Frequently Asked Questions – Blasting Operations

Q: What is blasting and why is it happening in Almonte? 

A: Blasting is a method used to break rock or hard earth so that it can be easily removed with excavation equipment. The most common method of blasting is where the Blaster drills holes 2 – 5 inches in diameter deep into the ground and fills the holes with explosives. The explosives are detonated fracturing the rock, which can then be removed by an excavator. The people who undertake blasting are licenced professionals who work for a company which specializes in the use of explosives for mining, quarry, and rock removal operations. These professionals are call Blasters. 

There is currently blasting happening as a part of the excavation works in the Weavers Way Subdivision. Blasters are clearing the bedrock in the area to prepare for the installation of watermains, sewers, and the construction of homes.  

Q: Should I be worried about my personal safety while blasting is happening?  

A: The blasting that is occurring in the Weaver’s Way Subdivision does not pose a serious risk to public safety. The construction site is continuously monitored by the contractors and their staff to ensure that no one has access to the areas where blasting is occurring. In addition, the Blasters are using blast mats to cover each and every explosion. These blast mats are 8,000 to 10,000-pound rubber mats made of recycled tires which are placed on top of the explosive filled holes prior to detonation. The mats act to catch any loose rocks and prevent them from being thrown off the property.  

Q: Why can I feel the ground shake when the blasting is occurring? 

A: When explosives are detonated in the ground to fracture rock, most of the energy goes into breaking the stone; however, some of that extra energy transfers into the solid ground creating ground vibration. Ground vibrations are what you can feel when blasting is occurring. These vibrations can shake trees, roads, houses and anything that is attached to, or is sitting on, the ground. Humans are especially sensitive to these vibrations and can easily feel the faintest ground movements caused by the vibrations.  

Q: Can ground vibrations from blasting cause damage to my house? 

A: It is very unlikely that a home will be damaged by ground vibrations caused by blasting. While the vibrations from blasting are easily felt by someone in a home, the magnitude of the vibrations is not typically high enough to cause any structural or foundation damage. The vibration levels are monitored by the Blasters so that they can ensure that the ground vibrations are below the limits where damage could occur. The most common form of damage to a home near blasting operations is cosmetic damage such as cracking in drywall or stucco.  

Q: Why do my windows and door shake when a blast happens? 

A: When an explosion of any kind happens, it compresses the air around it and sends a wave of pressurized air into the surrounding area. This is known as air overpressure or a blast wave. The intensity of a blast wave changes due to many environmental factors such as cloud cover, wind direction and windspeed. This blast wave is what causes windows and doors to shake after a blast. The blast wave presses against the exterior of a house like wind; however, it dissipates very quickly which causes windows and other loose items to shake. During controlled blasting this pressure is measured by the Blasters to ensure that the blasts are not exceeding the limits set by the province.  

Q: Who sets the limits for blasting and is there a regulation that the Blasters must follow? 

A: The standards that guide blasting work in Ontario is the Ontario Provincial Standard Specification 120, Use of Explosives (OPSS.MUNI 120). This standard has been created by the Province and is enforced by the Municipality. It regulates the use of explosives in construction and other activities within Ontario.  

Other pieces of legislation and guidelines affecting blasting operations in the Municipality and throughout Ontario and Canada are: 

Q: If there is blasting near my house, will I be notified? 

A: Yes, as per the OPSS.MUNI 120 standard there are notification requirements which requires certain information to be included in the notice, such as when blasting is going to occur, a simple schedule, general information about the blast warning system and contact information for the Blaster or contractor.  

Q: What is a pre-blast inspection and why did I receive an inspection offer and my neighbours did not? 

A: A pre-blast inspection is an inspection completed by a third-party inspector that documents the condition of a property, house, structure, or utility prior to the commencement of blasting operations nearby. This is completed before blasting occurs, so that in the event that there is an issue or damage to a property, which may have been caused by blasting, the property owner can contact the third-party inspector who will reference the inspection to determine if the damage or issue existed prior to the blasting occurring.  

If you received a notice offering a pre-blast inspection and your neighbour(s) did not it is likely because your home is within a blast radius, which is determined before the blasting has taken place.  

In accordance with the OPSS.MUNI 120 standard, if a Blaster is drilling blast holes that are less than 5 metres into the ground, then the Blaster must offer inspections to all properties within 75 metres of the blasts. If the blast holes are deeper than 5 metres, the Blaster must offer inspections to all properties within 150 metres of the blasts. For the Weaver’s Way subdivision, the blast holes are less than 5 metres deep, which means that the 75-metre inspection radius applies. 

Q: Why are there no warning signs? 

A: It is not a requirement of the regulation to have warning signs posted alerting of blasting operations. The construction site is monitored by construction contractors and their staff and there are protocols in place which limit access to the site to ensure safety.  

Q: What is the Municipality’s role? 

A: The Municipality is closely involved with the development in Weaver’s Way and is an active participant in discussions regarding blasting and the ongoing excavation and earth works on the site. Staff have been engaged in discussions with the contractor and Blaster on the distribution of notices and vibration monitoring for the project. In addition, municipal staff have reviewed the current blasting procedures and the alarm system to ensure that both meet the minimum requirements of the OPSS.MUNI 120 standards.  

During blasting operations, municipal staff regularly review the vibration and air overpressure reports to ensure that they are compliant with the OPSS.MUNI 120 standards.  

Municipal staff are available to discuss concerns from residents and to explain the blasting process. The goal of the Municipality in this process is to ensure that residents are confident that appropriate measures are in place to protect them and their property.