In July of 2008, an accident happened to a 35-year old contractor who was trying to connect a residential sewer line to the main sewage system. Unfortunately, the trench collapsed and left him trapped inside it. The victim was buried and covered with mud. In response to this accident, the Hamilton County Technical Rescue Team and the Fire Department from Fishers, Carmel and Westfield, Indiana responded to liberate the trapped contractor from the trench cave-in.

To remove mud, water and dirt from the trench, vacuum trucks were needed. Three such vehicles arrived on the site. The first truck was primarily for extracting mud; the second was to continue the application if the first one became filled; and the third was in case a mechanical breakdown occurred with the first and second ones. A 100-foot hose was attached to the truck, which went down to suck the mud, water and soil out. With the coordination of the various rescue teams, and through the use of this valuable vehicle, they were able to save the victim who was on the verge of death.

Emergency Role

In any trench recovery, the role of vacuum trucks is very important. Rescue teams of the various fire departments are always ready to respond to emergency cases such as trench retrieval. Statistics show that the fatality rate of this kind of incident is 65 percent, which means that trenches are very life-threatening spots for both the contractors and rescuers.

These vehicles can be used to accelerate the removal of soil. This speeds up the process of soil removal by 80 percent. Most cities in the United States have one or more of these valuable vehicles ready to be used to help save an individual trapped in a collapsed trench.

This kind of truck has several categories based on the manufacturer, capacity and number of axles. There are vehicles that suck up either solid or liquid materials, or both, with a low-velocity to a high-velocity capability to handle both solid and liquid materials.

Various Types

There are two types of vacuum trucks; one that uses a centrifugal fan unit and one that uses a Positive-Displacement Air Pump. The first type functions similarly to a home vacuum cleaner and the fan creates airflow of 3,000 to 8,000 cubic feet per minute which helps in the effective extraction performance. The second type can generate airflow of 2,000 to 3,000 cubic feet per minute. The vacuum pressure on a fan unit is measured in water (H20) while the pressure on the air pump is measured by mercury (Hg), which is why the Positive-Displacement Air Pump has higher vacuum pressure.

These versatile trucks are effective machines to perform trench rescues; however, there are still hazards that may or may not occur during the recovery operation. The identified hazards include: the weight of the vehicle in proximity to the rescue (distance should be 15 feet away from the trench); the vibrations generated by the machine (a 300 feet vibration-free zone should be established); and the capacity of the vacuum to suction anything in its airflow path (high-pressured airflow can injure both the victim and the rescuer).

Extraction is another forward-looking way of saving someone partially or totally covered in trench cave-ins. It is important that all possible safety considerations be taken into account before using the vacuum truck, especially when dealing with the safety of both the rescuer and the victim. Then this powerful extraction machine on a truck can be used to save the day!