COLUMBIA — If South Carolina doesn’t raise nearly $30 billion in new revenue during the next 20 years to pay for highway repairs, replacement of bridges and mass transit, then the state’s Transportation Department will be left to manage the decline of the system, the man in charge of that mission said.

That assessment from Transportation Secretary Robert St. Onge is part of a report by an infrastructure task force that studied the issues for a year.

“If the decline is allowed to continue, congestion and load restrictions will result in irreparable damage to the state’s economy,” the report states.

The state’s transportation funding is so far below regional and national norms that most money goes to highway maintenance and upkeep, the report states.

“It’s a big, big deal,” said Ken Willingham of Mount Pleasant, who served on the task force. “I don’t know how you can help but notice how bad the roads are. We’re just so far behind on our infrastructure.”

Lawmakers must deal with the situation because the DOT Commission is not empowered to raise new revenue for highways, Willingham said.

Legislative leaders said they’re uncertain if transportation funding will be addressed next year in any meaningful way.

“I think the big bear when we go back in will be what to do about Medicaid expansion,” said Senate President Pro Tem John Courson. “Until we get Medicaid under control in South Carolina, I dont see us going off on any other spending plan.”

Sen. Mike Fair of Greenville, who serves on the Senate Finance Committee, said it’s possible the Department of Transportation a priority in the state’s budget. But that would require removing funds from another agency, he said.

“I don’t think it will be addressed right away,” he said. “We do need more revenues before we look at any major plan for funding.”

The state will need $48.3 billion over the next 20 years for its infrastructure needs, according to the report, including $17 billion for highway system maintenance, $22 billion for highway and interstate upgrades, $3 billion for bridge replacement and $3.9 billion for mass transit.

But officials only expect a total of $19 billion in revenue over that time period, meaning the state would need to find another $29.3 billion.

The state motor fuel tax, which has been 16 cents per gallon since 1987, is DOT’s main source of funding. Revenue from the tax has declined because of improved vehicle fuel efficiency and higher costs for gasoline and diesel fuel. If adjusted for inflation, the tax would be 33 cents today, the report states.

The fee for a state driver’s license, the lowest in the Southeast, could be increased by $1 to raise an additional $3.3 million annually. The automobile registration fee has been $12 for 25 years. A $1 increase in the fee would generate about $2 million a year.

Other possibilities suggested in the report include a surcharge of $1 per month on each insured vehicle, which could bring in about $42 million per year for highway safety improvements.

“The consequences of inaction are clear and predictable,” the report states. “Deterioration of roads and bridges, reduced highway safety, the posting or closing of bridges, increased traffic congestion, increased vehicle upkeep and a loss of economic competitiveness.”