Rule 62-303.390. The Study List

(1) The Study List contains waters where additional information or Department review is needed before the water is placed on the Verified List for TMDL development but available evidence indicates nonattainment of water quality standards or stream nutrient thresholds. Causes of nonattainment can include excess pollutant loading or concentrations, habitat or hydrologic alterations, or natural conditions. Waters that do not attain water quality standards due to natural conditions pursuant to Rule 62-303.420, F.A.C., shall not be added to the Study List. To conform to the expectations of Section 303(d) of the Federal Clean Water Act and federal regulations at 40 C.F.R. 130.7(b), waters and associated parameters identified in the Study List will be submitted to EPA as water quality limited segments. However, pursuant to Section 403.067(2)(a), F.S., the Study List cannot be used in the administration or implementation of any regulatory program. A TMDL shall not be established by the Department for a waterbody placed on the Study List pursuant to subsection 62-303.390(2), F.A.C., until such time as it is placed on the Verified List pursuant to Part IV of this chapter.

(2) A Class I, I-Treated, II, III or III-Limited water shall be placed on the Study List if:

(a) For waters with a statistically-significant increasing trend in TN, TP, nitrate-nitrite, or chlorophyll a pursuant to paragraph 62-303.352(1)(c), F.A.C.; or, subsection 62-303.351(5), 62-303.353(4) or 62-303.354(3), F.A.C., the Department confirms the water does not exceed an applicable numeric nutrient criterion and there is a reasonable expectation that the water will become impaired within 10 years, taking into consideration the Sen-Theil fitted line based on the annual geometric means in the assessment period and the magnitude of the applicable criterion. For lakes that do not have a site specific numeric interpretation of the narrative nutrient criterion, the applicable TN and TP nutrient criteria shall be the maximum numeric interpretation for the applicable lake color and alkalinity category.

(b) A waterbody does not achieve the Biological Health Assessment provisions in Rule 62-303.430, F.A.C., but a cause has not been identified;

(c) A waterbody is verified as not meeting the dissolved oxygen criterion pursuant to Part IV of this chapter, but a cause has not been identified;

(d) A waterbody where pollution control mechanisms are in place or planned that meet the requirements of subsections 62-303.600(1) and (3), F.A.C., or that implements an existing total maximum daily load through a basin management action plan, or a Department enforcement order, except that there is uncertainty when water quality standards will be attained and the waterbody segment requires additional study;

(e) For streams meeting the definition in subsection 62-302.200(36), F.A.C., that do not have a site specific numeric interpretation of the narrative nutrient criterion, the nutrient thresholds in subparagraph 62-302.531(2)(c)2., F.A.C., are exceeded based on data from the last 7.5 years and insufficient Biological Health Assessment, chlorophyll a, or other response variable data are available to fully assess achievement of the nutrient provisions in paragraph 62-302.531(2)(c), F.A.C.

(f) For streams meeting the definition in subsection 62-302.200(36), F.A.C., that do not have a site specific numeric interpretation of the narrative nutrient criterion, there is an exceedance of the LVS floral metric, as described in the document titled “Implementation of Florida’s Numeric Nutrient Standards for Streams, June 2025” (incorporated by reference in subsection 62-302.200(36), F.A.C.) but the LVS results cannot be linked to anthropogenic nutrient inputs.

(g) There are fewer than twenty samples for a bacteriological water quality criterion expressed as a TPTV, but there are five or more samples that do not meet an applicable water quality criterion based on data from at least five temporally independent sampling events;

(h) A waterbody segment is verified as not meeting the bacteriological water quality criterion pursuant to Part IV of this Chapter, but the Department determines that additional study is needed to evaluate whether the exceedances are due to natural sources given the predominance of natural land uses in the watershed or based on information submitted to the Department, or

(i) A waterbody exceeds a generally applicable criterion, but the Department receives a petition for a SSAC pursuant to Rule 62-302.800, F.A.C., and additional time is needed to review and process the petition.

(j) For streams that do not meet the definition in Rule 62-302.200, F.A.C. and that do not have a site specific numeric interpretation of the narrative nutrient criterion, the nutrient thresholds in subparagraph 62-302.531(2)(c)2., F.A.C., are exceeded based on data from the last 7.5 years or sufficient Biological Health Assessment, chlorophyll a, or other response variable data are available to fully assess achievement of the nutrient provisions in paragraph 62-302.531(2)(c), F.A.C. are exceeded, but the Department receives a request from stakeholders for the waterbody to be excluded from the stream numeric nutrient criterion and additional time is needed to review and process the documentation.

(3) For waters placed on the Study List based on an increasing trend in nutrients or chlorophyll a pursuant to paragraph 62-303.390(2)(a), F.A.C., the Department shall notify local stakeholders about the increasing trend. A water shall be removed from the Study List upon development of a new site-specific interpretation of the narrative nutrient criteria for the waterbody that would address the trend, determination that there was a flaw in the original analysis, determination that there is no longer a statistically-significant increasing trend (at the 95 percent confidence level) for the two most recent listing cycles; development of a restoration plan meeting the requirements of subsection 62-303.600(1), F.A.C., that would address the trend; or placement of the water on the Verified List.

(4) For waters that meet the listing requirements under paragraph 62-303.390(2)(a) or (b), F.A.C. above, a stressor identification study shall be conducted to identify the causative pollutant(s) or other factor(s) responsible for nonattainment. A stressor identification study includes collection and analysis of physical, chemical, and biological data necessary to determine the causative pollutant(s) or other factor(s) causing nonattainment.

(5) For waters placed on the Study List based on exceedances of the nutrient stream thresholds pursuant to paragraph 62-303.390(2)(e), F.A.C., sufficient biological health assessments shall be collected to determine whether the stream attains the stream nutrient standard in paragraph 62-302.531(2)(c), F.A.C.

(6) For waters that fall under paragraph 62-303.390(2)(e), F.A.C., above, the Department shall conduct a site-specific assessment of the stream to determine potential causes of the nuisance macrophyte growth.

(7) For waters that fall under paragraph 62-303.390(2)(g), F.A.C., above, additional samples shall be collected to meet a minimum of 20 samples to re-assess the waterbody.

(8) For waters that fall under paragraph 62-303.390(2)(h), F.A.C., above, a bacterial source tracking study shall be conducted to evaluate whether anthropogenic sources are causing exceedances of the bacteriological criteria. The water shall be removed from the Study List if the Department confirms the exceedances are due to non-anthropogenic sources or shall be verified as impaired if at least ten percent of the exceedances are demonstrated to be due to anthropogenic sources.

(9) For waterbodies placed on the Study List to provide time to complete the review and otherwise process a petition for a SSAC, the Department shall reassess the waterbody during the next applicable assessment cycle for the basin.

(10) It is the Department’s goal to collect the additional data needed for waters placed on the Study List pursuant to paragraphs 62-303.390(2)(a) and (b), and (2)(d)-(h), F.A.C., as part of its watershed management approach, with the data collected during either the same cycle that the water is initially listed on the Study List or during the subsequent cycle. After collecting the additional data, the Department shall either list the waterbody on the Verified List or remove the waterbody from the Study List, as appropriate. Rulemaking Authority 403.061, 403.067 FS. Law Implemented 403.062, 403.067 FS. History–New 7-2-12, Amended 2-17-16, 10-17-16, 11-25-25.