The Liberal government has repeatedly said construction of the Evergreen Line connecting SkyTrain to Coquitlam Centre will be on budget - but it turns out mediation is underway with the contractor to see who will have to pay for cost overruns.

During the tunneling portion of the project from North Road down to Port Moody, there were major issues with soil conditions and groundwater. At least four major sinkholes opened up that had to be dealt with as an additional expense.

The province has always insisted this was a fixed-price contract, and construction firms would be responsible for the extra costs.

Now it turns out SNC Lavalin, the lead contractor, has been negotiating with the province to see who is actually on the hook.

"You know, on a project this complex, there are always things that come up that weren't anticipated in the early days," said Peter Fassbender, the minister responsible for TransLink. "I know those have been dealt with by the contractor and the project authority. This project will be on time and on budget."

Speaking outside Inlet Centre Station in Port Moody, Fassbender couldn't say exactly how much the cost overruns were - but he did repeatedly say the project was on time.

Trains were supposed to be running from Lougheed Town Centre to Coquitlam Centre this summer, but that has since been pushed back twice.

The Evergreen Line is now scheduled to open in early 2017.

In an email, a spokesperson for SNC Lavalin said the company does not comment on ongoing mediation or litigation.