(3) The following service areas:
a. For the joint agency operated by the cities of Davidson and Mooresville, the service area is the combined areas of the city of Cornelius; the town of Troutman; the town of Huntersville; the unincorporated areas of Mecklenburg County north of a line beginning at Highway 16 along the west boundary of the county, extending eastward along Highway 16, continuing east along Interstate 485, and continuing eastward to the eastern boundary of the county along Eastfield Road; and the unincorporated areas of Iredell County south of Interstate 40, excluding Statesville and the extraterritorial jurisdiction of Statesville.