Mississauga's mayor, city councillors and residents in Port Credit say they are shocked that the province now plans to demolish and replace a heritage bridge that carries six lanes of Queen Elizabeth Way traffic across the Credit River.

Built in 1934, the seven-span, open-spandrel concrete arch bridge is an example of art deco design, and was officially opened during a visit by King George VI and the Queen Mother in 1939.

The QEW/Credit River Bridge was designated as provincially significant under the Ontario Heritage Act in 2009. The Ministry of Transportation and Infrastructure Ontario had originally planned to rehabilitate the bridge, but only after a new bridge was built next to it to handle the displaced traffic.

But despite an Environmental Assessment for the plan completed in 2013 and six years of public consultations, the province earlier this month suddenly announced a new plan to demolish and replace the historic bridge.

"We were on a clear path. We sought to have the bridge rehabilitated. The plans seem to have been upended just this month," Mississauga Mayor Bonnie Crombie told CBC Toronto.

Mississauga Mayor Bonnie Crombie says the cost savings may not be worth what will be lost. (CBC)

In a public presentation, MTO and IO suggested that demolishing and replacing the bridge would be more efficient than rehabilitating it, and that constructing identical twin bridges would reduce construction duration and costs.

Rehabilitating the 85-year-old bridge "introduces additional complexity and risk — jeopardizing the overall project schedule," the presentation said.

The provincial report also says the preferred option is to replace the bridge with identical twin box girder bridges, which is a design that is common and easier to construct than an arch bridge. The report notes the bridge will lose its cultural significance, but suggested the decorative lighting standards — which date back to the bridge's commemoration — would be salvaged and reinstalled.

The Twin Box Grid replacement bridges are now the province's preferred option. (supplied)

Mayor Crombie says the cost savings may not be worth what will be lost.

"They think they're going to save a lot of money if they tear down this gem of a bridge. But you really can't put a price on this piece of heritage and history of the bridge," she said.

"Too often we tear down treasures that we later regret. And we can never replace them again. So we really need to make a concerted effort to save this piece of our history, which is really a piece of our identity."

Mississauga city council unanimously passed a resolution this week strongly objecting to the proposed demolition and asking that the mayor send a letter of strong objection to Premier Doug Ford and local MPPs.

Crombie says from her understanding the bridge has been rehabilitated a number of times over the years and can be again.

Rudy Cuzzetto, the Progressive Conservative MPP who represents the riding of Mississauga-Lakeshore, says after 85 years, the QEW Credit River Bridge has reached the end of its useful life. Either replacement or extensive reconstruction is needed to ensure public safety. (supplied)

"[It] had a 75-year lifespan five years ago when they made the assessment, so there's at least 70 more years of lifespan in that bridge," she said.

But Rudy Cuzzetto, the Progressive Conservative MPP who represents the riding of Mississauga-Lakeshore, says that's not the case.

"It's not true that the bridge is rated A-OK for 75 years. After 85 years, it has reached the end of its useful life, and it often requires emergency repairs and lane closures.

"Either replacement or extensive reconstruction is needed to ensure public safety," said Cuzzetto in a statement to CBC Toronto, adding as many as 200,000 vehicles travel the busy stretch of highway that connects Hamilton, Burlington and Oakville to Toronto each day.

Cuzzetto says the proposal to demolish the bridge is not yet approved, and there will be a consultation period, beginning next March, as part of the environmental assessment process.

"We are a government that listens. Our final decision will be based on the evidence and on the feedback we receive as part of this open and transparent process."

Dorothy Tomiuk, Vice President of the Town of Port Credit Association (TOPCA) wants to know what, after hearing from the community and committing to a plan, caused the sudden decision to demolish the bridge. (supplied)

But Dorothy Tomiuk, Vice President of the Town of Port Credit Association (TOPCA) says her group has been a stakeholder in the consultation process since 2012.

"[We've] been involved in every session, every workshop, every public information centre led by the Ministry of Transportation that led to the final design," she said.

Tomiuk wants to know what, after hearing from the community and committing to a plan, caused the sudden decision to demolish the bridge.

"If they have suddenly done a study and discovered that engineers feel the bridge is dangerous, then I would say, 'My goodness, why are you concealing this?'" said Tomiuk. "All of the traffic that goes over that bridge daily? I think everyone should be informed of what the danger is and how long the bridge has. Let's see the engineering report immediately."

Tomiuk also said the bridge's heritage designation would have to be rescinded by Lisa MacLeod, Ontario's Minister of Heritage, Sport, Tourism, and Culture Industries.

"But the real issue is why are they demolishing the heritage bridge at all when it's obviously faster and intuitively cheaper to simply rehabilitate the existing bridge and carry on?"