Advocate file photo by BRYAN TUCK -- Carencro Mayor Glenn Brasseaux speaks at a dedication cermony for the Veterans Memorial in November 2014.

Carencro residents could be facing a new sales tax or an increase of up to $84 a month on their sewer bills to fund a new sewage treatment plant to keep up with a spate of new residential developments in the city.

“We are at capacity now, and we are looking at 600 more homes at this time next year,” said City Manager Jay Castille.

Carencro’s growth has been moderate but steady in recent years, climbing from 6,159 residents in 2000 to its current population of more than 8,300.

But the city is preparing for a big growth spurt as developers take more interest in northern Lafayette Parish.

To accommodate the new homes and businesses, city officials are planning a new sewer treatment plant estimated at $24 million to $26 million.

That’s about twice the city’s annual budget of $12 million, Castille said.

Carencro Mayor Glenn Brasseaux said the city has applied for a loan from the U.S. Department of Agriculture to pay for the new sewer plant, but significant new revenue would be needed to pay the debt.

City officials are considering two alternatives: adding $65 to $84 a month to sewer bills for the foreseeable future or asking voters to approve a news sales tax.

Most residents won’t like either option, the mayor concedes, but the city might be facing stiff fines for environmental violations if a new treatment plant is not online within the next few years.

“We are in a quandary,” he said.

The combined monthly water and sewer bill for most Carencro residents is now about $20, so an extra $65 to $84 could put bills in the $85 to $100 range.

“You know, nobody can afford that,” Brasseaux said.

He said a new one-cent sales tax could pay for the new sewage treatment plant and possibly generate enough extra revenue for a new fire station and firefighting equipment, another need created by the city’s growing population.

The advantage of the sales tax is that nonresidents who shop in the city would also help pay the debt, Castille said.

“Everybody shares that way,” he said.

A new one-cent sales tax would bring the sales tax rate to 10 percent in the area along Interstate 49 in Carencro, where a special taxing district is in place, and up to 9 percent in the rest of the city.

Brasseaux said he expects some decision to be made before year’s end on how to move forward.

In the meantime, he said, the city has begun designing the new treatment plant.

“We have been trying to be proactive,” the mayor said. “If we don’t do anything, probably in a short while we will get fined.”

Follow Richard Burgess on Twitter, @rbb100.