It may seem ironic that public schools aren't exempt from Berkeley County's controversial transportation impact fee and a similar one in Dorchester County, which can range from thousands of dollars to hundreds of thousands for nonresidential development.

Impact fees are aimed at making new development pay for growth-related expenses, such as roads. School Districts across the tri-county area are building new schools to handle the area's fast population growth, and are being assessed impact fees because of the traffic associated with schools.

This year the Berkeley County School District paid $215,177 in transportation impact fees for Nexton Elementary School, for example, but like most school districts, Berkeley County School District is not allowed to collect impact fees on the new construction that creates the need for new schools.

The Dorchester 2 School District is an exception - an unconstitutional one, according to two homebuilder associations - because state legislation in 2009 allowed only that district to assess an impact fee on residential development.

"The taxpayers in this area were wanting a fee to be imposed, to help deal with the growth," said Allyson Duke, the school district's chief financial officer. "We're not going to turn down money to help with building programs."

With a fast-rising student population, the district is now using 186 manufactured-home style classrooms to handle the overflow. The district calls them "learning cottages" and at Knightsville Elementary, they now comprise most of the classroom space.

"With 37 trailers, we have more students outside the building than inside the building," said district spokeswoman Pat Raynor. "We do have facilities that are severely overcrowded."

The impact fee collected since mid-2009 has raised a little over $8 million, but the district hasn't spent the funds due to the ongoing lawsuit filed by The Home Builders Association of South Carolina and the Charleston Trident Home Builders Association. Preliminary motions in the case were appealed all the way to the state Supreme Court, which last year rejected the school district's attempt to have the challenge dismissed. The case is back at the starting point with both sides collecting information.

Charleston Trident Home Builders Association President Philip Ford said it's not fair to blame crowded schools on new construction.

"You can buy an existing home from a retired couple, and bring three or four kids with you, and you're not going to pay the Dorchester 2 School District $2,500," he said. "And that retired couple can buy a new home, and they will pay it."

One of the larger developers in the area now is MeadWestvaco, which is building the Nexton community with nearly 10,000 homes, and developing the 72,000-acre East Edisto property in Dorchester County. Ken Seeger, president of MeadWestvaco's Community Development and Land Management division, said the company isn't opposed to the school district's impact fee.

"Unlike the homebuilders (association), we supported the school impact fee," Seeger said in a recent interview. "You kind of need to help, when it comes to public infrastructure."

It could potentially take years to resolve the litigation over the impact fee. Builders also pay impact fees to water and sewer utilities, to municipalities including Mount Pleasant and Summerville, and to counties including Berkeley and Dorchester.

Added up, the impact fees on a single house can total $7,000 or more in the Dorchester 2 School District, and more than $8,000 in Mount Pleasant. Charleston County and municipalities including North Charleston have no impact fees.

"There has to be a balance," Seeger said. "There's only so much you can pass along before homes become unaffordable."

Reach David Slade at 937-5552