Approval of the preliminary plat by the Council does not constitute approval of the subdivision but is merely an authorization to proceed with the preparation of the final plat. In the event the preliminary plat is approved and the final plat does not deviate from the preliminary plat plans and specifications and construction indicates improvements required by the City have been met or that satisfactory arrangements or escrow agreements have been made to assure construction of such improvements, then the final plat must be approved unless both the City and owner waive this agreement in writing.