Here's how Toronto's new elevated subway stretch is being built

The new Ontario Line subway will include a rare (for Toronto) stretch of elevated track for its northeastern leg through the Thorncliffe Park area, and work is already in full swing to construct the above-grade portion of the new 15.6-kilometre transit line.

The line's Don Valley Station (renamed from Science Centre after the provincial government unceremoniously shuttered the landmark science museum in June 2024), along with Thorncliffe Park and Flemingdon Park stations, will be built above street-level and served by an elevated guideway.

Construction activity is now setting the stage for these new stations, as well as the elevated corridor that will carry trains across the terminal stretch of the route.

The elevated corridor is being constructed along the east side of Don Mills Rd.

Preparations for ongoing construction include the October opening of a temporary bus terminal at Don Valley Station, and the November completion of watermain relocation work along Don Mills Rd.

Among the many ongoing tasks laying the groundwork for the Ontario Line's northeastern leg, crews are in the process of pile drilling and building pier foundations for the elevated guideway on the east side of Don Mills Rd. between Eglinton Ave. and Wynford Dr.

The four-month task has already seen the drilling of multiple piers (numbered D39 to D41 in Metrolinx documents), with work still ongoing on the remaining piers in this work area (numbered D36 to D38).

Location of piers for elevated guideway

The next phase of pile drilling and building pier foundations for the guideway, covering the east side of Don Mills Rd., just north of Wynford Dr., is scheduled to commence in Feb. 2026.

Diagram of the supporting columns for the elevated guideway.

Columns supporting the elevated guideway will soon line a corridor running north/south just east of Don Mills Rd., providing structural support for the guideway and adding a permanent visual change to the neighbourhood.

Each pile foundation will be 1.8 metres in diameter and will take between 15 and 19 days to complete.

Other ongoing tasks along this stretch include substructure work, building pier columns and pile caps for the elevated guideway, slated for completion in mid-January, and secant piling (a type of retaining wall used to brace soil and reduce water in an excavation) for the foundations of station basement walls for the future Don Valley Station, ongoing until late January.

Secant piling diagram

Don Valley Station will be the northern terminus of the line, connecting with the Line 5 Eglinton (Crosstown LRT), should Metrolinx ever decide to open the beleaguered transit line.

Unlike other more intensive tasks for the Ontario Line, which require 24-hour construction, the piling work being carried out for the elevated stretch of the line only requires shifts on weekdays from 7 a.m. to 7 p.m. with periodic evening and weekend work.

Over at the future site of Flemingdon Park Station, crews are still in the earliest stages, including setting up site offices and marking work areas. 

Tree removal near E.T. Seton Park Archery Range will follow in late December or early January, while work in the new year will include installation of light poles, pile foundation drilling, and other tasks to prep the station site.