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Eglinton Crosstown West Extension

Eglinton Crosstown West Extension - Construction

Building a subway in developed neighbourhoods across a large and busy city is a complex design and engineering undertaking. Here is some general information from other projects to help you understand what teams are considering while they develop more detailed plans for delivering the Eglinton Crosstown West Extension.

How is a subway tunnel constructed?

Although the alignment will evolve throughout the detailed design process, the Eglinton Crosstown West Extension will use a mix of below-grade (tunnelled), at-grade (ground level) and above-grade (elevated) structures. Subway tunnels can be constructed using: tunnel boring, cut-and-cover and mining construction techniques.

Tunnel boring involves the use of a tunnel boring machine (TBM) for the tunnelling excavation process. As the tunnelling progresses, the excavated material is brought to the TBM site through the tunnel using bins mounted on rail cars or a conveyor system.

Cut-and-cover is used for shallow tunnels where a trench is excavated and then an overhead support system strong enough to carry the load of what is to be built above the tunnel is installed. Using the sequential excavation method, a ‘roadheader’ mines the tunnel in sections and a support canopy is installed simultaneously to keep the ground stable.

Once tunnelling between the stations is complete, the tunnel surfaces are finished and the tracks and electrical services are installed.

Tunnel Boring Machines

The tunnel boring machines (TBMs) will operate up to 35 metres underground, 24 hours a day, seven days week, and travel approximately 10 metres per day.

Photo of the Crosstown LRT tunnel boring machines
Crosstown LRT tunnel boring machines

TBMs move forward with the help of precast segment tunnel liners that are placed on the tunnel walls as it drives through. The TBMs propel themselves forward by pushing against the liners.

Crosstown LRT precast tunnel liners
Crosstown LRT precast tunnel liners

For the portion of elevated track across the Humber River, a bridge must be built to minimize impacts on sensitive environmental areas below. To stand upright, bridges must balance forces of tension and compression, while carrying the load of the subway and resisting environmental forces. Tension is a pulling force. Compression is a pushing force. Bridges channel the forces into chords or horizontal segments and piers or towers.

First, a foundation is set into the ground for piers to be built upon. Then, towers are built upward from the base, complete with a support system to connect the towers, cables and abutments (ends of the bridge). Sections called ‘superstructures’ are then built from end to end at even intervals and secured to the support system. To complete the bridge, the deck/track surface is assembled and furnished with electrical and lighting systems. When all elements are complete, the bridge undergoes final testing to ensure it meets quality standards before operation.

Bridge construction is part of the stations, rail and systems work that is expected to begin in 2025-2026.

Photo of a bridge over the Humber River

Elevated Guideway: West of Scarlett Rd. to east of Jane St.

The elevated guideway, between the Scarlett and Jane portals, is approximately 1.5 kilometres long. Stations at Scarlett and Jane are anticipated to be elevated stations along the guideway.

The construction of elevated station platforms will be very similar to the elevated guideway. However, the station structure will be wider than the guideway to accommodate the needed passenger space and will also have a larger at-grade footprint to function as station entrances.

A new bridge across the Humber River east of Scarlett Road will be constructed as part of the elevated guideway. Construction of the new bridge will involve:

  • Building foundations for piers
  • Constructing piers
  • Building and placing bridge sections
  • Installing systems and track

This construction is part of the stations, rail and systems work expected to begin in 2025-2026.

Stations are designed considering the future customer needs and local neighbourhood environment. Metrolinx considers things like safety, accessibility, access to other transportation and transit, ridership and passenger experience.

Constructing a station is a multi-step process.

Rending of Caledonia Station
Caledonia Station on Eglinton Crosstown rendering

Preparing an underground site for station construction typically begins by protecting or relocating any underground utilities such as power lines, water lines, sewers, gas pipes, cable/telephone lines and storm drains. If the station is being built under a street, a temporary concrete decking is installed once the area is excavated to establish a temporary street surface during construction. The next step is continued excavation and installation of shoring along the edges of the excavation for support.

Once the foundation is complete, construction of the inside of the station begins.

Rendering of Burquitlam station
Burquitlam station is an attractive part of Vancouver’s Evergreen Line. (Photo by Andrew Latreille, courtesy of Perkins & Will)

Above and underground stations feature similar elements in the public areas like architectural design treatments and artwork, information displays, lighting, signage, security monitoring devices and many other design elements. At-grade stations are generally less expensive and quicker to construct because less time is spent excavating soil, meaning building can begin and end sooner than tunnelled stations.

Headwalls

  • Headwalls are constructed to support the tunnel at the site of the future underground stations and emergency exit buildings.
  • Headwalls for stations at Royal York, Islington, and Martin Grove will be constructed with secant piles, which are overlapping columns made from poured concrete reinforced with steel. This method involves drilling.
  • Headwalls for the station at Kipling will be formed with jet grout, which is a type of concrete that is pumped into the ground from a temporary grout plant onsite. Using this method will reduce impacts by avoiding utility relocation because drilling is not required.
  • Two emergency exit buildings near Islington and Royal York also require headwalls.

Photo of headwalls
Photo of headwalls

  • Before we start digging to build the tunnel, we must first consider the infrastructure that is already in place. We do this work before everything else in order to protect the utilities and services that the community relies on every day.
  • The proposed tunnel alignment significantly reduces impacts to existing infrastructure by moving around utilities wherever possible. However, we will need to remove, replace and relocate some utilities.
  • The number of utilities will vary by location but the work will include protecting hydro, water, sewage, telecommunications lines, traffic lights and street lighting in order to build the project.
  • Utility work is expected to begin along the corridor in spring 2021. We will be sharing more information for public feedback as it is available.

Photo showing utility work
There are many complexities when utilities overlap a project corridor - each line that runs parallel to the road is a separate utility that will require its own coordination.

Traffic & Transportation

During the advance tunnel contract temporary impacts to traffic flow along Eglinton Avenue is expected in stages during construction. A detailed traffic plan will be shared for public feedback before construction starts.

Potential Impacts

  • Temporary partial road and lane closures and turn restrictions
  • Temporary impacts to pedestrian and cycling routes
  • Temporary impacts to existing bus stops

Potential Mitigation Measures

We are working with our municipal partners to develop a construction traffic management plan which will maintain as many lanes as possible at all times and limit turn restrictions.

  • When temporary closures are required to pedestrians and cyclists, we will provide safe and accessible detour routes.
  • We will maintain access to existing transit services by temporarily re-locating bus stops as required.

Aerial photo of intersection of Kipling Ave and Eglinton Ave West.

Spotlight Case:
During the advance tunnel contract the station headwalls will be constructed in the right of way requiring a traffic management plan. The future station entrance building will be constructed on the north-west corner as well as an emergency exit stairwell at the west end of the platform during the stations rail and systems work.

Eglinton Avenue Access at Richview Residential Complex

Potential Impacts

  • The driveway on Eglinton Avenue serves as a secondary access for residents. There may be temporary restrictions during the advance tunnel contract for construction of the extraction shaft. The primary access driveways will be available from Richview Road.
  • Early designs for the stations, rail and systems work, which is expected to begin in 2025-2026, indicate further potential impacts to this driveway in order to make room for the tunnel portal and elevated guideway. The possibilities include a partial or full closure.
  • An additional traffic study will be done as the structural design of the portal and the elevated guideway continues.

Potential Mitigation Measures

  • As design of the stations, rail and systems work progresses, specific impacts emerging will be the subject of a future engagement.

Map of the tunnel port near the Richview Residential Complex

Potential temporary impacts during the advance tunnel contract and potential partial or full closure during the stations, rail and systems contract are under review and will be shared as the design progresses.

For more information please see the current Traffic Impact Assessment.

Cultural Heritage

The Cultural Heritage Report, found in Appendix G of the Environmental Project Report Addendum, identifies the built heritage resources and cultural heritage landscapes within the project area to assess potential impacts and protection measures.

We are working closely with the City of Toronto as the design progresses and will consult with the community at future engagements.

In one known instance, during the advance tunnel contract headwall construction for Royal York Station, there is potential for minor impacts to the landscape on the southern portion of the Mary Reid House property at 4200 Eglinton Avenue West.

Analysis continues and we will be sharing more information for public feedback as it is available.

Photo showing the front of the Mary Reid House and stone wall

The Royal York-Eglinton Station is being constructed within the property parcel. There will be no direct impacts to the Mary Reid House building itself; however, the construction of the underground station may potentially cause minor direct and indirect impacts to landscape features including the stone wall.

Natural Heritage - Trees and Vegetation

Metrolinx will reduce tree and vegetation removal where possible and recognizes the importance of natural vegetation along Eglinton Avenue. A tree inventory and arborist report are underway now.

  • A tree inventory documents information (i.e. measurements, species, location) on trees within the study area.
  • An arborist report documents further information such as tree health, and recommended methods to preserve trees during construction.
  • The reports will inform future public engagements.

Analysis is ongoing for tree and vegetation loss during the construction of stations, elevated guideway, traction power stations and other components of the project that will be built during the stations, rail and systems work.

For more information, please see Appendix B in the Environmental Project Report Addendum.

Photo of a pedestrian bridge
Pedestrian Bridge

Tree and vegetation loss is anticipated in some areas during the advance tunnel work. Known areas include the launch shaft/portal at Renforth Drive, headwall construction areas, and during the reconstruction of the access ramp for the pedestrian bridge west of Scarlett Road. A full review of impacts and protection plans will be shared ahead of construction. We continue to work with our municipal partners and the Toronto Region Conservation Authority.

Natural Heritage – Humber River

As noted in the Natural Heritage Report, Appendix B of the Environmental Project Report Addendum), the bridge over the Humber River will be designed to minimize impacts by avoiding in-water works as much as possible. This bridge will be constructed during the stations, rail and systems work.

As for areas and greenspace immediately surrounding the Humber River, impacts to vegetation will also be minimized as much as possible. Metrolinx will continue to work with the Toronto Region Conservation Authority as the design progresses.

To assess any potential impacts to water quality in receiving waterbodies, such as the Humber River, a floodplain impact assessment will be conducted in the next design phase when more details on pier arrangement are available. This assessment will follow TRCA guidelines and will assist with evaluating potential impacts from the new bridge, such as impacts from any increase in erosion and sediment processes due to construction.

Photo showing the Humber River
Humber River

An overall storm water quality and quantity control strategy will be developed. Potential impacts and associated mitigation measures for the Humber River will be identified as the design progresses and part of a future engagement.

Noise & Vibration

We know construction brings noise and vibration, and Metrolinx is committed to minimizing and managing these impacts as much as possible. Key elements of our approach include:

Before construction starts

  • Establish a comprehensive engagement plan to inform affected parties about the project’s scope, schedule, noise and vibration management strategies, and communication and complaint resolution protocols.
  • Develop a detailed plan to meet noise and vibration exposure limits.
  • Implement all necessary noise and vibration mitigation measures.

During construction

  • Meet noise and vibration exposure limits.
  • If exposure limits cannot be met with all practical best practices and source/ path mitigation measures, investigate receptor-based mitigation.
  • Provide advance notice of impacts and address public complaints in a timely manner.
  • Based on current assessment results, construction noise is predicted to be within the baseline background noise levels and therefore at this time, no mitigation is anticipated.

We know that noise is one of the most frequent complaints about transit service operations, and it’s particularly relevant to residences closest to the service and infrastructure.

  • The noise anticipated from operation of the project is also predicted to be within the criteria when operational noise mitigation is applied, which can include ballast mats, optimal maintenance, and timely monitoring and inspections of tracks.

For more information please see Appendix D in the Environmental Project Report Addendum.