Blasting at the Bath Plant
At the Bath cement plant, the blast design has been refined and improved over the years to make the operation as safe as possible, control the impact on neighbors, and reduce the cost of blasting.
The main material required to produce cement in the kiln at the Bath Plant is limestone rock, which is quarried at the plant.
The only way of breaking the bedrock into sizes that can be handled and crushed is through the use of explosives, loaded into predrilled holes. A row of holes is drilled at a predetermined spacing and burden (amount of rock in front of the hole). Within each hole, the explosive is divided into three decks, each of which is separated by crushed stone. Each deck of explosive is fired at a slightly different time. This creates a series of small explosions, instead of one large one, reducing the magnitude of the resulting vibration and helping to control the movement of the rock as it comes off the face.
The blasts at the Bath Cement Plant are designed to minimize the effects on adjacent neighbors, but the ground vibration and airblast will definitely be noticeable. Detailed measurements by the three seismographs used during each blast have shown that the levels are well below the threshold where damage could occur.
If you are concerned about the level of disturbance at your property, please contact us and we will arrange to take measurements directly on your property during a future blast. Blasts occur approximately once a week, at either 11:30 or 1:30. If you would like to be informed on the day of the blast, please contact the plant and we will add your name to our blast notification list.
West Quarry Development
The Bath Plant is opening our new West Quarry! This move is due to decreasing stone quality in the current quarrying location. On April 18, the Bath Plant held an information session to keep our neighbors up to date on this new development. The information presented at this meeting is attached below for reference.
Q: What is Ground Vibration?
A: Ground Vibration is the shock wave from the blast creating a series of small vibrations as it moves through the nearby ground. The size of the shock wave depends on a number of factors, but the main one is the amount of explosive detonated at any one instant. This is the most important reason why the explosive in each hole at the Bath quarry is divided into three smaller blasts and why each hole is fired at different times.
Q: How much Ground Vibration is necessary to cause property damage?
A: Many years of research and testing have shown that ground vibration must be greater than 50 mm per second to cause any damage to nearby structures. Even at levels of 50 mm per second the damage caused is usually very superficial - such as small cracks in plaster. Much higher vibration levels are required to cause major structural damage. Current regulations in Ontario limit blasting-induced ground vibration to 12.5 mm per second at the nearest private receptor or structure. Ground Vibration measured during blasting is well below this limit.
Q: How do you measure Airblast?
A: Airblast is measured in decibels (dB). A decibel is a logarithmic unit of measurement used to express noise levels. A logarithmic scale is used to convey a large range of data in a more manageable range. For example, a difference of three decibels represents a doubling of sound intensity. In Ontario, the limit is 128 dB (linear) at the nearest private residence to the quarry. Again, this is far below the level that will cause damage (around 150 dB) but it can be annoying and frightening, especially if it is unexpected. Generally any level above 120 decibels is noticeable to residents, particularly if they are inside the residence. The level of airblast can change significantly due to weather conditions, allowing people to experience a stronger airblast than they would normally notice.
Q: How do you monitor the levels of Ground Vibration and Airblast created?
A: Ground vibration and airblast are measured using modern seismographs to ensure compliance with the law and to improve blasting results. Measurements made at the nearest residences to the Bath Cement Plant consistently show vibration levels well below 5 mm / second and airblast levels below 120 decibels, although there may be days where the atmospheric conditions (wind, cloud cover and temperature inversions) may make the airblast stronger at some locations. A nearby observer will feel the ground vibration before the airblast - this is usually the easiest way to know which effect they are experiencing.
Q: How do I know that the Blasts are not Damaging my Home?
A: The blasts at the Bath Cement Plant are designed to minimize the effects on adjacent neighbours, but the ground vibration and airblast will definitely be noticeable. Detailed measurements by the three seismographs used during each blast have shown that the levels are well below the threshold where damage could occur. If you are concerned about the level of disturbance at your property, please contact us and we will arrange to take measurements directly on your property during a future blast.
Q: When do the Blasts take place?
A: Blasts occur approximately once a week, at either 11:30 or 1:30. If you would like to be informed on the day of the blast, please contact the plant and we will add your name to our blast notification list.