Nothing in N.M. Stat. Ann. Chapter 74, Article 1 limits or is intended to limit the authority of any county or municipality to adopt and enforce requirements related to on-site liquid waste systems that are at least as stringent as those in that article; provided, however, that the county or municipality has, on staff or under contract, either a registered professional engineer with education or experience in sanitary engineering or a class II wastewater operator certified by the state of New Mexico.