Construction of Victoria's long-awaited sewage treatment system is on time, but may not be on budget.

The team behind the $765 million project is forecasting it could cost at least $10 million more than expected.

In a report to the board overseeing construction, the project team says a hot construction market on Vancouver Island has pushed up the price of materials and labour.

Completing the project as planned could cost $30 million more than the original budget, but those cost overruns could be reduced to $10 million by dropping some aspects, the report said.

"Frankly, given the climate of construction in our region over the last few years, I would be very surprised if we had not heard something like this come forward," said Barb Desjardins, the mayor of Esquimalt and chair of a regional committee overseeing construction.

Contracts that have been awarded so far for installing the conveyance pipes have cost more than expected, whittling down contingency funds, the report said.

A pipe is installed along Dallas Road for the new sewage treatment system for the Capital Regional District. (Capital Regional District)

To keep the total cost in check, the project team is recommending eliminating three of the four remaining conveyance components. The report notes they may no longer be necessary for the success of the project.

Despite potential cost overruns, Desjardins said she is pleased with how closely expenses are being watched.

"Everything that we receive from the project board to date shows that they are being very conscious of the public purse strings," Desjardins said.

Grants from the provincial and federal governments are covering $459 million of the project cost, but any additional budget requirements would fall to local taxpayers, unless more grants are found.