The Belfast City Council unanimously approved zoning changes Tuesday for a proposed large-scale salmon farm, over objections from an overflow crowd of residents who urged the city to wait.

Norway-based Nordic Aquafarms has proposed to build a land-based aquaculture facility on Route 1 at an estimated cost of $125 million to $500 million. The company expects to produce 33 million pounds of Atlantic salmon per year that would be sold to food markets in the Northeast.

Zoning changes approved by the council would allow industrial uses on a proposed, 40-acre site to be used for industrial purposes similar to those approved for the nearby Mathews Bros. window factory.

The development still must be approved by the Planning Board, which will review the fish farm proposal against standards for stormwater management, noise, light, vegetation buffers and other criteria.

Councilors backed the changes for the promise of new tax revenue and a chance to embrace new technology.

In an hour-long introduction, City Planner Wayne Marshall tried to head off concerns that have come up publicly since the fish farm was announced in January.

Setback requirements would narrow the 40 acres that Nordic Aquafarms proposes to buy to about 30 usable acres of which 70 percent could be covered by buildings and parking lots. Under terms of the land deal between the city, the water district and the aquaculture company, Belfast would retain a 250-foot wide strip of land along the north bank of Little River, including a popular hiking trail there. That land adds about 20 acres that will remain undeveloped, Marshall said.

“So, if you look at the whole,” he said. “10 acres are already off the table … Then you add the 20 acres next to it and you get down somewhere close to 50 percent (of the land available to be developed).”

Many residents have voiced concerns about the amount of fresh water the farm would require. Marshall said estimates from the Water District showed the city’s usage dramatically below the capacity of the aquifer demonstrated in years when food-processing industries were active in the city.

Upward of 60 people attended Tuesday night’s meeting. Many had to watch from the hallway outside the council chambers or an adjacent conference room where televisions were tuned to the meeting. Of the 27 people who spoke, all but three voiced concerns about the fish farm.

Reasons ranged widely. Some worried that the city was returning to industrial food production as in the days of the poultry and sardine processing factories. Others objected to the clearing of a large area of undeveloped forest and its effect on animal habitats and a popular hiking trail. Speakers were hesitant to embrace the counterintuitive idea of raising fish on land. Some warned of the environmental impact of large-scale animal farming, There were doubts about land-based fish farming and fears about pollution from the aquaculture facility – one speaker invoked an image of massive amounts of sludge being spread across the county.

Though the discussion was civil, speakers were sometimes pointed in their characterization of the salmon farm, calling it a “fish tank industrialized food business,” a “factory farm enterprise,” a “predatory industry,” “an experiment,” and, quoting from Henry David Thoreau’s reflections on working more than one must, a “mess of pottage.”

Shared by nearly everyone who spoke against the zoning change was a feeling that the council, in one way or another, should wait – for more information from Nordic Aquafarms, for residents to get up to speed on a project that city officials were able to study for months behind closed doors, leading up to the public announcement in January.

“I just have a simple question,” Ernie Cooper of Belfast asked the council. “What’s the rush?”

The five city councilors also differed in their reasons for approving the zoning changes, but likewise shared a single feeling: that the city doesn’t have the option to wait.

Two residents who spoke in favor of the salmon farm pointed to Norway’s higher ranking than the U.S. on environmental stewardship and many quality of life measures. But others questioned the idea that being from Norway is enough. Lane Fisher of Belfast said she would want to know if sound ethics crossed oceans.

“I don’t know how the good Norwegians operate when they’re in another country with different rules,” she said.