The City will review the stormwater management fees at least yearly and revise the stormwater management fees as necessary to ensure that such charges as herein established and specified generate adequate revenues to pay the costs of maintenance and operation (including replacement and debt service) of stormwater management systems and facilities and that the stormwater management fees continue to provide for the proportional distribution of maintenance and operation costs (including replacement costs and debt service) for stormwater management systems and facilities among the users and user classes. The liability of a stormwater service user to pay for charges as provided in this chapter shall not be contingent, however, upon any such review or revision.