If a project plan has not been approved within two (2) years of the establishment of the PO zone to a specific property, the Planning Commission will automatically initiate a rezoning action to revert said property to the zone existing on said land prior to the establishment of the PO zone. An approved project plan or preliminary project plan shall be in effect for all PO zones. In the event an approved project plan or preliminary project plan expires, a rezoning action to revert said zone shall be initiated.