Excavation, Trenching, and Shoring Safety: Preventing Collapses & Ensuring Worker Protection

There's several reasons the trench might collapse, including water absorption into the soil, the type of soil being excavated, vibrations in the area and weather. We all know water is vital to life, but it can mean death in regards to trenching and excavating. When water is absorbed into the soil, it undermines the structural integrity of the size of the trench and makes it harder for workers to climb out if needed. The Occupational Safety and Health Administration, or osha prohibits workers from getting into a trench site that has accumulated water in it. Any water should be removed with a water removal system overseen by a competent person and the trench given suitable time to reach safe working conditions. Or workers should be attached to a safety harness and lifeline. If the trenching interferes with a natural drainage area, OSHA requires the use of diversion ditches to keep the water from entering the site. Vibrations in the area can also disrupt the trench or spoil pile, causing a collapse. Vibrations can come from natural phenomena like nearby storms, traffic near the area, or even the equipment being used on the construction site. Weather can also cause dangerous conditions for trenching. Just as overly moist soil is hazardous, so are hot and dry conditions. Soil that's too loose can crumble easily, causing unsafe conditions and could possibly lead to a collapse. Rainy and wet weather can lead to water accumulation and soft walls. OSHA allows the use of shield systems in order to maintain a dry trench in wet conditions. All soil must be inspected carefully before any excavation work begins. OSHA identifies three types of A, B and C. We'll dig a little deeper into each type of soil in a bit. For now, it's important to note that in the case of a collapse and rescue mission, all soil should be considered type C, the least stable. Trenching Accidents kill at least 40 workers a year and deaths or serious injury can occur within minutes of a cave in. This is why having a good emergency management system in place is key. The first step is to establish command. The command area must be at least 150ft from the trench and any machinery used in the rescue should be a minimum 50ft away from the collapse. Once command is established, the jobs that should be assigned include rescue sector, safety officer and technical advisor. Each job has its own responsibilities. For example, the rescue sector assumes all technical rescue operations, developing the plan and communicating during all aspects of the rescue. The safety officer and technical advisors are responsible for the safety and well being of the victims and rescuers during the process and ensure that the rescue plan is sound. The next step is for a member of the rescue party to perform a size up. This is when information regarding the incident is gathered through questioning and observation. Important information includes the location and number of victims in the collapse. Rescuers need to know how far down the victims are, how many there are and the possibility of injuries. This is also the step where the scene is secured and additional resources are called for if needed before moving forward. The next step is to determine if this is a rescue or recovery mission. During the size up process, the amount of time since the collapse and the condition of the victims will be determined. All local traffic should be rerouted at least 300ft from the trench and all heavy equipment operating on the site should be stopped. Non essential personnel should be kept at least 150ft away. Before rescuers enter the cave in an inspection of the area needs to be completed. This would include looking for any other hazards including fissures, tripping hazards near the trench and an unstable spoil pile. It's recommended that a ground pad, most commonly plywood, is used to distribute the weight of the rescue team. Once the rescue team is ready to enter the trench, they need to follow certain safety measures. Two ladders no more than 50ft apart should be placed inside the trench for entering and exiting. A shoring system needs to be chosen and used on the non collapsed area. Types of shoring systems will be discussed in the next section. Dirt from the collapse zone should be removed safely and any obstruction like pipes, must be secured. In incidents that don't involve a cave in, the item trapping the victim needs to be carefully removed, their condition assessed and the victim removed from the trench. If a collapse has occurred, dirt removal should begin from a safe zone. Use small shovels, buckets or hands when removing dirt off a victim beginning at the diaphragm. Once uncovered, assess the victim and remove them carefully from the trench. Any life threatening injuries should be assessed immediately and the victim transported to the hospital for further treatment. After the rescue is complete, ensure all rescuers and other personnel are accounted for. All tools and equipment must be removed from the trench. Using a last in and first out system, rescuers should reconvene for a post incident debrief and the scene turned back over to the employer. While having a rescue protocol in place is important, it's always best to prevent incidents before they occur. Following pre entry safety measures, it.