(a) Planned Developments in any residential district may contain, in addition to those uses that normally would be permitted in the district for which the development is proposed, the following:
(1) Business and personal service uses as permitted in the "B-1" Local Retail District to the extent that they are designed and intended to serve the residents of the Planned Development.
(2) A mixture of types of buildings and structures, such as detached, semi-detached, attached, multi-storied, or any combination thereof.
(b) Planned Developments in the Office-Residential, Office-Commercial or Business Districts may contain a mixture of uses and types of buildings and structures.
(c) Planned Developments in Industrial Districts may contain only those uses that would be permitted in the district for which the development is proposed. The application shall contain an engineering study demonstrating that the proposed industrial uses will comply with the applicable standards imposed by the particular industrial district in which it is proposed to locate the Planned Development.