All revenues, except those from inspection fees, resulting from the rates and charges authorized by the sewer regulation ordinance shall be kept separate and apart from all other funds and shall be used for the construction, addition, improvement, financing, operation and maintenance of the sewer system of the City and the reserves shall be used for depreciation to the sanitary sewer facilities. [BC 4.04.025, amended by Ordinance No. 3387, 8/13/84]