Middle St. Johns - Florida Department of Environmental Protection

Water Quality Assessment Report: Middle St. Johns 245
Appendix E: Methodology for Determining Impairment Based
on the Impaired Surface Waters Rule
The Impaired Surface Waters Rule
To identify impaired waters in each of the state’s river basins, the Department
evaluates water quality data using the science-based methodology in the Identification of
Impaired Surface Waters Rule (Rule 62-303, F.A.C.). The rule establishes specific
criteria and thresholds for impairment, in addition to data sufficiency and data quality
requirements. The methodology described in the rule is based on a statistical approach
designed to provide greater confidence that the outcome of the water quality assessment
is correct. The complete text of the Impaired Surface Waters Rule is available at
http://www.dep.state.fl.us/water/tmdl/docs/AmendedIWR.pdf.
As part of the watershed management approach, for each river basin in the state the
Department will follow the methodology in Section 62-303.300, F.A.C., to develop a
Planning List of potentially impaired waters to be assessed under Subsections 403.067(2)
and (3), F.S. The methodology for developing the Planning List includes an evaluation
of aquatic life use support, primary contact and recreational use support, fish shellfish
consumption use support, drinking water use support, and protection of human health.
Data older than ten years cannot be used to evaluate water quality criteria exceedances
for the Planning List. As required by Subsection 403.067(2), F.S., the Planning List will
not be used to administer or implement any regulatory program, and is submitted to the
EPA for informational purposes only.
After further assessment, using the methodology in Part III, Section 62-303.400,
F.A.C., the Department will determine if waters on the Planning List are, in fact,
impaired and if the impairment is caused by pollutant discharges. These waters are
placed on a Verified List. The criteria for the Verified List are more stringent than those
for the Planning List. Data older than five years should not be used to verify impairment.
The Verified List will be adopted by Secretarial Order and forwarded to the EPA for
approval as Florida’s Section 303(d) list of impaired waters. The Department will
develop TMDLs for these waters under Subsection 403.067(4), F.S.
Attainment of Designated Use(s)
While the designated uses of a given waterbody are established using the surface
water quality classification system described previously, it is important to note that the
EPA uses slightly different terminology in its description of designated uses. Because the
Department is required to provide use attainment status for both the state’s 305(b) report
and the state’s 303(d) list of impaired waters, the Department uses EPA terminology
when assessing waters for use attainment. The water quality evaluations and decision
processes for listing impaired waters that are defined in Florida’s Impaired Surface
Waters Rule are based on the following designated use attainment categories: