Deep in the belly of Union Station a major construction project is underway. Workers are digging down through the floor of the basement, expanding and renovating the concourse level to handle the increased demand on the venerable old limestone giant. The miserable train shed is getting a new glass atrium (hooray for natural light) and the TTC is adding a new platform to its station.

When it's finished, subway riders will be able to saunter from the station into the new GO concourse without facing so much as a set of stairs.

One of the most precarious parts of the build is the creation of a new level below the station where there was previously only dirt. To do this, builders are literally propping up the building's existing support columns on brand new extensions.

The mammoth project is projected to cost around $715.4 million (the original budget was $640 million) and will drastically improve the quality of the busy transit hub. Workers are roughly halfway through the anticipated construction period, so here are some numbers on the project as it currently stands:

• 2.5 - The area of the dig down in football fields
• 115,400 - Square feet of space already excavated
• 193 - Support columns replaced so far
• 447 - Support columns due for reinforcement or replacement
• 45 - Truckloads of soil removed from the site daily (600-900 tonnes).
• 160,000 - Square feet of new retail space
• 300 - New jobs created
• 1,271,772 hours - Number of work hours completed so far
• 30,000 - Square metres of green roof on the new train shed
• 48 - Number of steel columns in the new glass atrium

MORE IMAGES:

Cement truck at work

Recent aerial view

Projected look of the finished extrior

Revitalized GO concourse

New moat roof

Finished retail concourse

Chris Bateman is a staff writer at blogTO. Follow him on Twitter at @chrisbateman.

Images: City of Toronto, NORR Architects