In the event that within 18 months following approval by the city council, the applicant does not proceed with substantial construction in accordance with the plan so approved, the planning commission may initiate action to rezone the property. A public hearing, as required by law, shall be advertised and held, at which time the applicant shall be given an opportunity to show why construction has been delayed. Following the hearing, the planning commission shall make findings of fact and an appropriate recommendation to the city council.