A maintenance guarantee shall be posted with the City Council by the developer for a period not to exceed two years after final acceptance of the improvement in an amount not to exceed 15% of the cost of the improvements. The developer may elect to furnish such maintenance guarantee either by maintaining on deposit with the City 15% cash or certified check portion of the performance guarantee provided in accordance with § 215-70 of this article or by a bond issued by a bonding company or surety company, or other type of surety acceptable to and approved by the City Solicitor and City Council in an amount equal to 15% of the cost of the improvements. The maintenance guarantee shall be to the effect that the applicant, developer, owner or user guarantees the complete maintenance of all improvements for a period of two years from the release of his performance guarantee. Should he/she fail in his/her obligation to properly maintain all improvements, the City may, on 10 days' written notice or immediately, in the case of hazard to life, health or property, proceed with necessary repair or replacement of any unacceptable improvements and charge the cost thereof against the guarantee. At the end of the maintenance guarantee, the cash or certified check on deposit will be returned to the subdivider less any sum, properly documented by the City, which has been expended to repair or replace any unsatisfactory improvements.