Primary search: Unstable or collapsed structure

Control Measure Knowledge

Personnel should have an awareness of the benefits of urban search and rescue (USAR) attendance at this type of incident, as well as an appreciation of the National Co-ordination Advisory Framework (NCAF).

When attending collapsed structures or buildings initial responders should commence the ‘Six Stages of Rescue’ as an approach to the effective management of the incident until the arrival of USAR resources. Progression through the Six Stages of Rescue takes a considerable time, even at a small, single dwelling collapse. The tactical plan should consider the time and resources required, to achieve a safe and successful conclusion to the incident.

The Six Stages of Rescue, sometimes referred to using the REPEAT mnemonic, are:

Reconnaissance and survey

Elimination of utilities

Primary surface search and rescue

Exploration of voids and spaces

Access by selected debris removal

Termination by general debris removal

On arrival, USAR units will deploy specialist monitoring equipment and collate an audit trail of results of the monitoring, to provide an overview of structural stability.

The Six Stages of Rescue provides a framework to create an operational plan and organise the response to an incident involving an unstable or collapsed structure. While it is likely that there will not be a clear delineation between each stage, and often occasions when stages will overlap, incident commanders should ensure that each stage is completed. This logical and progressive approach maximises effectiveness, particularly during the early stages of an incident.

Each sector will have a defined search phase followed by a defined rescue phase, although these two phases may run concurrently across sectors, depending on the size and scale of the incident.

Stage 1: Reconnaissance and survey

In this stage personnel should:

  • Search the area for casualties, either on the surface or buried
  • Evaluate hazards and the stability of the structure
  • Consider the impact of a rescue
  • Identify potential secondary collapse or movement
  • Gather information about potential casualties in the structure

Immediately after a collapse, the debris of the structure is likely to be very unstable and prone to additional movement. It is important that initial responding personnel adopt stage 1 structural monitoring, with safety officers watching the structure for movement; if possible, photographs should be periodically taken for comparison to track movement.

Emergency responders should assess the nature of the scene and the pattern of the collapse before entering the hazard area, to prevent further movement of the structure and to protect themselves, other emergency responders and casualties. Thermal imaging may provide some information about the location of casualties and potential risks.

Shoring may be required to prevent further movement before entering the hazard area or attempting rescues.

If a structure is damaged leaving it with the potential to move, resulting in secondary collapse, the hazard area should be assessed to identify where the structure will fall. This area should be cordoned off and considered a high-risk hazard area. Access to this area should be restricted to minimum numbers of personnel who have been tasked with implementing control measures such as stabilisation or the removal of overhanging hazards. These personnel should be monitored by a safety officer.

Further information about cordons refer to Incident command – Cordon controls.

The first personnel on scene will have to assess the potential for secondary collapse, but should not be held back if viable rescues can be performed following a risk assessment with level 1 structural monitoring in place. This involves a safety officer being deployed to visually monitor the structure for movement using available references.

Preliminary searches should focus on areas where people were last seen or known to be. Gathering information or intelligence about the last known positions and activities of the people believed to be in the structure will assist planning for rescue activity.

For more information refer to Primary search: All searches, in the section, Gather information from people leaving the incident.

Stage 2: Elimination of utilities

In this stage the utilities should be isolated, from a position of safety if possible, and may require remote isolation. It may be necessary to request assistance from the utility provider. For further information refer to Utilities and fuel – Isolate utility or fuel supply to the premises.

If utilities cannot be isolated immediately, their condition should be continuously monitored and risk assessed. Appropriate control measures should be implemented to protect potential casualties, personnel and the utility systems, and to prevent further or secondary collapse.

Underground mains are susceptible to ground shock caused by the force of a structure collapsing, depending on its size, the cause and the extent of collapse.

Personnel should be made aware that some utility supplies may not have been located and isolated; therefore, they should not cut or disturb the following:

  • Water pipes:
    • Flooding, or a sudden ingress of water, could trap or drown people, for example in a flooded basement
    • The sound of flowing water can interfere with the use of acoustic search equipment
  • Gas pipes:
    • Depending on the type and density, gases could leak into a collapsed structure
    • Some gases, such as liquid petroleum gas (LPG), pool at lower levels in a structure
  • Cables or wires:
    • Non-electrical wiring, such as communications or data cables, can become live after coming into contact with mains wiring

Stage 3: Primary surface search and rescue

During this stage, it may be appropriate to:

  • Withdraw personnel, evaluate progress and review planning
  • Review the command structure, including the introduction of search sectors
  • Seek specialist advice from an urban search and rescue (USAR) tactical adviser (TacAd)

Small organised teams can be systematically deployed to search each sector in specific grids, following risk assessment and implementation of appropriate control measures to minimise the movement of debris. Canine search teams can be particularly effective in undertaking this task.

An agreed marking scheme should be used to indicate:

  • Areas that have been searched
  • Areas that may benefit from a canine search
  • Areas that may contain casualties

The method used for marking should take into account:

  • Its impact on canine search operations
  • Its effectiveness, especially in poor visibility conditions
  • The need for discretion, especially if marking the location of deceased casualties

Potentially, around half of the casualties in a structural collapse may be rescued near the surface of the debris and early in the operation. The initial search should concentrate on the last known positions of people when the collapse occurred. All surface casualties should be removed as quickly and safely as possible.

Secondary collapses can occur without warning, and areas that outwardly appear to be secure may be completely unsupported. Extreme care should be taken during this stage, and personnel should proceed with caution to avoid injury or entrapment.

Stage 4: Exploration of voids and spaces

All voids and accessible spaces created as a result of the collapse should be searched and explored for casualties; this should only be carried out by trained rescue personnel or canine search teams. Voids should be explored visually, by canines and with technical search equipment; an audible call-out system can also be used during this stage.

Around once per hour for a few minutes, all activity should cease to listen for sounds made by casualties; this may include the use of sound detection devices to listen for movement or noise from within the debris.

Stage 5: Access by selected debris removal

Selected debris removal, using specialist tools and techniques, may be necessary after locating a casualty. It may be necessary to limit debris removal to only the obstructions that are blocking access to and rescue of the casualty. Information about the position of the casualty prior to the collapse can assist during this stage.

Stage 6: Terminate by general debris removal

This stage is usually completed when all known casualties have been removed from the debris. However, this stage may need to be delayed if:

  • Information or intelligence indicates there may be further casualties
  • Large amounts of debris are impairing or obstructing operations, which will require heavy equipment or machinery
  • Heavy equipment or machinery cannot be used due to concerns about there still being casualties in the debris

Strategic Actions

Tactical Actions