Special permit granting authority (SPGA). Unless specifically designated otherwise, the Zoning Board of Appeals shall act as the SPGA. The Planning Board is the SPGA for infill development, the Smart Growth PUD, Development Overlay District 1, open space residential developments, Groundwater Protection Overlay District, Surface Water Protection Overlay District, Large-Scale Ground-Mounted Solar Photovoltaic Overlay District, marijuana establishments, senior residential development, drive-through or drive-in businesses, and the Mill Street Corridor Development Overlay District. One associate member may be appointed to the Planning Board by the Mayor, subject to the confirmation by the City Council. The Chairperson of the Planning Board may designate the associate member to sit on the Board for the purposes of acting on a special permit application, in the case of absence, inability to act, or conflict of interest on the part of any member of the Planning Board or in the event of a vacancy on the Board.