A former Old Orchard Beach fire chief pleaded guilty Wednesday to arson for setting a fire last year that burned 42 acres of wetlands. Ricky Plummer, 61, entered the guilty plea to the Class A felony in York County Superior Court in Alfred. He is scheduled to be sentenced Jan. 9, said Deputy District Attorney Justina McGettigan. McGettigan said a lesser charge of failing to control or report a fire was dropped as part of a plea agreement with the York County District Attorney’s Office. Plummer changed his plea to guilty just five days before his trial was scheduled to begin.