Additional pro rata assessments may be made when any special assessment roll proves insufficient to pay for the improvement for which it was levied and the expenses incident thereto, or to pay the principal and interest on bonds or other evidences of obligation issued therefor; provided that the additional pro rata assessment shall not exceed twenty-five per cent of the assessment as originally confirmed unless a meeting of the Commission be held to review such additional assessment, for which meeting notices shall be published and mailed as provided in the case of review of the original special assessment roll.
Whenever any special assessment shall, in the opinion of the Commission, be invalid by reason of irregularity or informality in the proceedings, or if any court of competent jurisdiction shall adjudge such assessment to be illegal, the Commission shall, whether the improvement has been made or not, or whether any part of the assessments have been paid or not, have power to cause a new assessment to be made for the same purpose for which the former assessment was made. All proceedings on such reassessment and for the collection thereof shall be conducted in the same manner as provided for the original assessment, and whenever any sum or part thereof levied upon any property in the assessment so set aside has been paid and not refunded, the payment so made shall be applied upon the reassessment or if the payments exceed the amount of the reassessment refunds shall be made.
No judgment or decree nor any act of the Commission vacating a special assessment shall destroy or impair the lien of the city upon the premises assessed for such amount of the assessment as may be equitably charged against the same or as by regular mode of proceeding might have been lawfully assessed thereupon.