All utility bills are due and payable in the office of the city clerk/treasurer upon receipt. Bills not paid within thirty days of the billing date shall be considered delinquent; provided, that when the thirtieth day falls on a legal holiday, Saturday or Sunday, the first business day thereafter shall be considered the thirtieth day. A fee in the amount set forth in Chapter 2.50 of this code will be added to any delinquent utility account that is served with a water shutoff notice. (Ord. 947-04 § 2).