In the event that a developer has obtained prior approval of a preliminary plat or sketch plan within two years of the date of filing the final plat, the developer shall file three copies of the final plat and supplementary materials with the City Engineering Department. The City Engineering Department shall check the plat and supplementary materials to insure compliance with the preliminary plat or sketch plan. If such final plat substantially complies with the preliminary plat or sketch plan, the City Engineer shall immediately approve the same.