Preparing for Major Construction
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- Preparing for Major Construction
Here's what to expect
While construction work is typically the most noticeable part of building a new transit line, there's a whole series of essential steps that bridge the gap between the planning and design phases of a project and breaking ground. It takes a lot of preparation to make sure everything runs smoothly from day one.
The information below provides a general overview of the processes involved in preparing for construction.
It’s important to note that methods and approaches can vary depending on the unique considerations of a project. Whether it’s an underground station, elevated guideway, bridge or new tracks, the general principles apply, but each project may require specific adaptations.
This page is meant to serve as a starting point for further exploration and help you better understand the foundational steps that set the stage for all the vital pieces of transit infrastructure Metrolinx is building.
Surveying
Surveying helps design teams understand the exact shape, boundaries, and features of a future construction site so that everything can be planned accurately and positioned correctly. The process involves mapping out the terrain using specialized tools like laser levels and GPS equipment to get very precise measurements.
Equipment like this surveying prism is used to accurately and precisely measure distances.
The data collected through surveying helps guide the entire construction process and helps make sure that the site is properly laid out and ready for the next stages of a project.
Archaeological investigations
This step is about preserving the past while building new transit for the future. Archaeological investigations involve assessing a site to see if there are any artifacts or remnants from the past that should be documented and preserved.
Archaeologists helped unearth history in Toronto’s Moss Park community through work for the Ontario Line.
After reviewing historical records and consulting with Indigenous communities to learn more about the cultural significance of an area, Metrolinx will conduct archaeological surveys and sometimes dig small test pits to check for buried artifacts. In some cases, Indigenous community representatives may be involved as cultural monitors to make sure any discoveries are handled in accordance with Indigenous traditions and protocols.
If something of interest is found, the area is carefully excavated using specialized tools and any important items are protected and catalogued.
Work on the Union Station Enhancement Project has revealed several interesting discoveries from the mid-19th century.
Geotechnical investigations
It’s important to have a strong understanding of the ground conditions where construction will take place. Geotechnical investigations involve drilling holes into the ground – commonly referred to as ‘boreholes’ – to collect samples of the earth. The samples provide important data on soil, rock, groundwater and other underground conditions that inform designs and construction plans for new transit.
A borehole drilling crew at work.
To collect a sample, a machine drills into the ground to create a borehole.
Once the drill reaches the desired depth, the head of the drill is replaced with a hollow cylinder that is pushed into the ground to take a sample of the earth that is then analyzed to determine the composition and stability of the soil in the area.
Experts also test the density and moisture content of the soil, and they determine the flow and pressure of groundwater.
A soil sample ready to be sent for analysis.
The findings from these ground investigations inform the design, construction methods and materials that will be used for the new transit infrastructure to make sure it is built and operated safely and reliably.
Geotechnical investigations typically happen before construction begins as part of the planning and design phases for a project, but they can also take place at other times during construction to gather more information and adjust work plans, if necessary.
Dive deeper into the history of borehole drilling with this story featuring the future Ontario Line.
Utility relocations
In built-up urban environments, utilities such as water, gas, electricity and telecommunications lines are often located where future transit infrastructure will be constructed. These utilities must be relocated or protected before excavation begins to prevent service disruptions and make sure construction can move forward safely and efficiently.
Relocating underground utilities is an important step to get ready for construction of new transit.
Before work begins, existing maps and records are reviewed to form an initial understanding of where any utilities should be. For underground utilities, sometimes it's necessary to follow up with further investigations to identify and map their precise location.
One common method involves using a hydrovac truck, which uses pressurized water and a high-powered vacuum to safely expose underground utilities. Once they’ve been located, the positions are marked on the ground with colored flags or spray paint markings, and the data is fed into updated maps.
Hydrovac trucks are a familiar sight at work sites where teams need to look below the surface.
Metrolinx works closely with utility providers and municipal partners to plan and coordinate the relocation of utilities.
For underground utilities, the area is excavated to accommodate planned work. For utilities on the surface or overhead, like hydro poles, structures may need to be relocated or replaced. Specialized crews are brought in to move each utility, and all efforts are made to maintain service and minimize impacts for customers.
Site mobilization
Mobilization refers to the process of transporting and setting up all the necessary equipment, machinery, and materials on the construction site. At this stage, safety measures like temporary fencing, hoarding, barricades and signage are installed to keep everyone safe as work moves forward. Mobilization is an important part of the transition from the planning and design phases of a project to being in the full swing of construction.
The careful planning and coordination involved in mobilization helps make sure everything is organized and ready for construction to proceed safely and smoothly.
Mobilization sets the stage for the entire construction process.
Grading
Grading involves shaping the surface of the ground to prepare for excavation and construction. This important step helps create proper drainage – making sure that water flows away from a construction site rather than pooling within it. By carefully leveling or sloping the ground, water can be guided where it needs to go. This not only prevents flooding but also creates a solid, stable base for new transit infrastructure.
An excavator works to shape the ground at the site of a future transit tunnel portal.
After vegetation, debris and any existing structures are removed from a site, machines like bulldozers and excavators are brought in to push, pull, and level the ground to get the site into the general shape it needs to be in for the more precise work that follows. This might mean creating slopes to guide water away, carving out terraces for different levels or levelling out uneven ground.
The next step is to carefully smooth out and level the site using smaller equipment, like graders and compactors, to exactly match construction plans. Grading makes sure the groundwork is stable and secure and sets up a project for success as construction moves forward.
Managing impacts
Building a new transit line involves heavy machinery, digging deep into the ground, and moving tons of material. All that work brings a lot of activity to local neighbourhoods and streets, and we understand that it can be disruptive for the communities we serve.
Streets may be busier, noise and vibrations may be noticeable, and everyday routines might shift temporarily. We understand that this can be challenging, and we appreciate your patience as we work to bring much-needed improvements to the transit network that will make travel throughout the region faster, more sustainable, and more convenient for everyone.
Construction hoarding signage at an Ontario Line site helps keep the community informed about ongoing work.
Metrolinx works closely with our contractors to minimize disruptions while our teams work to deliver new transit. No matter what the project, we engage with communities to address potential issues and we strive to reduce and manage impacts whenever possible through a wide array of measures, including:
- Early and ongoing communication: We communicate with communities about what to expect well in advance of any work beginning. We deliver this information in several ways, including notices, community meetings, e-newsletters, and regular updates through our online and social media channels. As work progresses, we continue to share timely information to make sure communities stay informed about progress and next steps. To stay connected, you can explore and sign up to our regional and project-specific e-newsletters on our subscription page. If you have questions or concerns, don't hesitate to reach out directly to our Community Engagement teams — we're here for you!
- Noise and vibration control: Before work begins, we make detailed plans to manage construction noise and vibration. Whenever possible, noisier activities are scheduled during daytime hours to reduce disturbances when people are more likely to be home. Metrolinx monitors noise levels on project work sites using industry-standard methods and we strive to keep them within the recommended guideline levels, which can vary depending on the project. We also listen closely to community feedback so that we can take steps when possible to reduce disruptions while we deliver important transit improvements.
- Dust and air quality management: We monitor air quality during construction and take action, if necessary, to control dust from machinery and vehicles. This can include spraying water on dusty areas or installing mesh netting on temporary fencing to reduce dust drift.
- Traffic management: Traffic management plans are put in place to safely direct vehicles, cyclists, and pedestrians around work sites. These plans can include clear signage, temporary traffic signals, traffic flaggers, and paid duty officers. Whenever possible, deliveries and the movement of equipment and materials are scheduled during off-peak hours to minimize traffic disruption.
- Site maintenance and restoration: We make sure that work sites are kept tidy and well-organized, with equipment securely stored when not in use. To help reduce dirt or mud getting tracked out onto nearby streets, we regularly water down vehicles and machinery whenever necessary. After work is completed, we work with property owners to restore affected areas, which may include replanting trees and vegetation (Metrolinx always plants more than are removed), repairing driveways, and restoring landscaping to its original condition.
- Utility service coordination: If a utility service needs to be temporarily disconnected to accommodate work on a project, customers are notified in advance by their utility provider and every effort is made to complete the work quickly and minimize disruption. In some cases, temporary solutions like backup generators are used to maintain essential services.
At every stage of our projects, Metrolinx is committed to working with communities and managing impacts while we deliver much-needed new transit for the region.
Work is carefully planned and coordinated to reduce disruptions and keep the region moving smoothly during construction.
Get in touch
If you have questions about work on a Metrolinx project being built close to you, please reach out to the Community Engagement team in your area:
