeper than it is wide. An excavation is defined as an opening dug in the ground. Responders should consider the following facts concerning the dirt. One cubic yard of dirt weighs about 2,700 pounds; one gallon of dirt weighs approximately 13 pounds. One cubic yard of dirt would fill about 230 one-gallon buckets, and one cubic foot of dirt would fill about eight one-gallon buckets. Translating that to the load bearing on buried victims, this weight can cause mechanical asphyxiation, crush syndrome, suffocation (from the packing of a victim’s mouth and nose with soil), and other life-threatening conditions.
Standards. The Occupational Safety and Health Administration (OSHA) has adopted several standards concerning trench operations. OSHA Standards 1926.650 through 1926.652 concern requirements for excavation, protective systems, and timber and aluminum shoring requirements. Most state fire academies recognize three separate trench rescue operation training levels: awareness, operations, and technician.
National Fire Protection Association (NFPA) 1670, Standard on Operations and Training for Technical Rescue Incidents (2004 ed.), identifies the minimum requirements for trench rescue awareness, operations, and technician level training. Awareness level training involves recognition of the trench rescue situation (soil type and hazards, trench collapse patterns), setting up site control, and initiating rapid nonentry extrication of minimally injured victims.
Operations-level training involves conducting safe operations at individual nonintersecting trenches of less than eight feet deep with no severe environmental conditions, including size-up, soil identification, recognition of unstable areas, identifying possible victim locations, initiating entry, setting up shielding systems, and victim extrication.
Technician-level training involves operations at individual or intersecting trenches deeper than eight feet, with possible severe environmental conditions; deployment of manufactured trench boxes or isolation systems; and monitoring the trench atmosphere for oxygen content, flammability, and toxicity.
Conditions. Responding firefighters must ask: How did the accident happen? This may affect the operational rescue plan. Several conditions present at a trench/excavation collapse may include the following:
- disturbed soil,
- intersecting trenches,
- narrow right-of-way,
- vibrations,
- increased seepage of subsurface water,
- dried-out exposed trench walls, and
- inclined layers of soil sifting into the trench.
Most trench/excavation accidents occur at sites that are between six and eight feet deep and about six feet wide.
Soil is classified as compact, saturated, or running. Compact soil is considered somewhat stable. In saturated soil, you can actually see water seeping through. Running soil is loose and free-flowing, almost like a sugar sand.
Beware of clay-type soil! In a review of 82 cases of wall failure, 32 involved walls made of clay-type soil. Most training courses will point out that although clay-type soil looks strong, its appearance is very deceptive; hence, it is very dangerous.
Trench/excavation accidents generally result from the cave-in of the lip (corner edge) of one or both sides of the trench, slough-in (crumbling) of one or both trench walls, or shear-away and collapse of one or both trench walls.
Tools and equipment. Most technical rescue teams across the United States are well equipped for a trench/excavation incident. Listed below is basic equipment that may be needed at a trench/excavation accident:
- plywood sheeting/planking and pallets,
- single planks (about 2 × 12 × 12 inches),
- portable trench panels (about 1 1/8 inches thick recommended),
- uprights (2- × 10- × 10-inch planks),
- Shoring material (lumber four inches thick and between 10 and 16 feet long to be cut to size on-site),
- screw-type trench jacks,
- hydraulic shoring or struts, and
- pneumatic shoring.
This is a general list of equipment that may be needed. Each department or technical rescue team should have the equipment that addresses its specific needs and have personnel properly trained in trench/excavation operations.
Additional equipment includes adequate lighting, portable ladders, hand tools, dewatering equipment such as portable pumps, and high-angle rope equipment. As you can see from the above list, a trench incident can turn into a lengthy technical operation involving many agencies.
Vacuum trucks have been used effectively to remove dirt in trench operations and may be available from utility companies. All responders should strongly consider dispatching this piece of equipment on receiving a report of a trench incident in their district. The Fire Department of New York (FDNY), the Los Angeles County (CA) Fire Department (LACoFD), and other departments request at least one vacuum truck for all working trench rescues; some request three units (one for primary operations, the second to continue vacuuming when the first one is full and needs to dump its load, and the third as a backup in case of mechanical breakdown of the first two).
FDNY, LACoFD, and other departments are also using a new device called a rescue vacuum that attaches to the vacuum truck’s hoses and has specially designed hard extension tubes and wands that allow rescuers to reach down deep into a trench collapse to remove entrapping dirt from around victims before shoring is completed and during operations in trench collapses with emergency shoring in place. The rescue vacuum’s utility has been demonstrated in training and in actual incidents to cut dramatically the time to free the victim.
Initial operations and size-up. In trenches more than four feet deep, place portable ladders at different points for access, and shore the sides to protect the team working inside the trench. Keep arriving units at least 100 feet from the trench, and limit vibration in the immediate area of the trench.
Size-up report points for the incident commander include the following:
- What happened? Is it a cave-in, or is the victim just entrapped?
- Number of victims and their locations?
- Type of injuries?
- Is this a rescue or recovery operation?
- Any site hazards?
- Are sufficient staff/technical equipment available?
Some technical rescue teams use the following 10-step plan for response to a trench/excavation incident:
- preparation: training/equipment,
- response plan,
- assessment,
- hazard control,
- support operations,
- gaining access,
- disentanglement,
- packaging,
- removal, and
- termination.
Remember, a trench operation is a tremendous team effort-no one person completes such an operation alone. These are just some very basic items to consider when called on to respond to an accident involving a trench/excavation. Although trench/excavation incidents are not the most common responses of fire departments, having a game plan in place before one happens will certainly help ensure a successful resolution.
TOM DONNELLY is a member of the Fire Department of New York, where he serves as a lieutenant assigned to Rescue Company 1. He previously was a firefighter with Ladder Company 176 and Rescue 2. He is an instructor in the FDNY Technical Rescue School and has been an instructor with the Suffolk County (NY) Fire Academy for 15 years. He has been a volunteer firefighter with the Deer Park (NY) Volunteer Fire Department for 23 years. He has a B.S. degree in human resource management from St. Joseph’s College, Brooklyn, New York, and has been an FDIC instructor for several years.
