A. A class A county having a population of more than one hundred thirty-five thousand but less than four hundred eighty-one thousand according to the last federal decennial census, and having a 1993 net taxable value of property, as that term is defined in the Property Tax Code [Chapter 7, Articles 35 to 38 NMSA 1978], of at least one billion one hundred thirty-one million dollars ($1,131,000,000) but not more than five billion two hundred million dollars ($5,200,000,000) may establish, purchase, own and operate sewer and water utilities and sell water and sewer utility service.

B. In the operation of a sewer or water utility, the county shall set just and reasonable rates based on its cost of service.