COLUMBIA — The future of an extension of Interstate 526 in Charleston is in doubt after the South Carolina Department of Transportation refused Wednesday to take over the $558 million project.

The SCDOT Commission unanimously rejected the project, with several members upset that the Charleston County Council tried to turn funding for the road over to the state.

Officials announced in January they wanted the state to take over the project because Charleston County couldn’t agree on how to finish the final link of the highway between James Island and Johns Island in the western Charleston suburbs.

Opponents of the road said it is unnecessary and would lead to South Carolina spending more money in the Lowcountry than other areas of the state. A group that opposes what the new road could do to the neighborhoods west of Charleston also mounted a campaign against the state paying for the highway.

The decision leaves Charleston County trying to figure out how to pay for the final eight miles of I-526, if leaders choose to do the project at all.

Charleston Mayor Joe Riley gave a presentation to the DOT board, saying the highway was vital for both hurricane evacuations and assuring Charleston continues to grow by keeping its roads unclogged.

He likened the final leg of I-526 to part of a coronary bypass, saying if the project wasn’t approved, the region would suffered a heart attack.