(a) If additional costs are incurred that are chargeable to an assessment district after the initial assessment roll has been approved by the City Council, the City Manager may prepare and file with the City Clerk a supplemental assessment roll.

(b) Procedure for notice and public hearing for a supplemental assessment must conform to that utilized for the initial assessment.

(c) Billings and payments on a supplemental assessment shall be kept separate from the initial assessment. Supplemental assessments may have payment terms and due dates different from the initial assessment.

(d) More than one (1) supplemental assessment may be allowed.

(e) The sum of all supplemental assessments in any one (1) assessment district may not exceed twenty percent (20%) of the initial approved assessment roll.