Anyone who has crossed over the Humber River Bridge at Toronto's Islington and Finch intersection over the past few months may have noticed construction equipment and crews littered about, part of a massive undertaking to raise the bridge as traffic continues to flow.

It's all happening as part of the Finch West LRT's construction, Metrolinx upgrading and widening the bridge to accommodate the new line's tracks.

Mosaic, the constructor for the Finch West LRT project, has been undertaking the delicate task of raising the bridge. And while the crossing is only being elevated by a mere six millimetres — a little more than the width of three strands of uncooked spaghetti — the need to keep cars, buses, cyclists, and pedestrians moving throughout adds a whole other level of complexity.

Since January, crews have been using a unique construction method called bridge jacking to elevate the still-active bridge, which allows the structure to be raised carefully without threatening its structural integrity.

Existing concrete girders supporting the bridge are being lifted in increments, using a network of 18 hydraulic jacks powered by hydro pressure and electricity directed from nearby control panels to support the bridge's load in the interim.

Equipment powering the lift on the underside of the bridge.

These jacks can safely support loads in the hundreds of tons, allowing cars to use the propped-up bridge as its supporting girders are extended below. Individual girders are refurbished one by one, with 60 in total being worked on.

This includes the speedy replacement of bridge bearings, which carry loads or movement of the structure down into the bridge piers and abutments, the replacements featuring a combination of rubber and metal for improved strength.

Most will notice the construction, but few will realize the bridge is actually higher than it used to be.

Tommy Medeiros, superintendent of construction, civil and utilities, says "That is what most people don't know and can't even see. When people hear that a bridge is being raised, they usually think it's much higher, but this is more like trying to slide a piece of paper under a laptop."

Work on the bridge raising has been ongoing since mid-January and is estimated to be complete by the end of March.