When it is deemed necessary to make a public improvement to be paid for in whole or in part by special assessment, the Council shall declare the necessity therefor by resolution, and such resolution shall state the total estimated cost of the improvement and the amount thereof to be assessed, the method of assessment, the mode of payment, the number of annual installments and whether the assessments shall be by district or upon abutting, adjacent and contiguous or other specially benefited property, and such resolution shall be concurred in by three-fourths of the members of the Council. Such resolution shall be certified to the Finance Director, who shall thereupon proceed to make an assessment report, in accordance with the method of assessment provided for in the resolution, which report shall be filed with the Council, and which report shall show the lots and lands assessed, the amount of the assessment as to each, and the number of annual installments, not exceeding twenty, in which such assessments shall be paid. In no case shall the number of installments be greater in number than the estimated life of usefulness of the improvement as certified by the Finance Director.