Phasing. Where a project is proposed for construction in phases, the planning and designing shall be such that, upon completion, each phase shall be capable of standing on its own in terms of the presence of services, facilities, and open space, and shall contain the necessary components to ensure protection of the health, safety, and welfare of the users of the PUD and the residents of the surrounding area. In addition, in developments which include residential and nonresidential uses, the relative mix of uses and the scheduled completion of construction for each phase shall be disclosed and determined to be reasonable in the discretion of the Plan Commission.