The City of Regina says the new sewage treatment plan will cost $43.5 million less than originally expected.
The construction costs were pegged at $224.5 million. On Friday, the city said it will be built for $181 million.
EPCOR Water Prairies Inc. has been selected as the company that will build and run the facility for 30 years.
The city says it needs the upgrade to meet the demands of a growing population as well as to meet tougher federal environmental rules.
The so-called P3 [public-private partnership] aspect of the project has been controversial, with some critics saying the city is making a mistake handing over sewage treatment to the private sector.
But city officials say it's cheaper this way and Regina City Council will still have the power to set sewage rates.
A referendum was held on whether to go with the P3 model or a more traditional model, and the P3 side won.
The city says the new sewage plant on the west edge of the city will be "substantially complete" by Dec. 31, 2016.