Saint-Grégoire mechanical ventilation station

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 early 2024

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

Métro impacts: No

Bus impacts: No

Impact on local residents

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Worksite update - October 2023

Paving and landscaping
We have started work around the building, including rebuilding the sidewalks and paving the street. The trailers have been moved out of the way. Next spring, we will landscape a small grassy area near the new building, where three park benches will be installed.

Building exterior
There is still concrete work to be done on the building. Once that is complete, we will cover the walls and move onto finishing work. The worksite is scheduled to close in early 2024.

Building interior
We are finalizing the building’s interior and finishing the installation, testing and commissioning of equipment.

We have installed massive high-performance noise suppressors to dampen the sound of the underground fans. Once the ventilation station is operational, the noise it emits will comply with municipal by-laws. The noise level outside the building will not exceed 50 decibels, even when the ventilation station is operating at full capacity, which is unusual. The station’s noise level will be comparable to that of a household dishwasher. In fact, it will be so low that normal conversation or ambient noise could easily cover it.


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

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.

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.

New work phase starting

The bedrock excavation is complete. We are now starting a new work phase consisting of reinforcement installation, formwork and concrete pouring. This will not require any loud machinery nor cause any vibrations, but you will see concrete mixers present on site.

Concrete pouring

Once we start pouring a batch of concrete, we cannot stop and continue the next day. All the required concrete needs to be poured at once to ensure that the structure being built is up to code.

As such, some particularly long pouring sessions may have to continue past 7 p.m. This does not apply to all upcoming pouring sessions, only to those involving particularly large amounts of concrete. We will only work past 7 p.m. in exceptional situations.

Excavation ending soon

Our last batch of micro-blasting was completed in late January, and we are now done with that stage of the excavation. We are currently digging out the lateral portion of the tunnel. This part will be done entirely by mechanical means, using a rock breaker and, occasionally, a jackhammer. We expect to finish all excavation work for this project by mid-March 2022 at the latest, putting us one month ahead of our initially planned schedule. This means that the noise from the rock-breaking equipment will stop some time in the next few weeks.

Next steps

Once the excavation is done, we will move on to protecting the facilities from underground runoff water. We will install a waterproofing membrane and an underground water drainage system. Next, we will start building the structure, including reinforcement and concrete work. This will be relatively quiet, and the equipment used will not cause excessive noise or any vibrations.

Last week, we reached the end of the tunnel, which completed our micro-blasting work for this year. Please note that a portion of the tunnel has yet to be excavated and that we will do so after the holidays. In early January, we will decide which method to use to excavate the remaining part of the tunnel. This step could be carried out using either micro-blasting or mechanical equipment.

Concrete spraying

After the holidays, we will begin concrete spraying. We wish to inform you that some of this work will be carried out in the evening and early at night. More specifically, we will perform work inside the tunnel from January 3 to 14, 2022, Monday to Friday, between 7 p.m. and midnight.

We are aware of the inconvenience this work may cause to you, and we will put in place measures to reduce the noise:

We will not use equipment and machinery outdoors.

We will install a temporary roof, made of plywood and covered in insulation, over the shafts that lead to the tunnel.

We have implemented measures to reduce the noise, and we believe that any work heard will be very limited around the worksite.

Work at the mechanical ventilation station site is well under way. We are still excavating the tunnel and we have already extracted 60% of the total volume of rock to excavate. We will finish micro-blasting earlier than expected, which was the spring of 2022. If we keep up the pace, we could finish this step in December 2021.

The noise level should remain the same until we complete this part of the project. Please be assured that we will continue to monitor noise levels to comply with the authorized limit at all times and control the dust from the worksite.

Saturday work

We may occasionally work on Saturdays over the next few weeks. This work, generally to build the tunnel or excavate, could take place between 10 a.m. and 6 p.m.

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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