Blasting FAQ's

Yes, a permit to transport, use and purchase explosives is required before any blasting is performed.

There is no regulation requiring persons to be notified that blasting is occurring in your neighborhood. Each blasting operation is unique. Blasters are required to conduct a pre-blast survey within certain distances to adjoining property.

Call the Fire Marshals' Office if you have a concern about the blasting taking place. Most blasting operations do cause some seismic and air blast vibration. All blasting operations are monitored by the Fire Marshal and do require pre-blast surveys and seismic readings of nearby buildings, within specific distances, to determine safe levels of ground and air movement.

Most of the energy from a blast is used to break rock, but some energy will travel from the blast site in the form of ground and airwaves. Each of these can cause your house to vibrate or shake. 

How a blast feels depends on ground or airwaves that reach your house. These are influenced by the type of blast, the distance from the blast and the amount of explosives.

Your location on the property also affects your perception of the blast. If you are outside a house, you will tend to feel the ground vibrations in your feet and legs. Inside a house, you sense the structure and objects responding to the vibrations. You may also hear objects rattle. This is why you and your neighbors may feel or describe blast vibrations differently.

Typically, blasters are licensed professionals who are required by regulation or by their employers to continually obtain training. They are trained to plan, design, implement and monitor blasts. This training stresses safety in all aspects including protection of your property.

Prior to blasting, pre-blast inspections/pre-blast surveys may be offered to nearby property owners to document the existing condition of buildings and identify any sensitive structures, building components or contents. The site conditions and the inspection information are employed to design the blast to minimize effects to your property.

To ensure that the blasts are working as planned, the resulting ground and airwaves can be measured with a blasting seismograph.

A blasting seismograph measures and records the ground and airwaves from a blast. The information is reported as waveforms, also known as time history records. Time histories show how the strength (amplitude) of the waves varies over time. Amplitudes are reported as particle velocity (inches per second) for ground waves and pressure (pounds per square inch) or decibels for airwaves.

Another important characteristic of the time history is frequency. Frequency is the number of complete waves that pass by in one second. It is reported in cycles per second or hertz. Both amplitude and frequency are needed to describe the motion from ground and air waves.

The blasting seismograph information is used to show compliance with regulations or specified limits and to evaluate blast design performance. Most importantly, it verifies that the ground and air vibrations are within standards set to protect structures.

No. Blasting seismograph data is stored digitally and coded internally to prevent tampering. The data is printed with proprietary software from the manufacturer.

Ground waves change as they pass through different kinds of materials, and in general, the strength (amplitude) decreases rapidly as it moves farther from a blast. This happens regardless of whether they follow the same rock layer or whether that layer changes. As these waves reach your property, your house will be protected if the strength of the vibrations are within allowable limits. These limits are conservatively set to protect surrounding houses regardless of the underlying material.

The foundation is the strongest part of a house. Vibration standards are designed to protect the weakest parts of the house, such as plaster and drywall. Ground vibrations strong enough to crack foundations consisting of concrete and masonry would far exceed the limits set by typical standards.

Vibration energy is not stored in the house and has no potential to be cumulative. Each blast affects your home as a single event and rarely lasts for more than a few seconds. As ground and airwaves pass, the house will begin to vibrate. When the ground and airwaves end, the house will stop vibrating and there will be no further effect from the blast.

This question relates to the concept of structural fatigue, which has been studied by the USBM. In one study, a house was intentionally shaken to find the fatigue limit. Over 50,000 cycles of motion were needed to cause a cosmetic crack. For most blasting projects, the total number of significant ground wave cycles reaching a house is fewer than 1000. Vibration limits have been set accordingly.

The pre-blast inspection/pre-blast survey protects both the homeowner and the blaster by documenting the condition of the home before blasting. After blasting has started, any suspected changes that are found can be compared to the initial condition.

An undocumented crack isn’t necessarily the result of blasting. There are other factors to consider in determining whether blasting caused any crack. For example, environmental effects such as temperature, humidity and wind, as well as homeowner activity may contribute to cracking. On rare occasions, a crack may be the result of blasting if ground or air vibrations exceed recommended standards.

A blasting specialist needs to look at the blast and seismograph records to determine the intensity levels of ground and air vibrations at your home. Based on the estimated or recorded vibration levels at your house, as well as other factors, it can be determined whether blasting could have been responsible.

SINCE BLASTING DIDN’T CAUSE THE DAMAGE, THEN WHAT DID?

There are many possible causes. Every day, construction elements of your house shrink and swell from environmental changes. And movement occurs from human activities such as opening and closing doors and windows, hanging pictures on a wall or simply walking through the house.

Continued research has shown that changes in temperature, humidity and soil moisture can yield greater changes to a structure than ground and air vibrations from a blast that are within recommended standards.

Pets, like humans, are sometimes startled by the sound of a blast or warning signals, just as they might be startled from thunder. Like humans, animals are subjected to a variety of vibration sources and events each day with no long-term effect.