Building one of the nation’s most expensive high schools could tax Lowell’s finances for years and has polarized residents worse than the 2016 presidential election, one city councilor told the Herald.

The unrest hasn’t stopped since the council voted 5-4 late yesterday to build an estimated $340 million high school at Cawley Stadium in the city’s upscale Belvidere neighborhood rather than renovate the existing 1920s-era building in downtown.

“I’ve never seen the city so polarized,” said Councilor William Samaras, who voted against Cawley. “It’s as bad as the Trump-Clinton election.”

Samaras, a former headmaster at Lowell High, said the school is needed — but a lot of questions remain to be answered surrounding the final bill and other projects that may now need to be shelved.

The proposed five-story high school would require an 8-percent hike in property taxes, or roughly a $250 to $300 minimum annual tax increase for homeowners. Businesses could face an estimated annual jump of $2,000 more in taxes. The losing downtown option would have cost $353 million, with the city paying $143 million.

The plan still has to be submitted for approval to the Massachusetts School Building Authority, which is expected to take up the project in August. If approved, the state would reimburse the city for about 55 percent and the city would pay the remaining $149 million. The City Council also has to approve a $160 million bond for the project cost.

The school is designed to house more than 3,000 students and would be the most expensive high school proposal in the state, if approved. It would also come during a building boom.

“The cost of construction in Massachusetts has been rising dramatically because there is so much construction going on,” said Laura Wernick, a senior principal at HMFH Architects in Cambridge. “These urban schools tend to be more expensive. Logistically, it is more complicated to work in a city. Sites tend to be smaller. There is not much large public space to build.”

Some Lowell leaders worry the project costs could continue to escalate — jeopardizing the project entirely.

City Councilor Corey Belanger — who supported the relocation — said the unexpected could catch Lowell by surprise.

“God forbid we have another emergency,” Belanger said. “We have 29 other schools. We need a police station desperately. If anything goes wrong, it will take another tax increase and we’ll be at the levy.”

He also worried about the hit on taxpayers.

“If it gets any more expensive, we may have to reconsider,” he said. “I have to stay flexible. I have an obligation to the taxpayers.”