The City will review the storm water service charges at least yearly and revise the storm water service charges as necessary to ensure that such charges as herein established and specified generate adequate revenues to pay the costs of the maintenance and operation (including replacement and debt service) of a storm water management system and facilities and that the storm water service charges continue to provide for proportional distribution of maintenance and operations cost (including replacements costs and debt service) for a storm water management system and facilities among the users and users classes. The liability of a storm water service user to pay for charges as provided in this chapter shall be contingent, however, upon any such review or revision.