Coleman attended his last meeting as a Carrboro alderman Dec. 4, which is two years before his term is set to expire in December 2015.

A popular vote is required if an alderman leaves with one year or more left in his or her term, said Mayor Mark Chilton. The aldermen have to decide whether to hold a special election or wait until the town’s municipal elections in 2013.

“This has never actually happened before,” he said, “Before, [vacancies] were exclusively filled by the Board of Aldermen.”

Coleman was re-elected to a four year term in November 2011, but he announced in May that his family will be moving to Australia.

A special election must be approved by a board vote at the next meeting after the vacancy occurs.

Before a 2006 amendment, the town charter did not have procedures for handling board vacancies, nor did it authorize the board to call for a special election to fill vacancies.

Chilton said a special election will take political pressure off remaining board members to fill the vacant seat – as the Chapel Hill Town Council is doing with the council seat vacated by newly elected County Commissioner Penny Rich. But it will also amount to additional costs for the town.

The town has $11,000 budgeted for a special election and would have to transfer another $7,000 with a budget amendment, Town Clerk Cathy Wilson said in an email to the board.

The special election cannot be held in July through August but can take place as soon as March, she said. The municipal election is scheduled for November.

Notice of the election must be posted 45 days before the election date, she said in the email.

The Orange County Board of Elections allows the town 50 to 70 days to prepare for the elections, and the board requires seven days to confirm the results.

Damon Seils, first vice chairman of the Planning Board, announced in November that he will run for Coleman’s seat.

The board returns from winter break Jan. 15.