WINDSOR, Ont. — To most people, including truckers driving over the existing Ambassador Bridge, work on the new $5.7-billion Gordie Howe International Bridge 3.2 kilometers away isn’t apparent yet, because the two towers which will hold up the bridge have yet to be constructed.

But, work on the footings for those towers is well underway and tower construction itself will start by summer, bridge officials told reporters on a tour of the site in late November.

The two A-frame bridge towers – one on the Canadian side and the other on the U.S. – will be a defining feature of the cable-stayed bridge, North America’s longest with a main span at 853 meters.

“It will be the biggest in North America by far, and the fifth longest in the world,” said project lead Terry Poole of Bridging North America, the international consortium building the bridge.

The towers themselves, when finished, will be a dominant skyline feature of the Windsor-Detroit area – 220 meters (750 ft.) in height – as high as Detroit’s tallest skyscraper, the GM Renaissance Center. But the bridge’s opening date is still some time off – November, 2025.

Pre-construction work, including removing soil moisture, relocation of utilities, a service and emergency access road on the Canadian side, are largely complete.

What’s new – and perhaps for various perennial skeptics, visual proof that the bridge itself is being built – is the fact that 12 caissons or concrete shafts on the Canadian side are almost finished. Similar work on the U.S. side is also underway, and massive blue cranes can also be seen.

The caissons, or shafts, support what will be the bridge towers.

The shafts are dropped almost 30 meters into the ground – six shafts per pier cap or base for each tower leg – inserted with a more than 40-meter cylindrical rebar cage – and then filled with concrete.

Altogether, the bridge construction project is “really four in one,” said Bryce Phillips, CEO of the Windsor-Detroit Bridge Authority (WDBA), the Canadian Crown agency overseeing work. (The bridge is being built entirely by a Canadian public private partnership).

That includes the bridge itself, the two ports of entry, including Customs plazas, and the road and interchange connecting the U.S. plaza to Interstate 75, less than a mile away. Construction of the ports of entry will take place as the bridge is being erected, officials said.

Work on I-75 is expected to start within “the next few months” with reconstruction of ramps to and from Springwells St. and service drives between Springwells and Green St., a fact sheet stated.

Phillips called the work to date “impressive,” even though it may not be obvious to the public. He said construction is now “scaling up” with peak construction years slated for 2021-2023.

Locally, some 200 trucks per day will be needed to carry additional fill and aggregate to the Windsor port of entry site.