Trench rescue is a very dynamic event. Soil conditions and situational activities will have a direct influence on how the rescue response is carried out.
As one of the top low-frequency, high-hazard responses we are called to, our situational awareness must be at its highest level.
The actual trenches we will be called to have already experienced one or more uncontrolled movement of earth. Safety is paramount; this includes the safety of workers on the scene and other Good Samaritans who were on scene prior to your arrival.
Let’s starting with training. Many improper habits are formed during our initial exposure to a trench operation.
One of our first priorities on scene is scene security and control. However, during training we circumvent this by having the students surround the trench area so they may observe and learn.
The problem now lands on the actual incident where many of the responders, technically trained or not, end up in a similar position – that of surrounding the trench to “get a look” at what is going on.
Often our best actions are those we take upon arrival during on-scene assessment. Make it a formal part of your response procedures to create a secure zone near and around the trench to protect the victims as well as those responding to the incident.
A trench incident varies in scene lay out from the traditional practice of drawing three circles (cold, warm and hot zones) and calling it good.
Specialized equipment
We use a vacuum system to support our trench operations as do may other agencies around the country. With this specialized tool in play, we must also consider the need to establish and maintain an open travel lane for the vac-truck.
Not only must they have access to the scene, we have to keep a clear path for them to exit. The vac-truck’s capacity is large, but not always large enough to complete the mission in a single load.
Much like a water-shuttle operation, the truck must be able to exit the scene to dump and return, or to exit and be replaced by an addition truck that is staged near the incident.
The vac-trucks are similar in size to many aerial apparatus. Maneuverability is not always easy, especially when the incident is off the paved or hardened surfaces.
These trucks are also very heavy; we must take extra precautions to not negatively impact the trench by placing this vehicle to close to it. Positioning may have to be delayed until the trench is shored.
When using these types of specialty tools make sure you are properly trained in its capabilities and limitations. Having a vacuum safety relief valve is imperative. These trucks are capable of sucking large rocks and other significantly sized items with no problem.
Use ultimate caution when working around any victim. It is highly recommended that you do not use the standard hoses from a vac-truck to work around a victim without the additions of a specially designed accessory that contains the needed safety features.
Trench configurations
Once again, the methods used during training for a trench response may leave us not fully prepared for the conditions we will encounter. I have never run into an active trench at an incident that has nice 90-degree walls and bottoms.
Simulators and site-dug training trenches all too often fall into that category of having nice defined walls and edges.
Practice and prepare for extremely uneven and awkward trench configurations. As a rule of thumb, try to consider all trench situations as containing Type C soil.
Characteristics of Type C soil include:
- Cohesive soil with an unconfined compressive strength less than half a ton per square foot.
- Granular soil including gravel, sand and Loamy sand.
- Submerged soil or soil from which water is freely seeping.
- Submerged rock that is unstable.
- Material in a sloped, layered system where the layers dip into the excavation or a slope of four horizontal to one vertical or steeper.
When working with soil and in a trench environment, remember, you will not out run it. Shear wall collapse happens at approximately 45 mph. Also, you are not going to lift it off you; 18 inches of soil on a body weighs between 1,000 and 3,000 pounds.
For more information on soil types, review OSHA Standard 1926.650 along with the related sections and subparts associated with excavations and trench operations.
Victim considerations
Victims in a trench exhibit both visual and not-visual injuries, which makes their initial care and handling even more important. Crush injury syndrome is very common at a trench collapse.
The weight of the soil can compress the victim’s chest cavity to a point where they can no longer take a breath. The significance of getting this pressure off the victim and providing the needed medical care is imperative to their long-term survival.
This is why we must practice rapid victim access and have the tools and materials available as soon as possible to begin patient care and removal.
In most training cases, a mannequin or some object is placed in the trench to represent the victim. Not having the opportunity to train with live victims leaves a gap in our learning curve.
To help fill this gap and prepare your people for these challenges, I recommend bringing in medical providers who can present information on the treatment of patients with crush injury syndrome. Knowing what not to do is as important as knowing what to do when it comes to patient care.
For more information on crush syndrome, check out “4 things EMS providers must know about crush syndrome”.
Trench responses can challenge even the best-prepared organizations. Always remember, the more we know about these challenges, the better our members will perform at these calls.
