State. Rep. Robert Brown has asked the state’s top lawyer whether the method by which the Mark Clark Expressway got its final piece of funding is legal.

Brown, D-Hollywood, said that’s important information for supporters and opponents of the controversial completion of Interstate 526 across Johns and James islands. If the South Carolina Transportation Infrastructure Bank doesn’t come through with the money, Charleston County could be stuck with a partially completed road project, he said.

The bank, a state agency that funds large transportation projects, in August approved an additional $138 million for the road, enough to cover its updated $558 million price tag. The bank will borrow money for the I-526 project by issuing bonds, but it has no bonding capacity left. The final $138 million for I-526 would come from money the bank could borrow after 2020.

It’s the bank’s counting on future revenue that may not be available in 2020 that concerned Brown. Last week, he wrote a letter to state Attorney General Alan Wilson, asking him whether “forward bonding” was legal. “It has statewide implications,” said Brown, whose district includes parts of Johns Island. “What if all state agencies did this?”

Wilson spokesman Mark Powell said the attorney general received the letter and is reviewing it. He doesn’t yet know whether Wilson will release an opinion on the matter, or when that might happen.

House Speaker Bobby Harrell, a strong supporter of I-526, pushed the bank board to approve the additional money for the project. Supporters said the money means the road, which they think is desperately needed for safety and to alleviate traffic, will be built.

Opponents have said I-526 likely would promote development and bring in more traffic than it would alleviate. They also said the money would be better spent on other road projects that are ranked as high priorities. I-526 is not ranked a state priority.

Brown said he was opposed to the parkway plan for I-526, which was the state Department of Transportation’s preferred alternative. But, he said, he has accepted that the road will be built after Charleston County Council approved it with a 5-4 vote in December. “I’m not debating the road anymore,” Brown said. “I’m debating the funding.”

In his letter, Brown also questioned whether a bank board member acted appropriately when he sent a letter to County Council members telling them that the county would be on the hook for $11.6 already spent on the project if the group decided against building the final leg of I-526.

The Infrastructure Bank, an independent agency that isn’t part of the state DOT, came under scrutiny this year after critics complained a disproportionate share of the money went to projects in Charleston and Horry counties, places where bank board members or those who appointed them live.

Bills have been filed in the Legislature this year to dissolve the bank’s board and assign its duties to the DOT.