The sewer user charges established by resolution shall be reviewed biannually and revised periodically to reflect actual costs of operation, maintenance and replacement of the collection and treatment works and to maintain the equitability of the user charge based on the costs of operation and maintenance in proportion to each user's contribution to the total sewer flow. Each user shall be notified at least annually in conjunction with a regular bill that portion of his charge which is attributable to operation, maintenance and replacement of the collection system and that portion attributable to other costs. (Ord. 486, 6-10-1991)