The utility shall calculate the impervious surface of each parcel of developed real property within the boundaries of the utility to determine the number of equivalent residential units contained therein; two thousand square feet of impervious surface shall equal one equivalent residential unit. All detached single-family residences and mobile homes are deemed to contain one equivalent residential unit. All multifamily residences are deemed to contain three-quarters equivalent residential unit per each living unit. For all other developed real properties within the utility boundaries, the utility shall determine the number of equivalent residential units contained thereon by dividing the number of square feet of impervious surfaces on each property by two thousand square feet per ERU; the total thus obtained will be rounded to the nearest half representing the equivalent residential units contained on such property. Each developed parcel of property shall be deemed to contain a minimum of one equivalent residential unit. (Ord. 947-04 § 2).