Winnipeg's city council will have to decide on Tuesday if they'll allocate more funds to Shoal Lake 40 First Nation's "Freedom Road" project.

The city has already committed $10 million to help create an all-season road out of the community that supplies Winnipeg with its drinking water.

The community itself has been under a boil water advisory for 18 years and needs the road so a water-treatment plant can be built.

In this year's budget, the city announced plans to fulfil the final $6 million of its $10 million commitment to the project.

The province and federal government had agreed to fund the remaining two-thirds of the $30 million project.

Now, the project is forecast to cost much more than originally thought – a total of $46.5 million.

The project is being overseen by the Manitoba East Side Road Authority, a group assigned by the Province of Manitoba.

Ernie Gilroy, the authority's CEO, said it's not surprising the costs spiked.

"The $30 million dollar estimate was based on a conceptual design, and you don't know until you do the soil testing what's under the soil," said Gilroy, adding the $30 million estimate is now five years old.

Gilroy said they first thought they could build on sand and that's now changed to more expensive rock fill. The estimate didn't include administrative costs either. Those are now estimated at about $2.4 million.

"You have to have engineers administering the contract and that's a pretty common value," said Gilroy.

He also said two city-constructed bridges, which were needed for the project, ended up costing more than initially forecast.

"There's two bridges the City of Winnipeg is constructing, and those bridges were originally assumed to be $1.79 million," he said. "Today they are assumed to be $4.5 million, so between the change in the sub-grade [sand vs. rock fill] contract, administration and the increase in the city's bridges, all of that comes in at $46.5 million."

Councillors Cindy Gilroy, Matt Allard, Russ Wyatt, Ross Eadie, Jason Schreyer and Shawn Dobson plan to introduce a motion on Tuesday at the budget vote to increase the commitment by an additional $5.5 million.

That would bring the city's total commitment to $15.5 million, more than 30 per cent higher than originally predicted.

"The province is prepared to commit its $15.5 million, subject to the other two parties [federal government and City of Winnipeg] contributing an equal amount. So that agreement is currently in place," said Gilroy.