The final plat shall be accompanied by a set of construction plans as required in Section 1105.15. Prior to the granting of approval of the final plat, the subdivider shall have installed the minimum required improvements or shall have furnished a performance bond, certified check or letter of credit, to the City for the amount of the estimated construction cost of the ultimate installation and initial maintenance of the improvements. Before the bond, certified check or letter of credit is accepted, it shall be approved by the City Safety-Service Director and his legal counsel. The term of the bond, certified check or letter of credit shall extend twelve months beyond the completion date of the project unless released prior thereto by the appropriate officials. A completion date shall be established by the subdivider and approved by the appropriate officials. The period of time stipulated by the City Planning Commission to make final plat improvements shall not exceed two years from the date of the final plat approval unless an extension is requested in writing by the subdivider and granted in writing by the City Planning Commission.