With just a day before the referendum on Regina's sewage plant upgrade, two important groups on opposing sides aren't saying how much they're spending on the campaigns.

The Canadian Union of Public Employees (CUPE) supports the "Vote Yes" campaign, and has been providing an unknown amount of money to Regina Water Watch, the group that started the anti-P3 petition that led to a referendum being called.

Regina Water Watch spokesman Jim Holmes told a meeting earlier this month he "had no idea" how much money CUPE had contributed to the "Yes" campaign.

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Regina is holding a referendum Sept. 25 about a $224 million sewage plant upgrade. (CBC)

Among the things that have received CUPE support is the ReginaWaterWatch.ca website, which had its domain name registered by the union.

The Regina Chamber of Commerce, meanwhile, is in favour of the "public-private partnership" on the $224 million project and supports the "No" side. The Chamber has placed a number of newspaper ads and many of the "No" signs displayed on lawns have its name on them.

Neither group is disclosing exactly how much money they've spent.

When CBC News asked Tom Graham, who is the general vice-president of CUPE Saskatchewan, about financial support for the "Yes" side, he replied: 

"We are just not prepared to release anything right now. We just think it's going to cloud the issue."

Graham would only say that CUPE is spending less on its campaign than the City of Regina is on its $340,000 "vote no" campaign.

He said he would be willing to reveal the dollar figure after the referendum, on Sept. 27, but not before.

A spokesman for the Chamber, executive director John Hopkins, told CBC News that since CUPE won't talk, it won't release how much it's spending, either.

The City of Regina also budgeted for a non-partisan public information plan about how, when and where people can vote — including print, radio and social media — that was expected to cost $100,000 to $120,000.

Check out the referendum question:

That the Council of the City of Regina publicly finance, operate and maintain the new wastewater treatment plant for Regina through a traditional Design, Bid, Build (DBB) approach.

Click a choice to see what it means:

YES
NO

If you vote Yes:

• you support the proposal to use a traditional project approach for upgrading the wastewater treatment plant.

• you reject the P3 approach.

This is the choice that Regina Water Watch encourages.

If you vote No:

• you reject the proposal to use a traditional project approach for upgrading the wastewater treatment plant.

• you support the P3 approach.

This is the choice that the City of Regina encourages.