TACTICAL CONSIDERATIONS FOR EXCAVATION COLLAPSE EMERGENCIES
BY ROBERT RHEA
Public safety personnel responsible for mitigating trench collapse entrapments will face a challenging test. Rescuers accustomed to taking quick action and mitigating rescue situations in short order will quickly realize that trench collapse entrapments often become long-term operations. Effective management of a trench collapse incident requires accurate analysis of the incident, strong scene-control techniques, proper hazard-control applications, and effectual support operations.
Excavation collapse situations can occur while constructing new underground utilities, repairing existing underground utilities, repairing building foundations, or engaging in other belowgrade construction work. Victims can be trapped by collapsed trench walls, sliding spoil piles, dislodged utilities, failed shoring, or heavy equipment and other materials that fall into the trench. To determine the exact problem, rescuers must adequately analyze the situation.
ANALYSIS
During the analysis phase, gather information from various sources. Start with dispatch. Determine from the dispatcher the exact location of the event. Is it at a construction site? What is the best route to the site? Can large rescue vehicles access the area of the construction site where the collapse has occurred? Do you need to consider calling for four-wheel-drive vehicles to carry your equipment to the collapse site? Can you use on-site construction trucks or heavy equipment to carry your equipment through a muddy field to the site?
Try to determine from the dispatcher whether the victim is partially or fully buried. Are utilities involved? If so, get the utility company to respond as soon as possible. How many victims are involved? What level of EMS service is currently responding to the event, BLS (basic life support) or ALS (advanced life support)? Collapse situations will require advanced life support resources.
Note: Develop dispatcher training and protocols so that emergency communications call-takers ask the appropriate questions to determine that a belowgrade emergency exists and that appropriate resources are dispatched to the incident. The resources that will be dispatched will depend on local standard operating procedures and should include rescue teams trained in trench rescue operations.
As you arrive on the scene, stop the apparatus short of the actual trench collapse site and walk in to the site. Observe the surroundings before the victim`s coworkers or bystanders converge on you, demanding immediate action. Observe the area for victims outside the trench, potential crowd-control problems, actions currently being taken by others in an attempt to rescue the trapped patient, and site hazards.
As you approach the trench, make sure you do not cross over the spoil pile or walk up to the edge of the trench to view the collapse area, or you may cause a secondary collapse. To see the collapse site and victim location(s), view the incident from the narrow end of the trench. This end is the more stable area for approach.
Gather additional information from the job foreman, other construction workers, and other witnesses. At this time, determine the following:
Entrapment conditions–partial or total burial, entrapment by other mechanisms.
Disrupted utilities.
Patient accountability–total number inside and outside the trench.
Hazards in need of control.
Resources needed to mitigate the event. They include properly trained personnel, adequate shoring materials, extrication equipment, and support materials.
SCENE CONTROL
After analyzing the incident and requesting or ensuring that adequate resources are assigned to the incident, strong scene-control measures must be implemented. These measures must include control of the site to limit access to the work area by construction workers, bystanders, or unnecessary response personnel. Physical barriers to identify control zones and access corridors into the work area must be erected. Fire line tape, traffic cones, or other marking devices may be used for these barriers. Summon the police department to assist with crowd and traffic control.
Apparatus staging is required to control road access to the site and limit the amount of equipment placed near the collapse site. All apparatus should be at least 100 feet away from the trench to eliminate the potential for superimposed loads, vibrations from engines, and engine exhaust from impacting the environment around the trench.
Establishing tool and equipment work stations close to the trench will facilitate timely retrieval of materials.
Initial nonentry patient care can be given during the scene-control phase. If the patient is partially buried and conscious, a helmet and an oxygen mask (supplied from outside the trench) can be lowered to the patient. Someone should be assigned to communicate with and reassure the patient and explain what is being planned. If the patient is partially trapped and does not appear to be badly injured, you can lower a shovel to him to encourage him to begin self-rescue digging operations. He likely would be in the best position to dig around himself.
During the scene-control phase, command positions are established within the rescue team. Functional positions requiring management include logistics, personnel, safety, and rescue operations. The incident commander (IC) should brief all rescue team members to ensure that all clearly understand the rescue plan. The briefing should include a review of the command position assignments, the primary and secondary rescue plan, the order of events, and the shoring plan. This meeting will be enhanced if a diagram of the trench and shoring installation plan can be drawn on a small chalkboard or erasable marker board.
HAZARD CONTROL
After the scene has been brought under control, rescuers must focus on managing scene hazards.
Note: Hazards must be identified and controlled as outlined in OSHA Excavation Standard 1926.650 and 1926.651. Ground-level hazards include vibration sources, superimposed loads on the edge of the trench, and spoil pile instability. All contribute to potential secondary collapse.
Environmental hazards include hazardous atmospheric conditions in and around the trench or excavation. These conditions may be the result of a natural decay process, leaking utility lines, or chemical spillage. Atmospheric monitors must be used to ensure that an acceptable atmosphere exists in and around the trench throughout the event. Ventilation fans should be used in conjunction with atmospheric monitors to ensure safe working conditions for rescuers.
Assess the underground and aboveground sites to determine if they are damaged, leaking, or in danger of being disrupted. Support exposed utilities within the trench to limit the potential for breakage. Aboveground utility poles next to a trench or fire hydrants next to an open trench may need to be supported by installing shoring next to the location to limit the potential for undermining.
Control groundwater in the trench and rainwater runoff entering the trench to limit the destabilization of trench walls. Trash or dewatering pumps and diversion dikes can be used for this purpose.
Shoring trench walls is a primary hazard control task. No one should enter the trench or excavation until safe zones have been established through the installation of qualified shoring systems. The shoring plan developed by rescue personnel should be based on soil conditions, the type of collapse, the depth of the trench, the effect of groundwater or rain on the stability of the trench wall, and the shoring materials available.
Note: Shoring materials and the design of the shoring system must meet the requirements of OSHA Excavation Standard 1926.652, Requirements for protective systems. Follow system-related tabulated data or manufacturers` specifications for materials and shoring equipment.
The initial shoring system should be installed in the area close to the victim to provide an area of protection as quickly as possible. The shored area should then be expanded out away from the patient, to allow a wider area of protection for rescuer access. Always install the shoring system from an area of safety, either outside the trench or from an area already shored and stabilized.
Rescuers must also assess the impact of the trench collapse on the stability of any undermined street pavement, sidewalks, curb and gutter, or buildings. If any of these are found to be unstable, rescuers will have to reassess the ability to safely work inside the trench. Structural engineers or building inspectors should be consulted to determine the hazards to rescuers. Additional shoring systems may be needed to stabilize undermined buildings, sidewalks, or other structures.
EXTRICATION
After an effective shoring system has been installed and continued hazard control is in place, procedures for extricating the victim can be implemented. Many hours of controlled digging operations will be needed to free a victim pinned by large amounts of soil. Move the soil away from the victim`s face, head, and chest as soon as possible. Introduce BLS care as soon as the victim can be safely reached.
Soil type and water content will affect the degree of difficulty in removing the soil. Small entrenching shovels or hand trowels can be used in areas close to the victim`s body. These smaller digging tools limit potential injury to the patient and make it easier for rescuers to work within the limited work area. Air-powered vacuum devices can also be used to remove soil. The dirt can be relocated to an area of the trench where it has been confirmed that no other victims are or removed from the trench by small buckets attached to ropes.
Digging bars or air chisels may be needed to break apart hard compact soil or rock. As rescuers remove large amounts of soil, they must constantly reassess the adequacy of the shoring system. As additional soil is removed, the trench wall area below the existing shoring will become exposed. Additional supplemental shoring will be required as this occurs. Assessment of the stability of the trench wall must be ongoing, and shoring materials must be designed and installed to counteract any instability.
Resist the tendency to want to pull the victim out of the entrapping soil before he is fully uncovered. The weight of the soil and associated suction will not allow this to work. The patient must be fully uncovered to be properly packaged for removal.
Trench collapse victims may also be trapped by tools, ladders, or other equipment that was in the trench at the time of the collapse. The weight and force of the collapsing soil may cause the victim to become pinned or impaled by these tools. Be prepared to use power tools to cut through shovels, ladders, or other materials that may pin the victim during the collapse.
Victims of a trench collapse may also become pinned under large concrete pipes that fall into the trench or boulders that have slid out of a trench wall. Air bags or other lifting equipment is needed for these types of rescues. As lifting operations in the trench progress, constantly evaluate their impact on the existing shoring system to ensure that the system does not become compromised. Also, if the lifted object should contact a shoring member, the installed system could collapse.
Alternative lifting operations may include the use of block and tackle systems, chain hoists, and other rigging materials in conjunction with an overhead anchor for support. If heavy equipment is to be positioned near the trench for lifting operations, consider the effect of adding these superimposed loads to the trench area. The load can be offset by reinforcing the existing shoring system with additional materials to compensate for the added surcharge load on the trench walls.
PATIENT PACKAGE AND REMOVAL
As access to the victim is established and entrapment materials are removed, the patient can be packaged and prepared for removal from the trench. Patient care and packaging decisions must be based on the patient`s position and the types of injury associated with a violent collapse. Spinal column injuries, impalements, and crush syndrome are all potential injury patterns to consider.
Note: Patient treatment considerations include airway management, spinal immobilization, crush syndrome management, and other trauma-related injury treatment.
As soil or other entrapment materials are removed to make room for patient packaging, ensure that adequate shoring systems are in place to allow for properly placing the patient into the removal device. The shored area should be large enough (a 10- to 12-foot horizontal area) to allow the patient to be placed into the transfer device without rescuers or the patient being exposed to an unshored trench. This may typically occur when a the patient is found lying down and needs to be moved horizontally into a litter for removal from the trench.
Several options may be used for removing the victim from the trench. Stokes baskets may be used, although they may be difficult to maneuver around shoring systems. A flexible SKED stretcher with a spine board normally is better suited for this situation, since it has a narrow profile and is flexible. Both devices will require rope-rigging equipment to raise the patient and the transport device out of the hole.
Options for rigging and lifting the patient include any variety of rope-hauling systems attached to ladder A-frames, ladder gins, aerial ladders, or heavy construction equipment. Use heavy equipment and aerial devices only as overhead anchors, not as powered mechanical lifting devices.
A “low-tech,” safe, and effective method for removing a packaged patient is to use a ground ladder as a ladder slide or to slide the packaging device up a ground ladder that is being supported and guided by rescuers.
The entire packaging and removal operation must be planned during the early stages of the operation. It takes time to analyze the situation, develop a plan, gather equipment, and set up rigging systems. So it is imperative that early planning and coordination take place to ensure a smooth transition from the extrication phase into the patient-removal phase.
Additionally, since a large majority of trench collapses occur at construction sites, it is important to assess rescuers` ability to quickly move the patient to a transport vehicle once he has been removed from the trench. This task may not be as simple as walking the patient to an awaiting ambulance. Quick transport may be hampered by muddy grounds, uneven terrain, construction materials, tripping hazards, and the long distance to the transport vehicle. Again, early analysis and planning for this potential problem will help to minimize delays in patient transports.
SUPPORT CONSIDERATIONS
Effectively commanding and controlling trench collapse incidents depend on the IC`s ability to recognize the need for adequate support functions that will surface at various times during the event. These functions will vary with the complexity of the collapse and entrapment.
Staffing support requirements need to be forecast and properly managed. Personnel are needed to rotate rescuers out of the trench and into rehab during difficult and lengthy extrications. Adequate staffing must be assigned to the equipment or logistics area to help with the movement of tools and equipment, cutting of shoring materials, and the placement of lighting and ventilation equipment. Staffing may be needed to set up water diversion or pumping equipment to handle water runoff into the trench during inclement weather.
Long-term operations will require additional staffing to assist with command post operations and rest and rehab for command personnel. Rehabilitation for the rescue team is a primary concern and must be properly coordinated. Long-term digging operations will necessitate that rescue personnel rotate in and out of the trench. The IC must ensure the establishment of a formal rehabilitation area in which rescuers can be medically evaluated if conditions warrant. Command post adjunct equipment such as a command vehicle, accountability boards, and tactical checklists is also helpful.
Food and liquids must be provided to ensure that rescuers` nutrition and hydration requirements are met. During inclement weather, dry clothing and protective gear for personnel exposed to cold or wet conditions are also needed.
TERMINATION OF INCIDENT
Once the victim has been successfully removed and transported, the trench collapse incident will now move into the termination phase. Although the expediency of operations can slow down during this time, strong management and safe operations must be maintained.
Because personnel have been working for a long time, all personnel should be repositioned from the trench area and allowed to rest and rehab before engaging in any additional operations.
Perform a comprehensive trench reassessment at this time. Evaluate the stability of trench walls and spoil piles and the effects of groundwater or runoff water on the trench. Develop a plan for removing the shoring. Removal should be well-coordinated, and shoring components should be removed in reverse order of their installation. Remove all tools and equipment from the floor of the trench before removing shoring equipment.
This may be the time to coordinate with occupational safety inspectors or other local safety inspectors/investigators–before removing the shoring system. This is also a good time to document rescue activities, including diagrams of the installed shoring system. This information will be helpful for after-action reports, incident critiques, and future training classes.
Environmental control activities must continue during the shoring removal task. Ventilating the trench and monitoring the atmosphere in and around the trench must continue until all rescuers have been removed from the trench area.
LESSONS LEARNED AND REINFORCED
Incident analysis must include information gathering from various sources to determine resource needs and operational mode.
Scene control must include establishing command, traffic, and crowd control; apparatus staging; rescue personnel management; and access control.
Hazards must be assessed and mitigated, and competent shoring systems must be installed by properly trained rescue personnel. Shoring systems must meet OSHA excavation standard requirements.
Rescuers may face various difficult extrication problems. Rescue teams must be prepared for digging, cutting, and lifting scenarios at a trench collapse.
Patient care-givers must administer basic life support as soon as the trench area is properly shored to allow entry.
Trench rescue incidents are long-term operations that require proper support including adequate staffing, rescuer rehabilitation management, and logistics management. n
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Shoring, atmospheric monitoring, ventilation, and ladder access are used to control hazards at this nighttime trench rescue incident. (Photos by author.)
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Rescuers use a pneumatic vacuum tool to remove loose soil.
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(Left) Air-powered chisels were used to break up large boulders that entrapped this construction worker. Rescuers must be prepared to deal with various extrication problems at a trench rescue. (Above) Rescuers prepare to use air bags to lift a large boulder pinning a simulated victim at a trench rescue training class.
ROBERT RHEA is a battalion chief with the Fairfax County (VA) Fire and Rescue Department. He is the program manager for the department`s Urban Search and Rescue Response Team and previously served three years as the department`s director of fire training. He is a principal committee member of the NFPA Technical Rescue Operations and Rescue Technicians Professional Qualifications committees.
