Saint-Grégoire mechanical ventilation station

Virtual information session

You can view the recording of the virtual information session, which took place on March 16, 2021. The summary of the questions asked by participants at the virtual information session and the answers that we gave is available below (Impact on local residents section)

View the recording

Construction of the Saint-Grégoire mechanical ventilation station

Project summary

The construction of the Saint-Grégoire mechanical ventilation station, located on the street of the same name, is part of our program to refurbish our métro facilities and equipment. The new building will be located in the parking lot of the École des métiers de l’équipement motorisé de Montréal.

Duration of the work: December 7, 2020 to summer 2023

Description of the work: Construction of a new mechanical ventilation station

Métro impacts: No

Bus impacts: No

Impact on customer trips

The project has no impact on customer trips.

Impact on local residents

Texte important

News from the worksite

We wish to inform you that work will continue at the Saint-Grégoire mechanical ventilation station worksite on Saturday, September 11, from 10 a.m. to 6 p.m., in accordance with municipal by-laws. The excavation work is carried out with a hydraulic rock breaker to split the rock.

You can view the recording of the virtual information session, which took place on March 16, 2021.

View the recording

The ventilation station supplies and extracts air. The air extracted is from the métro.

No. The BNQ 1809-350 specification exists to regulate blasting work and make it as safe as possible. We are following this specification to reduce the chances of a CO leak at the source. The standard requires that alarms be provided only to residents within 100 metres of the worksite. Therefore, there is no reason to distribute alarms to people living more than 100 metres away.

Repercussions on building foundations are very unlikely. Any repercussions that did occur would be noticed immediately, not years later. If your building is located within 50 metres of the excavation site, it will be inspected before the start of the work.

If you live within 100 metres of the excavation site, the firm Gestion Monox will contact you to install CO detectors. This firm is responsible for determining where the alarms should be installed in each building and explaining to you how they work.

The work is progressing very well, and no delays are expected at this time. In fact, the contractor is currently ahead of schedule. In the event of a delay, the STM is able to penalize the contractor.

The vibrations will be controlled and must comply with very strict standards, making them unlikely to damage nearby buildings. If you think that any damage has been caused by the work, you can file an official complaint by contacting our customer service. A claim file will then be opened with the contractor’s insurer. Click here to learn how to contact us.


Buildings within 50 metres will be inspected. This radius was determined by an independent consulting firm hired by the STM to ensure that the zone be defined as objectively as possible.


Start of excavation

We will start digging in late February 2021. First, we will use a hydraulic rock breaker to dig the 18-metre-deep vertical shaft.

Then micro-blasting will be used to excavate the underground part of the ventilation station, starting on May 4, 2021.

  • The construction site has already been fenced off, and the micro-blasting will be done within its perimeter. Noise screens have also been installed.
  • Blasting mats will be installed over the rock to contain the micro-blasts.
  • Safety instructions will be posted around the site.
  • No explosives are stored on site.
  • A professional firm specialized in monitoring vibrations has been mandated to ensure compliance with the standards established by the City of Montréal and the STM.
  1. 12 whistle or siren sounds
  2. 30-second wait
  3. Micro-blast
  4. One long whistle or siren sound
  5. End of blasting

Micro-blasting began on May 4, 2021 and continue until spring 2022. We will start with two to three micro-blasts a week, then increase it to one to three a day each week.

Close to the worksite, residents may feel vibrations or hear noise when the micro-blast goes off, which is totally normal.

Micro-blasting can produce carbon monoxide. There is a risk of CO leaking through the underground portions of buildings, but this is highly unlikely. The distribution of carbon monoxide indicators in buildings within 100 metres of the worksite is a preventive measure in accordance with recommendations from the ministère de la Santé et des Services sociaux.

As a safety precaution, Gestion Monox Inc. has been mandated to distribute carbon monoxide indicators to buildings within 100 metres of the site.

If your property is located in the targeted area, Gestion Monox Inc. will contact you shortly.


Any construction work likely to generate noise will be scheduled during the hours allowed by municipal regulations, 7 a.m. to 7 p.m., Monday to Friday, and 10 a.m. to 6 p.m., Saturday, inclusive


While the majority of the work will take place Monday through Friday, it may be necessary for it to continue on Saturdays and possibly, but more rarely, on Sundays in order to meet the project deadline. Should this happen, any extensions will be announced on this page, and an electronic newsletter will be sent out to subscribers.


Anti-dust sheets will be installed on the worksite partitions.


Once the work is complete, we will create a small grassy area near the new building to make it more inviting. Three park benches will also be installed on site.

The worksite is a considerable size. We have to dig into the rock bed to create a vertical shaft to a depth of 21 metres. We will then excavate a 64-metre tunnel, removing a total of 6,790 cubic metres of bedrock from the site. After that, we will install a waterproofing membrane over the tunnel to protect it from water infiltrations. Next comes the concrete, which will form the tunnel and underground building. Finally, fans and their accompanying electrical equipment will be installed. All of these steps vary in terms of duration and impact, such as noise and dust.

Once the work is complete, the mechanical ventilation station will comply with all City of Montréal noise by-laws. Huge noise suppressors will mitigate the noise from the fans, installed below ground level, to ensure quiet for residents living nearby. The noise will not exceed 50 decibels, a level comparable to that of a household dishwasher.

Learn more about the project

A mechanical ventilation station is a large infrastructure located between two métro stations that is equipped with two powerful fans designed to extract hot air from the métro system through inlets fitted with air vents. Ventilation stations built for the original métro system extract around 60,000 cubic feet of air per minute, while the new ventilation systems extract around 240,000 cubic feet per minute. Huge noise suppressors mitigate the noise from these fans to ensure quiet for residents living close to a ventilation station.

  1. Preparation of worksite
    Fencing off the worksite
    Setting up the worksite and installing equipment
  2. Excavation at ground level
  3. Excavation in the rock bed
    First, we will use a hydraulic rock breaker to dig the vertical shaft. Then, we will switch to micro-blasting to excavate the horizontal portion. This method was chosen by the contractor for tunnel excavation as the fastest and most efficient way to dig horizontally, so that the work can be finished as quickly as possible and with minimal impact on local residents.

    Urban micro-blasting is a safe, well regulated technique that we use regularly in our work. However, it does require caution and responsibility, which is why we are hiring recognized experts in the field.
  4. Installation of a membrane to ensure water-tightness of all infrastructures
  5. Concrete work for ventilation station
    Concrete work for all infrastructures
  6. Installation of mechanical and electrical equipment, as well as architectural finishes and exterior design
    Delivery of equipment to work site
    Installation of equipment
    Performance testing on mechanical equipment
    Construction of ventilation station’s external structure

For more information on mechanical ventilation stations, visit the page in the Major Projects section

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The project in images

This work is made possible through funding from the Ministère des Transports du Québec.

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