The Department is amending Chapter 62-303, F.A.C., to revise impairment thresholds and establish assessment methodologies for numeric interpretations of the narrative surface water criterion for nutrients in paragraph 62-302.530(47)(b), F.A.C. The proposed rule revisions also establish a new list type (Study List). OTHER RULES INCORPORATING THIS RULE: Chapter 62-303 and Rules 62-303.100, 62-303.150, 62-303.200, 62-303.310, 62-303.330, 62-303.350, 62-303.351, 62-303.352. 62-303.353, 62-303.354, 62-303.390, 62-303.420, 62-303.430, 62-303.450, 62-303.710, 62-303.720, F.A.C., are referenced by the following rules: Rules 62-302.530, 62-303.100, 62-303.150, 62-303.200, 62-303.300, 62-303.310, 62-303.320, 62-303.330, 62-303.350, 62-303.351, 62-303.352, 62-303.353, 62-303.360, 62-303.370, 62-303.380, 62-303.400, 62-303.410, 62-303.420, 62-303.430, 62-303.450, 62-303.460, 62-303.470, 62-303.480, 62-303.600, 62-303.700, 62-303.710, 62-303.720, 62-303.810, 62-304.100, 62-305.200, and 62-672.780, F.A.C. EFFECT ON THOSE OTHER RULES: This rulemaking does not have any direct effect on Rule 62-301.530, F.A.C. Rule 62-302.530, F.A.C., simply notes that Chapter 62-303, F.A.C., is the Department’s assessment methodology, and accounts for natural and statistical variability when assessing ambient waters pursuant to sections 305(b) and 303(d) of the Federal Clean Water Act. All of the rules listed for Chapter 62-303, F.A.C., are simply cross-rule references within the chapter, and this rulemaking takes into account the interconnection between rule sections for the planning, study, and verified lists. This rulemaking affects Rule 62-304.100, F.A.C., because it affects which waters are listed on the verified list for nutrient impairment. The Department is responsible for developing and adopting by rule in Chapter 62-304, F.A.C., Total Maximum Daily Loads (TMDLs) and their allocations for waters that have been verified to be impaired by a pollutant pursuant to Chapter 62-303, F.A.C. This rulemaking also affects Rule 62-305.200, F.A.C., because it establishes when nutrients are identified as a “pollutant of concern.” Rule 62-305.200, F.A.C., refers to Chapter 62-303, F.A.C., in the definition for “pollutant of concern,” which means “the pollutant or pollutants that have been identified as causing the impairment of a water body pursuant to the process set forth in Chapter 62-303, F.A.C.” This rulemaking also affects Rule 672.780, F.A.C., which requires that operating plans for new or increased discharges from phosphogypsum stack systems identify “any impaired waters and parameters included on a verified list, determined in accordance with Chapter 62-303, F.A.C., for any water body or water body segment existing at or downstream of the proposed new or increased discharge.”