At any time after the approval of a preliminary plan or a final plan of a development area, the owner or owners may request an amendment of their plans. The request for such amendment shall be filed with the Commission and one copy filed with the Clerk of Council. If such amendment is in substantial agreement with the approval of a preliminary or final plan, it shall be processed by the Commission. Should such amendment represent a departure from the intent of a prior approval, such amendment shall then be subject to the same procedure and conditions as the original application.