Q. Why does rock excavation need to take place to proceed with the Trillium Line South Extension?
Rock excavation needs to take place in three main locations along the existing Trillium Line. The first location is north of Gladstone Avenue and this is needed to allow construction of the new station. The second area will occur beside the existing Carling station and this is needed in order to lengthen the existing platform to accommodate the longer trains. The final and longest stretch will take place in the trench from the south side of Gladstone Avenue to Beech Street. This work is required so that the guideway can be widened to allow for the installation of a second track.
Q. Why do you need to “blast”, why can’t the rock be dug out?
The use of highly regulated and controlled explosives and detonating accessories allows the rock to be excavated efficiently. While rock blasting creates intermittent disruption (noise and vibration), it is considered much less impactful to area residents than the other available method, called hoe ramming, which involves using large equipment to chip out rock and creates loud noise, vibration and dust and is quite disruptive. The overall excavating operation period is greatly reduced through the use of controlled blasting.
Q. What experience does the blasting company have?
TransitNEXT, the City of Ottawa’s contractor, has retained M-Roc Ltd, an Ottawa-based precision blasting contractor that has been the primary blasting contractor in downtown Ottawa for over 20 years. Projects they have worked on includes blasting at Parliament Hill, the World Exchange Plaza, the Museum of Civilization (beside heritage structures) and for condominium underground parking garages in downtown Ottawa.
Q. What qualifications must a rock blaster have?
Blasting is a highly specialized occupation that requires training and knowledge of the storage, transportation and field application of explosives and detonation accessories. Blasters are certified and work under the supervision of a Professional Engineer. Blasting is regulated by the provincial government.
Q. I live very close to the blasting site. I am very concerned about potential damage to my property because I am so close to the blasting.
Explosives are commonly used in very close proximity to man-made structures. For example, controlled blasting is done to create swimming pools next to existing homes, utilities are installed beside roads and buildings, and foundations are built in developed areas.It is the level/frequency of vibration that causes damage to structures, not the distance from the building/structure. Regulations have been adopted to ensure that vibration levels are lowered the closer the blast is to the existing structures.
Q. How do you know what a safe level of vibration is near homes?
M-Roc Ltd. will be following a strict set of specifications outlined in both the Trillium Line Extension Project Agreement and the City of Ottawa’s Special Provision F-1201. The vibration limit criteria in the City’s Special Provision is based on data from the U.S. Department of Mines, which has performed thousands of research studies on blasting near structures. These regulations dictate the acceptable limits on vibrations in order to protect the nearby structures.All blasts are designed to meet regulatory limits and are monitored by an independent monitoring company to ensure compliance with these limits.
Q. How will you know if the vibration level is safe during blasting?
Blasting seismographs will be placed near properties close to blasting. These seismographs measure and record the ground and airwaves from each blast. This information is used to verify that the ground and air vibrations are within the standards set to protect local structures. This data is reviewed with each blast and is independently recorded to demonstrate compliance. Should readings approach the set limits, blasting activities are put on hold until the vibration levels can be better controlled.
Q. Where will seismographs be placed?
Seismographs are strategically placed by Explotech Consulting Engineers who select the most optimum location to record vibrations. It will not be necessary for a seismograph to be placed at each property. One seismograph will monitor and record vibration levels in the neighbouring buildings as well as the building that it is near.
Q. Can the data on a seismograph be altered?
No. Blasting seismograph data is stored digitally and coded internally to prevent tampering.
Q. Why don’t you monitor the vibrations inside my house?
Research has shown that the most consistent way to measure ground waves is to attach the seismograph to the ground outside the property. The measured vibration level can then be compared with vibration regulations.
Q. Will the blasting vibration damage my foundation?
The foundation is the strongest part of a house. No matter what your foundation is made of, vibration regulations and standards are designed to protect the weakest parts of the house, such as the plaster and drywall. Ground vibrations strong enough to crack foundations consisting of concrete and masonry would have to greatly exceed the vibration limits set by typical regulations.
Q. Is there a greater risk of damage with repeated blasts near my property?
The United States Bureau of Mines has studied the repeated effect of vibration on structures. This study included continuous, daily blasting for 28 years. The goal was to investigate the cumulative effects of blasting on a building. They concluded that, as long as the vibration levels were below regulated limits, cumulative or repeated effects were not seen.
Q. Is there any danger from flying debris created from a blast?
Layers of heavy blasting mats are used with every blast to prevent flying debris. Each blast is actually made up of a series of small blasts that are sequenced to reduce the risk of any flying rock and keep vibration levels to a minimum.
Q. What will I hear and feel during blasting?
A series of air whistles will be sounded before and after a blast:• 5 short whistles will sound 1 minute before a blast• 3 short whistles will sound immediately prior to a blast• 1 long whistle will signal the all-clear after a blastPeople (and animals) are very perceptive to a small amount of ground motion.However, without scientific instruments, people cannot accurately put a value on the amount of motion that is created. Homes take quite a lot of vibration on a daily basis. Door slamming, thunderstorm activity and wind all produce vibrations that we feel and take for granted since these are everyday events. The level of vibration from controlled blasting will be similar to these types of events.
Q. Will some of the blasts feel stronger than others?
The position and orientation of a blast at a construction site may cause the perception that one blast is stronger than another. Your location (outside, inside, upper, or lower floor of your house) will also change your perception. Human perception is not a good measure of blast effect, which is why seismographs are used to scientifically measure vibration.
Q. How long after blasting can my house be affected?
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 vibrate. When the ground and airwaves end, the vibration will end.
Q. How will you know if my house has been affected?
Prior to blasting, pre-construction surveys are offered to nearby property owners to document the existing condition of the building and identify any sensitive structures or building components. Notifications are being delivered to homes within the impact zone and these exterior surveys are currently being completed in stages by DST Consulting Engineers. If you have not yet had a survey done but you would like to schedule an appointment, please contact the project coordinator at 613-858-2287 or via email at email@example.com.In addition to pre-condition surveys, seismograph data before and after each blast helps ensure that vibration levels are within set limits to prohibit damage to nearby structures.
Q. Is there anything I should do to prepare for blasting?
You may wish to check picture frames and wall-hangings to ensure they are secure, as it will be difficult to make a claim for such damages.
Q. What if I find damage, who do I speak to?
Although all measures are taken to prevent damage to neighbouring properties, you may contact the vibration monitoring company or the blasting company if you wish to file a damage complaint. A successful claim is not common as long as vibration readings are within allowable vibration limits.
If you have any additional questions or concerns, please contact the City’s representative:
Stakeholder Relations, Rail Construction Program
City of Ottawa
Email: firstname.lastname@example.org | Website: ottawa.ca/stage2