A contractor's mistake means a freshly poured section of concrete on the Dundas Place project will have to be ripped up and removed, city officials say.

Contractors working on Dundas Street east of Clarence Street were busy on Friday cutting and removing concrete sections poured less than 10 days ago. The concrete being removed is in the middle section of the Dundas Street, which is in the final phase of a two-year, $16-million renovation.

Jim Yanchula, the city's manager of downtown projects, told CBC News the concrete was poured to "an insufficient thickness" and will have to be re-done.

"It didn't meet our contract specifications," he said.

Yanchula said the concrete acts as a "sub-floor" and supports the brick paver stones that will form the surface of the revamped street.

It's the central section of the street that will be the driving surface for vehicles.

The concrete had to be removed," he said. "It was an insufficient depth and wouldn't hold the bricks. I'm just glad we caught it now during our normal inspections."

The 65-metre segment of concrete that will need to be redone is located in the middle section of the street, just east of the Clarence intersection. Recently poured sidewalk sections in that area of Dundas won't need to be re-poured, he said.

Yanchula said the error was caught by a construction consultant under contract with the city. A representative of general contractor Amico Infrastructures Inc. declined to comment when contacted by CBC News.

Yanchula said Amico will have to cover the cost of removing and re-pouring the concrete.

"It's not a city expense," he said.

He said Amico has re-assigned crews to work on other sections of the street while the concrete is removed and re-poured.

The city has said the project to resurface Dundas from Richmond to Clarence will be complete before the end of the construction season at the end of the fall.

"The wild card isn't this, it's more the weather," said Yanchula. "Right now ... we didn't see anything today that affects the schedule. We're still on target for the end of fall."

The project to revamp Dundas includes extensive work to replace plumbing and other services beneath the road surface. Adding the decorative pavers and eliminating curbs are part of a plan to transform Dundas into a "flex street" that can be pedestrianized for special events.

The section of Dundas from Ridout Street to Richmond Street was the first of the project's two stages and concluded up last year.