Emergency response and trench rescue

Everything in the previous lessons is aimed at making sure this lesson is never needed. But collapses, gas strikes, medical emergencies and injuries still happen, and the first few minutes decide how many people go home. The instinct to jump into a collapsed trench and dig out a co-worker by hand is powerful and understandable. It is also one of the main reasons trench collapses kill more than one person. This lesson covers planning for emergencies, what to do in the first minutes, how technical rescue works, and the reporting and investigation that follow.

Why untrained rescue kills

A trench that has collapsed once is likely to collapse again. The first failure removes the soil that was supporting the remaining walls, and the walls above and beside the slide are now steeper and more stressed than before. Spoil, workers and equipment rushing to the edge add load just where it does the most harm. Secondary collapses commonly occur within minutes of the first.

A buried worker cannot simply be pulled out. Soil packs around the body and grips it; pulling on arms can dislocate joints without freeing the victim. Soil pressing on the chest prevents breathing. Rescuers digging with shovels risk striking the victim, and an excavator digging near a buried person is likely to injure or kill them.

Planning before the work starts

Ontario's O. Reg. 213/91 requires the constructor to establish written emergency procedures for the project, and every employer must plan for the emergencies its work could cause. For excavation work, the emergency plan should answer specific questions before the first bucket of soil is removed:

• Who calls for help, how, and what will they say? Cell coverage, the site's address and access route, and the nearest cross street should be written down.
• Does the local fire service have a trench rescue team, and how long will it take to arrive? Rural areas may wait an hour or more for a technical rescue team from a larger centre.
• What first aid supplies, trained first aiders and equipment are on site, and where?
• How will the gas, electrical and water utilities be contacted to isolate their facilities?
• Who will meet the emergency services at the road and guide them in?
• How will equipment and traffic near the trench be stopped?
• What rescue equipment is on site for hazardous atmosphere incidents, such as a retrieval line and harness for a worker in a trench, where entry rescue is not needed?

The plan should be reviewed with the crew at the start of the job and at tailgate meetings, so everyone knows their role without having to think about it.

The first minutes after a collapse

When a trench collapses with someone inside, the first actions are:

• Call 911 immediately. Say clearly that there has been a trench collapse with a worker buried, so that dispatch sends a technical rescue team as well as paramedics. Give the address, access route and the number of people trapped.
• Keep everyone out of the trench and back from the edge. Do not let co-workers enter to dig. This is the hardest instruction to enforce, and the most important.
• Shut down equipment near the trench and stop traffic, compactors and any other source of vibration, but do not move the excavator if moving it could load the edge or the victim.
• Do not remove spoil from around the edge or try to dig the victim out with a machine.
• If a worker trapped only partially and fully conscious can be helped out safely from within a protected area, for example inside an intact trench box, that may be done; otherwise wait for trained rescuers.
• Keep track of where the victim was last seen, and whether anyone else might be missing. Count heads.
• Call the utilities if any facility has been damaged, and keep ignition sources away from any gas.
• Send someone to the road to meet and guide the emergency services.
• Gather information for the incident commander: depth and dimensions of the trench, soil type, time of collapse, the victim's position, utilities in the area, and any hazards such as gas or water.

How technical rescue works

Fire services that provide trench rescue train their technical rescuers to recognized standards, such as NFPA 1006 for rescuer qualifications and NFPA 2500 for the operational capability of rescue teams. A trench rescue typically follows a sequence: size up the scene, control hazards such as utilities and traffic, stabilize the lip of the trench with ground pads or plywood to spread the weight of rescuers, install panels and struts to shore the walls around the victim, and only then enter to uncover the victim, often by hand and with small tools. Air may be supplied to the victim while this happens. The process can take hours. Rescuers will not enter until the walls are shored, because they know that an unshored trench is likely to collapse again.

The crew's job is to make that process faster and safer: clear access for the rescue vehicles, a clear briefing, equipment stopped, utilities isolated, and nobody adding to the problem. Contractors can also offer resources the fire service may lack, such as trench boxes, plywood, timber or a vacuum truck, under the direction of the incident commander.

Other emergencies in excavations

• Gas strike: follow lesson 4. Evacuate upwind, eliminate ignition sources and call 911 and the gas utility. Account for everyone, including workers who were in the trench.
• Hazardous atmosphere: if a worker collapses in a trench, assume the air may be the cause. Do not enter without testing and appropriate respiratory protection. Use a retrieval line if one is attached. Ventilate and call for help.
• Flooding: get workers out by the nearest ladder immediately; do not wait to save tools or equipment.
• Electrical contact: keep everyone away from the machine and any energized ground, call the utility, and do not touch a victim who may still be in contact with the source.
• Medical emergencies: a worker who has a heart attack, heat stroke or injury in a trench still needs to be brought out safely. Plan how a stretcher could be lifted out, and remember that the trench must still be protected for responders.

First aid for trench victims

Trench victims may have crush injuries, suffocation, spinal injuries, fractures, hypothermia and shock. First aiders should follow their training and the instructions of the 911 dispatcher until paramedics arrive. Crush syndrome is a particular concern: when pressure on a large muscle mass is released after a long time, toxins and potassium released from damaged muscle can cause heart rhythm problems and kidney failure. That is why technical rescuers and paramedics coordinate the moment of release, and why victims who seem fine after being freed still need hospital assessment.

Reporting and investigation

After a fatality or critical injury in Ontario, the employer and constructor must notify the Ministry of Labour, Immigration, Training and Skills Development, the joint health and safety committee or health and safety representative, and the union, if any, immediately by telephone or other direct means, and provide a written report within 48 hours under section 51 of the OHSA. The scene must not be disturbed except to save life, relieve suffering, maintain an essential public utility or prevent unnecessary damage, until an inspector gives permission. Other provinces have similar requirements. Damage to buried facilities must be reported to the owner, and the regional one-call or damage prevention body collects reports to identify trends.

An investigation should look past the immediate cause, such as no trench box, to the reasons behind it: was a box on site, was the competent person present, was the schedule realistic, did the crew feel able to refuse, and had similar shortcuts happened before without consequence? Fixing those underlying causes prevents the next incident; blaming the victim does not.

Supporting the crew afterwards matters as well. Workers who witness a collapse or a co-worker's death can suffer serious psychological effects; employers should arrange access to critical incident support and employee assistance programs and should not pressure the crew to return to the trench immediately.