The sewer user rates for each user (or user class) shall be based on the user's contribution to the total wastewater loading of the treatment facilities in comparison to a standard equivalent user as defined below. Each user (or user class) shall be assigned a number of equivalent users to be multiplied by a constant monthly cost factor to determine the basic user monthly rate. Special users contributing sewage of excessive flow and/or strength, for which the tabulated equivalent users below do not apply, shall be individually calculated as provided below. (Ord. 284, 1980)