Blasting is often the most efficient and cost-effective method to facilitate rock excavation.  In many cases, no good alternative exists.  Alternatives would require the use of noisy heavy machinery which may have to operate for weeks to complete the work accomplished by a single blast.  If you are in a neighborhood and blasting is being conducted nearby, it is likely that blasting was used to develop your neighborhood as well.

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 air waves.  These waves spread out from the blast much like waves from a pebble dropped in a pond.  Both the ground waves and air waves can cause your house to vibrate or shake.  Humans are very sensitive to all such vibrations.  If you are outside a house, you will tend to feel the ground vibrations in your feet and legs.  When inside a house, you feel and sense the structure and objects around you responding to the vibrations. You may hear windows and dishes rattle and hanging objects may swing.  It is possible that you may feel or hear your house shake from blasting even at very low levels.  You may be surprised to learn that the actual amount of ground movement (or ground displacement) is no greater than the width of a single sheet of paper, yet these minor movements sometimes can be strongly felt.  Not all blasts will feel the same.  Some blasts will be more noticeable than others.  

It is possible to feel vibrations from blasting without hearing anything.  Ground vibrations may be independent of sound and the dominant frequencies of air overpressure waves are below an audible level.

Many factors affect the perception of the sound of blasting.  The sound depends on your distance from the blast, the amounts and types of explosives used per hole, the depth of the charges, the type of cover used, and so on.  When blasting, sharp reports may be heard, as well as loud and/or low rolling rapid fire rumblings.  Regulatory limits are based on a scale related to air pressure and not based on a measure of sound.  The regulatory limit set by the USBM is 133 dB(L).  A measurement in dB(L) should not be confused with dBA which is a weighted overpressure scale intended for measuring the human auditory experience.

The regulatory limit defined by USBM for air-overpressure is 133 dB(L).  Damage to old or poorly glazed windows does not occur until air-overpressure reaches about 150 dB(L) which, based on the logarithmic  dB(L) scale, is over seven times higher than the USBM limit.

Unfortunately, we cannot warn our pets about an impending blast and they may be startled or frightened by the sound of warning signals and blasting sounds and vibrations just as they may be startled by thunder.  

Blasting does produce a ground disturbance that results in the release of dust particles.  Most of the particles fall to the ground within the blasting zone but dust can migrate from the blasting area especially on windy days.

All blasting activities conducted by Quality Drilling and Blasting meet all Federal and State requirements.  Approved blasting permits will be in place prior to blasting in municipalities where they are required.  All blasting is conducted under the direction of the Blaster-in-Charge.

The blasting company provides notifications to nearby neighbors and may post information at the construction site.  Should your home be outside the notification area, or if you were not able to receive the notification, you may be unaware of the activity.  Typically, an email will be sent to members on a blasting notification list informing them of the immediate blast schedule.  Local municipal requirements may stipulate a specific time frame for individual blast notifications to be made, often within 24 hours of the planned blast.  You may request to be added to the notification list.

Often, residents are unaware of pre-existing cosmetic damage which they may attribute to blasting when critically inspecting their home following a blast.  For this reason, homes within a prescribed distance are offered pre-blast surveys to document pre-existing conditions in order to identify new changes.  A pre-blast inspection/pre-blast survey is a visual survey that documents the visual pre-existing condition of a residence or other structure.  Photos, video, and/or notes may be taken to document the visible condition including existing cracks and defects.  The inspector does not move furniture, inspect crawl spaces, roofs, or other areas difficult to access.  This survey protects both the homeowner and the blaster by documenting the condition of the home before blasting.  After blasting has occurred, any suspected changes that are found can be compared to the pre-blast documentation.

The pre-blast survey is a visual survey that covers accessible areas.  Since the weakest materials are the most susceptible to blasting damage, the survey focuses on those cosmetic materials.  Access is typically difficult under the house and the structural elements under the house are stronger than cosmetic materials, thus not susceptible to typical blast energies.

A blasting seismograph is set up prior to a blast, usually by an employee of the company conducting blasting or by a third-party consultant. The seismograph is normally placed near a structure closest to a blast.  Having a seismograph placed on your property provides real time documentation of the ground and airwave energies reaching that location.

Blasting seismographs record ground and airwave vibrations.  The recording begins once vibrations have reached a minimum threshold referred to as the trigger level. This level is set low enough to detect the blast vibrations, but high enough that it will not accidentally record non-blast vibrations (such as nearby human activity). Once triggered, the data is recorded and stored in the seismograph and it cannot be altered.

Vibrations are more disturbing to the occupants of a structure than they are disturbing to the structure.  The likelihood of blasting damage cannot be estimated by the perceptions of occupants in a building during the event.   Higher frequency vibrations within the recommended safe limits can be more disturbing to occupants yet less disturbing to the structure.  Seismic monitors are deployed to measure actual ground motions and air waves.  This data is used to evaluate the intensity of the vibrations and determine compliance with vibration standards.

Hertz is a count of the number of cycles per second of a waveform, which is a frequency.  Particle velocity and peak particle velocity (PPV) are measures of the speed at which a particle of ground is moving.  PPV is the maximum speed at which a ground particle moved during the period of monitoring.  It has been found that PPV is the most predictive scalable measurement relatable to blasting damage.

A USBM research report titled USBM RI 8507 “Structure Response and Damage Produced by Ground Vibration From Surface Mine Blasting” recommended the frequency-based limiting criterion known as the Z-Curve.  The concept of structure response provides the foundation for frequency-based limits.  The recommended limits were developed for the prevention of threshold cosmetic damage in structures in the most susceptible of materials such as plaster and drywall.  Other materials such as masonry, concrete block, concrete pads, and foundations can withstand much higher levels of vibration without damage.

Residential structure response to blast vibrations has been researched extensively (Including USBM RI 8507 and RI 8896).  The general types of structure response caused by external vibrations are:

Foundation Structure Response refers to structure vibration below the ground level and is equal to the incoming ground vibrations.

Whole-Structure Response (or the racking motions) involves the above ground part of the building that responds to frequencies of 4 Hertz to 12 Hertz.

Mid-Wall Response (or motions within individual panels or components above ground, normally out of plane with walls) is the part that is responsive to frequencies of 12 Hertz to 20 Hertz.

In the whole structure response, the above ground portion of the structure is free standing and moves in response to the below ground portion which moves with the ground.  Differential motions between the upper and lower corners of the structure cause racking responses.  Mid-wall responses are typically responsible for window rattling, picture tilting, etc.

Frequency is a component of ground vibrations that affects how structures respond. When the vibration frequency closely matches a natural or fundamental frequency of a structure or structural element, the structure or element will tend to respond more vigorously and the incoming ground vibrations will be amplified in the upper portion of the structure. Alternatively, if the ground vibration frequency does not match the natural frequency, very little seismic energy transfers into the structure, and there will be little, if any, response.  Buildings tend to have a low natural frequency and will be more responsive to low frequency ground and air vibrations.  As can be seen in Figure 1, the Z-curve takes this into account and reduces the acceptable PPV at lower frequencies in order to protect structures.  When blasting in proximity of buildings, blast plans are designed to keep lower frequency vibrations within the lower PPV limits as established by the USBM in order to prevent damage.

The two scales are not related and cannot be interchanged.

A blasting seismograph reports how much the ground vibrates at one particular location.  It measures the intensity of ground motion. The intensity will be stronger closer to a blast and weaker at a distance. 

The Richter Scale reports the power of an earthquake or its magnitude. It is an estimation of the energy released at the source.  Earthquake scientists do use seismographs to measure the intensity of the ground waves at different locations and then calculate a Richter Scale magnitude. This value is based on two things: how far the seismograph was from the earthquake and the intensity of the ground waves at numerous seismograph locations.

Some reports say 3 years, some say 10, but the truth is it may never stop settling!  Foundation settling takes place naturally over a period of time and is impacted by the weather and climate.

How a blast feels depends on the ground and/or airwaves that reach your home.  Your perception of the blast is affected by the direct vibrations you feel, combined with response of the structure and objects around you.  You may hear windows and dishes rattle and hanging objects may swing.  Even though you may feel and hear a seemingly strong structure response while inside the house, you cannot determine the likelihood of damage based on these responses.  A well-designed blast will result in vibrations which are below the threshold that causes damage even to the weakest elements of the home.  

Some people who have experienced earthquakes find blasting vibrations to be more disturbing than earthquakes.  Blast vibrations feel different.  This may be due to comparing low frequency vibrations of an earthquake with the higher frequency ground vibrations and associated airwaves that are produced in blasting.  Other people who have been in earthquakes consider blasting vibrations to be a minimal disturbance.   

Floors and doorways are typically impacted by higher levels of localized stresses during normal daily household activities than what they will be subjected to during blasting.  Blasting vibrations affect the building as a whole unit whereas daily activities, such as opening/closing doors and walking across the floor, cause localized stresses in the structure.  Floors and doorways are built of strong materials in order to withstand these daily stresses. The first materials to succumb to blasting vibrations are the weakest materials.  Drywall, lath, and plaster have been found to be the weakest materials and are the first materials damaged when impacted by adverse blast vibrations.  If floors and doorways were to become damaged by blasting, conspicuous drywall and plaster damage would be expected to be associated with it as well.

The first step is to have a blasting specialist evaluate the blast and seismograph records to determine the intensity levels of ground and air vibrations at the location.   Based on the information gathered, an inspection of the structure and cracks may be conducted.  Often, what is believed to be recent blasting damage is actually a pre-existing condition or an issue unrelated to blasting.  From these factors, it can be determined whether blasting could have been responsible.  Should blasting be determined to be the cause of damage, arrangements will be made for repair.

Blasting damage is caused by strain experienced in materials at the moment the vibrations are acting on the material.  Vibration energy is not stored in the materials or structure.  Once the vibrations have abated, no further forces from blasting will be acting on those materials.  Blasting damage would occur only at the time of the blast.  Foundations represent the strongest material in the building.  Foundations cannot be damaged without extensive damage to weaker materials in evidence.

There are many possible causes of cracks in drywall. The construction materials in your house shrink and swell due to environmental changes every day.  Movement affecting the home can be caused by environmental forces, ground settlement, and human activities such as opening and closing doors and windows, hanging pictures on a wall, or simply walking through the house.  These forces can cause stress which results in cracks in drywall, plaster, and stucco finishes.

Often residents are unaware of pre-existing damage in a home which they may attribute to blasting when critically inspecting their home following a blast.  Homes within a prescribed distance of blasting are offered pre-blast surveys to document pre-existing conditions in order to clearly identify recent changes that could be attributable to blasting.  If there is concern regarding possible blasting damage, contact the blaster.  A blasting specialist can evaluate the blasting and seismograph records to determine the intensity levels of ground and air vibrations at your home.  Additionally, an inspection of the damage and the structure may be conducted.  From the collected data, it can be determined whether blasting could be responsible.

The intensity of ground and air vibrations from blasting diminishes with distance from the blast site.  It is rare for a home farther from the blast to experience damage when homes closer to it do not.  Often residents are unaware of pre-existing cosmetic damage which they may attribute to blasting when critically inspecting their home following a blast.  Homes farther away have not been pre-blast surveyed and homeowners may not be aware of pre-existing conditions.  If there is concern regarding possible blasting damage, an investigation can be conducted.  A blasting specialist will evaluate the blast and seismograph records to determine the intensity levels of ground and air vibrations at your home.  An inspection of the damage and the structure may be conducted.  From these factors it can be determined whether blasting could have been responsible.

Fly rock is a hazard that is associated with blasting.  The Blaster-in-Charge will take the precautions he determines appropriate to prevent fly rock from being propelled outside the blasting zone.  Even so, an area will be cleared by the blaster to keep persons, animals, vehicles and equipment outside of the hazard zone.  The blast will not be triggered until the blaster is assured the area is clear.  If blasting is taking place close to susceptible structures such as a residence, additional precautions are available to control fly rock.  With proper precautions, fly rock should not impact the home.

Blasting accidents resulting in unintentional detonation of blasting agents are rare in the US.  Modern blasting agents, professional training, and blasting safety practices work together to minimize opportunities for an unintentional detonation.  Initiation components are kept separate from other blasting agents to eliminate the possibility of detonation during transport and blast preparation activities.  A shot is not “tied-in” until after holes are loaded.  The initiator is tied in by the Blaster-in-Charge immediately preceding the blast and after he has determined it is safe to do so.