In a planned unit development established under Chapter 169 of this Code of Ordinances, the Commission and the Council may modify or waive any of the minimum standards of design and development contained in Section 180.08 of this chapter to the extent that they find that such modification or waiver is not contrary to the interests of the City and necessary to achieve the purposes stated in Section 169.12 of this Code of Ordinances. As a condition to the modification or waiver of any of said minimum standards of design and development, the Commission and the Council may require that the developer enter into a contract for the future construction of any of the improvements set out in subsection 16 of Section 180.08 of this chapter. Such contract may provide either for construction of said improvements by the developer or for special assessment of the cost of said improvements against the property in the subdivision. Any modification or waiver of the minimum standards of design and development shall be specifically stated in the resolution establishing the planned unit development.