Minor changes in the location, siting or character of buildings and structures may be authorized by Council, if required by engineering or other circumstances not foreseen at the time the final development program was approved.  No change authorized under this section may increase by more than ten percent, or decrease by more than twenty percent, the size of any building or structure, or change the location of any building or structure by more than ten feet in any direction.  Council shall not permit changes beyond the minimum or maximum requirements set forth in this Zoning Code.
   All other changes in the Planned Unit Development, including changes in the site plan and the development schedule, must be made under the procedures that are applicable to the initial approval of the Planned Unit Development.