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Statewide Biennial Assessment

Implementation of a Statewide Biennial Assessment
(February 18, 2021)

The Department of Environmental Protection (department) is charged with using the best information available to identify surface waterbodies and waterbody segments that do not meet Florida’s water quality standards and designated uses. The department has delineated surface water segments into waterbody identification assessment units (WBIDs), which are identified as “impaired” if they do not attain Florida’s water quality standards. Basin assessments are conducted pursuant to section 403.067, Florida Statutes, consistent with the federal Clean Water Act. Impairment determinations enable the department and local stakeholders to target restoration programs and activities.

The department is piloting a change to its approach for assessing waters under the Impaired Waters Rule (Chapter 62-303, Florida Administrative Code). Under the new process, all of the basins in Florida will be assessed every two years rather than over the current five-year basin cycle. Assessments will have the same data assessment period and evaluated with the applicable water quality criteria. The department will complete the assessment analysis using all available water quality data throughout Florida and will publish an updated statewide impaired waters list every two years. For more detailed information on the biennial assessment and implementation schedule, please see the Process Document and Frequently Asked Questions.

Why is the department proposing this change?

The new biennial assessment approach will provide Floridians with a more up-to-date picture of Florida's overall water quality conditions. Stakeholders across the state will have current, actionable information that will promote more effective and timely water quality restoration.  

What will Statewide Biennial Assessment produce?

With the new biennial assessment, the impaired waters lists will include waters statewide, not just from a subset of basins. The Verified List and Study List include waterbodies and water segments that have been determined not to meet water quality standards. These waters are submitted to EPA as additions to the federal 303(d) list.

Waterbodies and water segments on the Delist List include those waters that are proposed for removal from the Verified List. Waterbodies and water segments on the Study List Removals List include those waters proposed for removal from the Study List. These waters also are submitted to EPA for removal from the federal 303(d) list. There are several reasons for removal, such as: the waterbody is no longer impaired; a Total Maximum Daily Load (TMDL) has been completed, triggering restoration activities; the impairment is due to a natural condition; the parameter was verified as impaired in the previous assessment due to a flaw in the original analysis; or corrections have been made to the waterbody type or class.  

Waterbodies identified on the State’s Verified List of Impaired Waters will be scheduled for TMDL development. A TMDL is a scientific determination of the maximum amount of a given pollutant that a surface water can absorb and still meet the water quality standards that protect human health and aquatic life. It is a precursor to the department’s development of a Basin Management Action Plan, and it also serves to guide the implementation of other restoration programs and projects.

Last Modified:
March 26, 2024 - 3:16pm

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