North Stonington — As the vote on the proposed $40.52-million school building project nears, officials can't seem to agree on how exactly that expense would affect resident's taxes.

Selectman Bob Testa said at a Board of Selectman meeting last week that the project would mean a 4.08-mill increase, which, combined with other town obligations, would mean an overall 6-mill impact on taxes. He added, however, that the town may be able to absorb some costs, meaning the actual impact would be lower.

Testa's comments became a source of contention during an hourlong public comment period at Wednesday's Board of Finance meeting, during which he and Board of Finance Chairman Dan Spring became involved in a heated argument about the numbers.

Spring believes it's misleading for Testa to cite the cumulative mill rate impact that includes other obligations, like the new emergency services building, which is expected to raise the tax rate by 0.85 mills.

He also took issue with the 4.08-mill impact Testa cited for the project alone, saying it is too high and that the selectman might be referring to the impact from the originally proposed $47-million project. The project currently on the table would actually raise the mill rate by 2.5 to 3.5 mills, said Spring, who added that an explanation of those numbers will be available during Monday's town meeting on the subject.

Testa, however, said Spring's numbers aren't adding up.

"I have no idea where those numbers are coming from," said Testa. He said he got the 4.08 mill number from the 20-year bond schedule, which is the schedule recommended to the town by its financial advisers.

He said Spring has previously cited numbers from the 25-year schedule, which was not recommended by the financial advisers and would mean the town had to pay more in interest. But even the impact of the 25-year plan, according to Testa, is 3.69 mills.

One thing the two officials can agree on, however, is that they'd like to keep taxes as low as possible.

"I would like to think that we're going to make some reductions and we're going to minimize the impact" should the project pass, said Testa of the estimated 4.08-mill increase.

Spring said he hopes the cost of the emergency services building can be absorbed, allowing the Board of Finance to avoid raising tax rates.

k.catalfamo@theday.com