If the requirements set forth in this Part are not met by the Subdivider within one year from the date of final approval, such approval shall be null and void. This time period may be extended for additional six-month periods by the City Manager. The Subdivider must petition for an extension prior to the expiration of the original one year or an extension previously granted. An extension may be granted only if the City Manager finds that it will not be detrimental to the City. If any of the fees charged as a condition of Subdivision approval, including but not limited to inspection fees, Flood control fees, or the amounts the City uses to estimate bonds to insure completion of improvements, have increased, the City Manager may require that the Subdivider pay such increases as a condition of granting the extension.