An independent study of Toronto’s Gardiner Expressway says the elevated highway’s deteriorating concrete poses a significant safety hazard and that city officials must do more to maintain it, says a prominent Toronto councillor.

Several chunks of concrete have fallen from the Gardiner's underbelly in the past year. The problem is that water seeps into the highway's concrete exterior.

The water in the structure can cause steel supports to rust, and it also expands with freezing, weakening the concrete and causing it to fall away.

City engineers have been inspecting the highway and chipping away at any loose bits they find.

But according the report, these visual inspections aren’t enough to ensure the safety of pedestrians and drivers at street level, Coun. Denzil Minnan-Wong, the chair of Toronto council's public works and infrastructure committee.

Engineering firm IBI used sound wave technology to pinpoint problematic areas, including six areas of the Gardiner that city crews had deemed safe, he said.

Minnan-Wong said the report was submitted to city staff in September.

“This was identified as an issue earlier on in the year because we were uncomfortable that we were doing enough, we commissioned this peer review and this in fact confirmed our suspicions that we need to do more work.”

Minnan-Wong said an additional $20 million in capital spending will be requested by city staff to pay for better investigation techniques and repairs on the Gardiner.

Ford wants private sector to help build new highway

Coun. Doug Ford said he would support a public-private partnership to create a toll highway that runs parallel to the Gardiner Expressway, giving drivers the option of paying to drive on a less congested route.

"I’d pay the $5 to get downtown every day," Ford told reporters Friday. "But you also have to have an option for drivers not to have to go on the toll roads. I’d put a toll road separate, so there’s an option: You either get a freebie or you get a toll.”

Ford also said the city would look to senior levels of government for any help available, but said for now the city-owned road is Toronto's problem to solve.

"That’s our road and we have to take the responsibility for it," he said. "I drive on it every day."

The independent report points out – and Minnan-Wong agrees – it's impossible to eliminate the risk of falling concrete because the highway is more than 50 years old.

With files from CBC's Trevor Dunn and Jamie Strashin