Construction work is officially underway on a major project at Toronto’s Union Station.

Metrolinx announced in December that piling work has begun at the station as part of the broader Union Station Enhancement Project (USEP).

The piles will form the foundation for the future south concourse that will connect customers between Bay and York Streets. Once complete, the concourse will span approximately 325 meters, or roughly the length of a 12-car GO Train.

The first of over 50 piles were installed in mid-November. The piles are constructed by driving a hollow tube into the ground, placing large steel supports into the tube, and filling it with concrete.

Piling is starting at the west end of the USEP work area and will move east as the work progresses.

Getting to this point involved a lot of preparation, Metrolinx says. As many as 14 structural steel supports had to be installed along the heritage trainshed to reinforce and protect the structure. As well, platforms 24 and 25 and 26 and 27 were demolished to make way for new, wider platforms.

Through this winter, the existing track slabs that remain from earlier in the project will be demolished, and excavation for the new south concourse will begin.

Once the required depths are reached, crews will begin constructing the concourse concrete slabs, columns, and stairs to access the new platforms.

Inside the station, two sets of temporary stairs are under construction – one in the south end of the VIA concourse, which will connect customers to the retail level below, and the other in the east end of the hallway that runs along the south side of the existing concourses, that will connect to the Scotiabank Arena area, just outside the existing entrance to the Bay concourse.

Once complete, the pedestrian walkway located south of the VIA concourse that connects to 25 York Street will close permanently as the new concourse will occupy this area.