Approval of a plan submitted under the provisions of this Chapter shall expire one year after the date of approval unless construction has commenced in accordance with the plan. However, if prior to the expiration of the approval, the applicant makes a written request to the Zoning Administrator for an extension of time to commence construction setting forth the reasons for the requested extension, the planning department may grant one extension of not greater than one single year. Receipt of any request for an extension shall be acknowledged by the Zoning Administrator within 15 days. The Zoning Administrator shall make a decision on the extension within 30 days of receipt. Any plan may be revised in the same manner as originally approved.