Modifications.
Upon request or its own motion, Council may grant a modification or waiver of the requirements of one or more provisions of the planned residential development provisions of this chapter where a rational and reasoned basis for such modification is shown, provided that such modification will not be contrary to the public interest and that the purpose and intent of the planned residential development provisions of this chapter are observed. Any request for any such modification shall state in full the grounds and facts of unreasonableness or hardship on which the request is based, the provision or provisions of the ordinance involved, and the minimum modification necessary.

Time limitations and revocation.
The continuing validity of any approval of plans in accordance with this chapter shall be subject to those limitations established by Section 508(4) of the Planning Code. Both tentative and final approval (if any) of the development plan shall be revoked if the developer gives notice of his intention to abandon the plan.