Demolishing a building involves many of the same hazards as constructing one. But demolition projects that use explosives create another set of safety hazards that need to be addressed. One of the most crucial of these is preventing harm to workers or the public by projectiles, hazardous materials or falling debris. And the best way to accomplish this is by establishing and securing an exclusion zone for the day of the blast and then ensuring that everyone, except perhaps the shot-firer, is outside the exclusion zone when the blast occurs.
Planning an Exclusion Zone
A properly planned exclusion zone consists of four areas:
- Plan area: The physical location of the structure being demolished
- Designated drop area: This includes the plan area and the area where most of the debris will fall.
- Predicted debris area: This is the furthest area outside the designated drop area where debris is expected to land
- Buffer zone: An area beyond the predicted debris area and the outer perimeter of the exclusion zone
Assess the size of each area individually based on the hazards identified prior to the blast. This assessment should include factors other than just the height of the building, such as the types and location of explosives being used. In general, the following factors come into play:
- Planned collapse mechanism
- Materials used in the original construction and any modifications of the structure since that time
- Charge weights, location and detonation sequence
- Integrity of the detonation system
- Any pre-weakening of the structure
- The degree of blast protection in place
- Possible “slap effect” due to the impact of falling debris on the designated drop area
- Ground vibration, surface shock wave or air overpressure
- Dust and aerosolized debris**
**Note: The initial assessment of the structure should include an inspection for hazardous materials, such as asbestos, lead, silica, polychlorinated biphenyls (PCBs) and other heavy metals or chemicals that could be dispersed by the blast. You must safely remove or mitigate all hazardous materials before demolition can take place.
Establishing the Exclusion Zone
After establishing the parameters for the exclusion zone, planning focuses on ensuring that no one is inside the zone on the day of the blast. It may be helpful to use established landmarks such as streets, pathways, waterways or buildings to define the zone. If these fall outside the planned area, consider widening the perimeter if doing so makes sense from the standpoint of safety. For example, it may be easier to cordon off and police a street or a drainage canal than to enforce an imaginary “line in the sand.”
If evacuation of nearby structures is necessary to create an effective exclusion zone, you may need to involve law enforcement to effect the removal of citizens from the area on the day of the blast. This, too, should be planned and coordinated well in advance. Informing the public of when the demolition will take place can help the project go more smoothly as well. It may also be helpful to post signage about planned detour routes if the demolition will disrupt normal traffic flow.
At the Carmoon Group, we have been serving the construction industry for over two decades. We provide comprehensive, targeted insurance solutions for construction professionals in every one of the construction trades, including environmental contractors and those who specialize in demolition. Give us a call today to schedule an appointment for your insurance review or, if you prefer, reach out online. We’re confident that we can provide you with a comprehensive insurance program that will meet your needs at a price you can afford.