After years of guesses and ballpark estimates, we finally have firm schedule and cost estimates for the planned Gordie Howe International Bridge.

As announced Friday morning in Windsor, the bridge will cost $5.7 billion (Canadian), or about $4.4 billion in current U.S. dollars. Of that total, about two-thirds will pay to build the bridge, the inspection plazas in Windsor and Detroit, and the interchange with I-75 in southwest Detroit.

The other third of the total cost will pay for operating and maintaining the bridge for decades to come.

The official construction schedule now predicts the bridge will open to traffic in late 2024 after a roughly six-year construction period.

Both the cost and schedule updates represent a mild sticker shock over previous estimates. But the new numbers are based on a firm fixed-price contract signed between the Windsor-Detroit Bridge Authority and Building North America, the consortium of firms selected to design, build and operate the span.

"I think it's great value for the money," Dwight Duncan, chairman of the bridge authority, told reporters at the media event in Windsor. "Early estimates were just that — early."

And, in a not-so-veiled message to the Moroun family that owns the rival Ambassador Bridge and that has fought for years to delay the Gordie Howe project, Duncan insisted that nothing could now stop the new bridge from being built.

"We will fight any attempt to slow this project down," he said. "Anybody who wants to take us on is going to face a buzz saw."

Under discussion since at least the 1990s, the planned bridge project has now reached a crucial milestone with the signing of the formal contract with the design-build team. Building North America leader Tom Middlebrook said Friday the team would hire about 350 people by the end of the year and eventually have 2,500 workers on job sites in both Windsor and Detroit.

That workforce will be split roughly evenly between Canadians and Americans under the terms of the agreement between Canada and the State of Michigan, the two governments that will jointly own the project.

Read more:

Crossing Detroit-Windsor border getting tougher

Judge dismisses Moroun attempts to block bridge

As previously announced under the Canadian-Michigan agreement, Canada will pay the entire cost upfront and be repaid with toll revenue over the coming decades. Michigan will eventually receive half the toll revenue once Canada's upfront costs are repaid.

Construction is already underway on both sides of the river on preliminary site work, but a formal celebration is scheduled for next Friday in Windsor at which leading political figures are expected to attend.

Longtime backers of the project were upbeat Friday about the signing of the formal contract agreement.

"This project will make very Canadian and every American proud," Duncan said. "It will encourage new investment in the region."

And Andy Doctoroff, Michigan Gov. Rick Snyder's point man for the project, echoed that.

"We made it," he said. "We still have a bridge and an interchange and two ports of entry to build, but if folks knew just how much went into arriving at this critical milestone and overcoming legal obstacles, the feeling is immensely gratifying."

Contact John Gallagher: 313-222-5173 or gallagher@freepress.com. Follow him on Twitter @jgallagherfreep.