The secretary shall further categorize all public water systems with regard to the size, type, source of water, and other relevant physical conditions affecting purification plants and distribution systems to assist in identifying the skills, knowledge and experience required for the certification of operators for each category of such systems, to assure the protection of the public health and conservation and protection of the state’s water resources as required under RCW 70A.120.010, and to implement the provisions of the state safe drinking water act in chapter 70A.125 RCW. In categorizing all public water systems for the purpose of implementing these provisions of state law, the secretary shall take into consideration economic impacts as well as the degree and nature of any public health risk.