Voters will decide the fate of Billerica’s town center face lift at a special election on Monday. Town Meeting member George Simolaris has appealed Town Meeting’s Oct. 16 decision to spend $9.8 million on town center improvements. Simolaris submitted a petition with approximately 1,400 signatures, well over the 1,250 certified signatures required to force the Board of Selectmen to call a special election. According to town clerk Shirley Schult, to override Town Meeting’s decision, at least 20 percent of the town’s 26,217 registered voters must cast ballots in the special town election and a two-thirds majority of those voters must vote in the negative. If fewer than 20 percent of the town’s voters participate in the special election, the results will be nonbinding, she said.