ROTTERDAM — Schalmont school officials are disputing the estimates of cost to the district of a 15-year tax deal the Rotterdam Industrial Development Agency has made with the SI Group. Town officials stand by the deal.

District administrators claim the figures provided by the IDA don’t portray the true tax impact the SI Group’s agreement will have on Schalmont’s budget starting next year. Business Administrator Mark Kellett said the deal will create an estimated $6.36 million in lost revenues through the duration of the agreement, which is a payment in lieu of taxes, or PILOT, agreement.

“[The SI Group] got everything they could have dreamt of in a tax reduction,” he said.

In 2007, Kellett said the Niskayuna-based chemical manufacturer paid $631,805 in school taxes on its 40-acre manufacturing facility off Main Street in Rotterdam Junction. Using this figure and estimating a modest 4 percent annual increase in school tax rate, the district would have collected about $12.6 million before the PILOT agreement was implemented, he said.

“SI got just what they wanted,” he said. “They got a tax cap.”

Under the conditions of the PILOT agreement, the company will pay about $11.5 million in town, county and school taxes over 15 years, about two-thirds of which will go to Schalmont. The agreement also calls for the SI Group to make an annual $30,000 contribution to the district, for a total of $450,000 through the period.

SI also agreed to drop any litigation with Rotterdam over its property assessment and agreed to allow the town to build a water tower on company-owned land. Last month’s agreement cancels out a 13-year PILOT agreement signed in 2005, which paid Schalmont roughly $15,000 annually for improvements made to SI’s Rotterdam Junction property but not reflected in its assessment.

IDA Attorney Gerard Parisi said the district’s estimates fail to include a 2002 state Supreme Court decision that set the property value of SI’s plant at $18 million. He said the town’s outdated equalization rate coupled with last year’s revaluation improperly boosted the property to its present $31 million assessment.

“They went up to $31 million for no reason,” he said.

Parisi said a retroactive court-ordered reduction of the company’s assessment would be inevitable, meaning the district would have eventually faced repaying part of the taxes. By working out the PILOT agreement, he said, the town saved up to $150,000 in legal fees and the school won’t face the near certainty of a hefty repayment.

“It’s a falsely inflated number they’re getting now, but they’d lose that anyway,” he said.

In total, Parisi said, the PILOT agreement details will result in no additional taxes being levied on residents. Also, he said the agreement means the company will continue to pay taxes in Rotterdam, rather than moving its plant and 182 jobs elsewhere.

“There is no cost to the taxpayers,” he said. “I cant be more clear about that.”

Kellett doesn’t agree. “One of our major pieces of commercial property just got its taxes cut in half,” he said. “We don’t know what our revenues will be yet to see the result of this.”