is a Total Maximum Daily Load (TMDL)?
Daily Loads are quantitative analyses of water bodies
where one or more water quality standards are not being
met, and are aimed at identifying the management
strategies necessary to attain those water quality
standards. In essence, TMDLs describe the amount of each
pollutant a water body can receive without violating
standards, and are characterized as the sum of wasteload
allocations, load allocations, and a margin of safety to
account for uncertainties. Wasteload allocations are
pollutant loads attributable to existing and future point
sources, such as discharges from industry and sewage
facilities. Load allocations are pollutant loads
attributable to existing and future nonpoint sources and
natural background. Nonpoint sources include runoff from
farms, forests, urban areas, and natural sources, such as
decaying organic matter and nutrients in soil.
take into account the water quality of an entire water
body or watershed and assess all the pollutant loadings
into that watershed, rather than simply considering
whether each individual discharge meets its permit
requirements. The management strategies that emerge from
the TMDL process may encompass everything from
traditional regulatory measures, agricultural best
management practices and other pollution prevention
measures, land acquisition, infrastructure funding,
pollutant trading, and the like. They also will include
an overall monitoring plan to test their effectiveness.
are TMDLs developed?
For the past
twenty-five years, point source discharges have been
regulated under the Clean Water Act (CWA).
Over time, it has become clear in many instances that
every individual discharge into a water body may meet
effluent discharge requirements and yet that water body
may still fail to meet the standards defining good water
quality. This circumstance has proved true even as the
limits on point source discharges have become more and
more stringent, especially in Florida. There clearly
are other sources of pollution for which existing control
measures are simply not adequate. These sources are
associated with diffuse runoff and habitat destruction,
and originate in both urban and rural areas.
EPA requires states to set priorities for cleaning up
impaired waters by establishing a TMDL for each one.
Under the authority of section 303(d) of the CWA, EPA
requires that TMDLs be developed where technology-based
effluent limitations or other legally required pollution
control mechanisms are not stringent enough to protect
water quality. Florida has hundreds of impaired
water bodies or water body segments that likely will have
to be addressed through the development and
implementation of TMDLs.
development of Total Maximum Daily Loads (TMDLs) will
take place in the context of
99-223, Laws of Florida, which details the process
for listing impaired waters, determining which waters
will be subjected to TMDL calculations, adopting by rule
those calculations and associated allocations of
pollutant loadings, and implementing the management
strategies designed to reduce the loadings and enable the
water body to meet water quality standards.
are TMDLs Established?
As noted, TMDLs
are established for waters that fail to meet water
quality standards, and characterize how much of each
pollutant the water body can assimilate without violating
those standards. The DEP considers future growth and
development to the extent possible in establishing a
TMDL, and accounts for the pollutant inputs from all
sources, including discharges from industrial plants and
sewage treatment facilities, runoff from farms, forests
and urban areas, and natural sources.
deriving a TMDL and subsequently setting forth the
mechanisms that may be employed to enable the water body
to meet standards, the DEP must balance the quantities of
pollutants from all sources so that the total amount does
not exceed the limits necessary to maintain water
quality. Through these assessments, DEP can better
determine permit effluent limits, best management
practices, pollution prevention strategies, and other
resource management activities necessary to ensure that
waters are suitable for fishing, drinking, recreation,
and aquatic life.
a TMDL approach for water bodies does not replace
existing water quality control programs or standard
treatment technologies. It provides a framework for
evaluating all possible water quality control efforts and
promotes closer coordination of local, state, and federal
efforts to better guarantee that we collectively meet
water quality goals.
is the 303(d) list?
303(d) of the Clean Water Act, every two
years each state must identify water bodies that do
not meet water quality standards. These water bodies
are "water quality-limited" estuaries, lakes,
and streams that fall short of surface water quality
standards, and that are not expected to improve within
the subsequent two years. Florida's water quality
standards are designed to ensure that our waters can be
used for their designated purposes, such as swimming,
drinking, industrial and agricultural uses, and wildlife
list identifies hundreds of "impaired"
water segments, with the four most common water quality
concerns being coliforms, nutrients, oxygen demanding
substances, and turbidity. These water segments are
candidates for more detailed assessments of water quality
and, where necessary, the development and implementation
is the Florida 303(d) list developed?
303(d) list is developed based on the Florida Water
Quality Assessment [305(b) report]. Section 305(b)
of the CWA requires states to report biennially to the
EPA on their water quality. The 305(b) report describes
the existing programs to protect the quality of Florida's
surface waters, ground water, and wetlands. In the 305(b)
report, water quality is evaluated using biological data,
chemistry data from the federal water quality database
(STORET), violations of Florida's water quality
standards, mercury fish consumption advisories,
qualitative nonpoint source assessments, and other
information solicited through public workshops. The
information in the report is reviewed and water bodies
are placed on the 303(d) list of impaired waters based on
specific criteria designed to identify the highest
priority water bodies in need of restoration based on the
best available data.
more information, send e-mail to
Greg DeAngelo (Gregory.DeAngelo@dep.state.fl.us)
Water Quality Evaluation & TMDL Program
2600 Blair Stone Road - Mail Station 3555
Tallahassee, FL, 32399-2400
Phone: (850) 245-7609