Learn More: Impaired Waters

What does this mean?

The Clean Water Act (CWA) was passed by Congress in 1972. The US Environmental Protection Agency (EPA) enforces the CWA, which puts requirements on the States to protect water quality.

Section 303(d) of the CWA requires states to submit to EPA lists of waters that do not meet applicable water quality standards, to identify pollutant(s) that are causing or are expected to cause impairment, and to establish and implement plans to address these pollutants on a prioritized schedule.

Florida is delegated responsibility for complying with the CWA, and the State codifies its water quality rules in Chapter 62-303 of the Florida Administrative Code (FAC). The Florida Impaired Waters Rule (IWR) establishes a methodology to identify those waters that will be included on the State's "Section 303(d) list" of impaired waters that is required to be reported to EPA.

The EPA has established its own pollutant limits, separate from FDEP's, for many Florida waterways, and these federal TMDLs (see below) are enforced via compliance with municipal stormwater permits.

The Watershed Assessment Section (WAS) is the branch of the Florida Department of Environmental Protection (FDEP) that designs monitoring plans and collects water quality data in order to determine whether water bodies are meeting the water quality standards defined in Chapter 62-302 of the Florida Administrative Code.

When monitoring shows that a pollutant exceeds the allowable limit defined in the FAC, the WAS deems it "impaired" for that pollutant, adds it to the "303(d) List" and the "Verified List" (see below) and assigns it an impairment status. Updates to the 303(d) list are submitted to the EPA annually.

A description of FDEP’s listing/delisting process can be found on this page of FDEP's website.

The status values in the table below are used to explain the status of the impaired water bodies that appear in the WAS database known as Waters Not Attaining Standards (WNAS). More information about the reasons behind the status of each water body can be found in the "Comments" column of the WNAS database and the assessment lists that can be downloaded from the FDEP website. If a waterbody-pollutant is to be "delisted" from the "Verified List", FDEP may (or may not) request EPA's approval to remove it from the 303(d) list, and FDEP may (or may not) move the water body-pollutant to a different list, depending on the reason(s) for the delisting.

Status Value(s) Meaning
• Analysis Flaw
• Delist (Analysis Flaw)
Either the assessment data or its interpretation was flawed. Delisted water bodies are to be removed from the Verified List, but may be retained on the Study List for reassessment.
• No Causative Pollutant
• Delist (No Causative Pollutant)
While the effects of pollution may be evident, analysis was unable to identify the source of the pollution in order to correct the impairment. Or, there is impairment, but assessment has determined that it is not being caused by a pollutant. If delisted, the water body/impairment may be retained on the 303(d) List and/or put on the Study List for re-assessment.
• Ongoing Restoration Activities
• Delist (Ongoing Restoration Activities)
The water body has recently-completed or ongoing restoration activities to restore its designated uses. The water body is still included on the 303(d) list, but inclusion on the Verified List is postponed for two biennial assessment cycles (4 years), to allow for restoration to be completed and its success in removing impairments to be evaluated.
• Study List
• Delist (Study List)
Information is needed to determine the cause or degree of impairment, and while the water body will remain on the 303(d) list, it is being removed from the Verified list pending further assessment of the water body.
• TMDL Complete
• Delist (TMDL Complete)
A Total Maximum Daily Load document has been completed for the water body, and water resource managers are following its recommendations in order to eliminate the impairment. Though removed from the Verified List, the water body remains on the 303(d) list.
• Impaired The water body is not meeting its designated uses and action is needed to restore them.
• Reasonable Assurance A Reasonable Assurance Plan has been created by the water body's stakeholders and approved by DEP. Stakeholders are taking the actions defined in the plan to address the impairment(s) and enable the water body to attain its designated uses.

More Information:

  • The Integrated Water Quality Assessment for Florida ("303(d) List") identifies waters and their impairments that, by law, must be submitted to the EPA every two years. Regardless of which of the other lists a waterbody appear on, if it is on the 303(d) list, it is still considered by the EPA to be impaired. Removal from the 303(d) list requires concurrence by EPA.
  • The waterbodies on the Verified List are currently considered by FDEP to be impaired and are actively being assessed or re-assessed.
  • The waterbodies on the Delist List are in the process of being removed from the Verified List for a particular pollutant. Possible reasons for removal from the Verified List:
    • A mistake was made in the original assessment.
    • The regulatory limit that was exceeded originally has since been changed or eliminated.
    • A plan to reduce the pollution causing the impairment is being implemented. Some examples are ongoing restoration activities, a Total Maximum Daily Load (TMDL) document, or a Basin Management Action Plan (BMAP).
    • Recent assessment shows that water quality has improved and the waterbody now achieves its designated uses.
  • If FDEP considers a water body to no longer be impaired, it may request that EPA remove it from the 303(d) List.
  • The waterbodies on the Study List require additional information to determine whether they are meeting regulatory standards for a particular pollutant; they are included on the 303(d) list but not on the Verified List.
  • The waterbodies on the Study List Removals List do not meet the requirements for impairment and are to be removed from the 303(d) list. Reasons include more recent or accurate data, flaws in the original analysis, development of site-specific data or information to support natural conditions, and improvement in water quality conditions.

How are the data collected? (Methods)

Until 2020, the Florida Department of Environmental Protection's Watershed Assessment Section used a five-phase cycle that rotated through 29 basins throughout the state over a five-year period (all water bodies were assessed once every five years). However, in 2020 the FDEP changed its approach for assessing waters and under the new process, all of the basins in Florida are assessed simultaneously every two years.

FDEP's Integrated Water Resource Monitoring Network (IWRM), monitors Florida's water at three spatial scales or "tiers". Tier I relates to the state as a whole. Tier II includes basin-scale monitoring to identify and confirm impaired waters. Tier III consists of site-specific monitoring to determine regulatory compliance. Monitoring is performed at the FDEP District level and the resulting data are submitted to the Watershed Information Network's database for use by the Watershed Assessment Section.

Implementation of the numeric nutrient criteria requires two to three years of data to assess a water body, rather than the single year of data used under previous rules. As a result of this data sufficiency requirement, in most years, each of FDEP's six districts will be monitoring in multiple basins.

Many types of data are collected in an effort to determine whether or not a water resource is impaired. Sampling is conducted by the Watershed Assessment Section, supported by environmental scientists employed within individual Districts.

Biological data includes information about algae, bacteria, plants and other wildlife:

  • Algae sampling generally involves filtering water samples through special glass-fiber filters; these filters "trap" algal cells so they can be analyzed for chlorophyll concentrations in the laboratory.
  • Bacterial monitoring involves the collection and filtration of surface water samples, and the incubation of the filtrate (bacteria caught by the filter). After incubation, colonies of indicator bacteria (i.e., fecal coliform, total coliforms, etc.) appear as clusters of red or blue dots (depending on the type of test you use) on the filter. These colonies are counted, and an assessment can then be made about whether the water body is a potential health risk.
  • The term "wildlife" includes birds, fish, macroinvertebrates, etc., which are usually monitored by counting the number of different species and their actual abundance living in a water resource. The presence or absence of some animals is often an indicator of water resource health. For more on this, see the Macroinvertebrates "Learn More".

You can find Biology Reports by using the FDEP Bureau of Laboratories Report Search tool.

Water chemistry data are also obtained from in-situ (i.e., within the water) and lab analyses of surface water samples. This includes analyses for various forms of nitrogen and/or phosphorus—two essential nutrient groups found in virtually all water bodies. Tests are also performed to detect the presence of metals (lead, iron, etc.), pesticides, and other chemicals.

Physical characteristics indicating water clarity like turbidity and suspended solids are measured. Good water clarity is necessary for light penetration into the water column, allowing aquatic plants to photosynthesize. The amount of oxygen dissolved in the water is measured; both plants and animals that live in water require oxygen for respiration.

Water chemistry/physical data can be found in the FDEP Watershed Information Network (WIN) database (2017 and later) and/or in the Florida Storage and Retrieval (Florida STORET) database (2017 and earlier). WIN and Florida STORET are the source of much of the data displayed on the Water Atlas websites.



Caveats and Limitations

The most recent information on impairment status can be found in the Verified, Delist, and Study lists that may be downloaded from the FDEP website.

You can download the most recent list of "Waters Not Attaining Standards", either as a shapefile or a data table, from the FDEP Open Data website: https://geodata.dep.state.fl.us/datasets/waters-not-attaining-standards-wnas

Before responsibility for assessment of Florida waterbodies was transferred to FDEP by EPA, the EPA developed a number of Total Maximum Daily Load (TMDL) documents for Florida waterbodies. Those TMDLs that have not been superseded by FDEP TMDLS are still in effect; links to these are provided.