In Hamilton County, churches, schools and government agencies don’t pay the stormwater fee on their buildings and parking lots.

But in Chattanooga, they do — or at least most do.

The differing standards on who pays the stormwater fee and who doesn’t in Hamilton County has raised questions — and could generate some lawsuits.

Chattanooga public works officials say the city imposes its stormwater fee on any building or developed acreage where a lack of vegetation might aggravate rainfall runoff or allow stormwater to mix with oil residue, pesticides or other contaminants and flow into nearby creeks and streams. That includes churches, schools and nonprofit agencies that normally don’t pay property taxes.

For Hamilton County’s school system, the city’s stormwater fees are going up from $115,000 last year to $385,000 this year. Board of Education Chairman Kenny Smith said the extra cost was not budgeted this year.

“Those costs are going to have to come from our reserves and from the classroom,” he said. “That’s a very hard cost to absorb at this time of the year.”

The extra school expense is because of the city’s stormwater fee increase for schools within Chattanooga. Schools outside the city don’t pay any stormwater fee because the county’s program doesn’t charge fees on any church, school or nonprofit agency that doesn’t pay property taxes.

“The county decided not to charge fees on tax-exempt properties, but the city has taken a different approach,” said Tim McDonald, program manager for Hamilton County’s stormwater program.

While the city tries to impose its stormwater fee on all properties, one major property owner — the University of Tennessee at Chattanooga — has never paid the city fee since it began in 1993.

“We contend that the university should not be charged this fee,” said Robbi Stivers, the university’s director of real estate administration in Knoxville.

The city has billed UTC for stormwater fees but has not challenged the university’s refusal to pay, according to Richard Beeland, a spokesman for Mayor Ron Littlefield.

“At this point, we’re evaluating our options,” he said. “We’re not sure if they are exempt or not.”

One business that is exempt from paying the stormwater fee is Chattanooga’s newest — and one of its biggest — companies — Volkswagen of America.

Under Volkswagen’s agreement with the city and county, fees or taxes on its site in the Enterprise South industrial park are to be paid by local governments — not VW, Mr. Beeland said. So even though Volkswagen is building a 1.9 million-square-foot plant with acres of surrounding parking lots and support facilities, Volkswagen will pay no stormwater fees — at least for the next 30 years.