The department is amending Chapter 62-303, F.A.C., to update the listing methodology for assessing human health-based water quality criteria as part of the process to identify impaired surface waterbodies. This rulemaking is being conducted in conjunction with rulemaking to revise the human health-based criteria in Chapter 62-302, F.A.C. (noticed under a separate rulemaking notice). The proposed revisions to Chapter 62-303, F.A.C., are designed to revise the assessment methodology to be consistent with the proposed change in the expression of the human health-based water quality criteria for non-carcinogens from single sample maximums to annual averages (proposed concurrently as changes to Chapter 62-302, F.A.C.) and to add a minimum sample size for the calculation of an annual average. Additionally, in accordance with the requirements of paragraph 403.061(29)(b) and paragraphs 403.861(21)(a) and (b), Florida Statutes, enacted under Chapter 2016-01, Laws of Florida, the department is proposing to establish a new sub-classification of surface waters (Class I-Treated, Treated Potable Water Supplies), which will require minor revisions in Chapter 62-303, F.A.C. Specifically, the department plans to revise a number of rules in Chapter 62-303, F.A.C., to clarify that Class I waters include both “Class I” (existing Class I waters) and “Class I-Treated” (Treated Potable Water Supply waters).