HAMPDEN, Maine — Residents of Hampden, Winterport and Newburgh got their final chance on Tuesday to ask questions and address concerns before next week’s vote to approve or deny a $51 million school construction project.

A group of about 50 people listened intently inside the current Hampden Academy cafeteria as SAD 22 representatives outlined ambitious plans for a new school. If approved, it would be the most expensive in state history.

The referendum vote will be held in each of the three SAD 22 towns from 8 a.m. to 8 p.m. Tuesday, Sept. 23, at their respective polling places.

The state Department of Education has approved $45 million for the project, while the SAD 22 building committee identified $6.2 million in additional local funding. The local share would cover a 900-seat performing arts center, a gymnasium larger than what the state would support, expanded science classrooms and laboratories, and an alternative-energy system.

The biggest concern Tuesday was not necessarily the cost, although that did come up, but rather the fact that the referendum does not separate state and local funding.

“Why is this vote all or nothing?” one man asked. “Why would you jeopardize all that state money?”

That comment came after SAD 22 representatives defended their plans and warned that if residents do not vote to approve the project, that $45 million in state money would be off the table.

“In my opinion, we would never see that money again for SAD 22,” Superintendent Rick Lyons said. “We cannot lose this opportunity.”

In response to the question of separating the two sources of funding, the school district officials defended the decision but said it was deliberated at length.

To SAD 22’s credit, the wording of the referendum vote is very specific as to what the $6.2 million in local funding will be used for. The affect on taxpayers varies slightly among the three towns but the average increase will be about $70 per $100,000 of property valuation for the first year. Any increase these days, though, is troubling.

Another concern was how much the new school would increase operating and maintenance costs. The answer was about $55,000 annually, although Lyons said the SAD 22 budget is put out to voters every year for approval anyway.

A site off Route 1A on land already owned by the school district has been approved for the project. It would create a de facto campus that includes all Hampden schools from kindergarten through grade 12. The initial plans call for a three-story, 172,247-square-foot building that would attempt to retain some of the old Hampden Academy’s charm.

SAD 22 has been working for 15 years to see this project finally approved for state funding.