Claimed errors in the calculation of assessments shall be called to the attention of the city manager, who shall determine whether there has been an error in fact. If the city manager shall find that there has been an error in fact, he shall recommend to the city council an amendment to the assessment ordinance to correct such error; and upon enactment of such amendment, the city manager shall make the necessary correction in the docket of city liens and send a correct notice of assessment by registered or certified mail. (1996 Code § 12.08.130)