The approval of a final development plan for a planned unit development shall be for a period not to exceed one year to allow for preparation and recording of the required subdivision plat and the development of the project. If no construction has begun within one year after approval is granted, the approved final development plan shall be void. An extension of the time limit or modification of the approved final development plan may be approved if the commission finds that such extension or modification is not in conflict with the public interest. (Ord. 15, 7-11-1977)