Total Maximum
Daily Load (TMDL)
The Clean
Water Act (CWA) requires states to protect the nation’s waters so that
they can be used for various designated purposes such as drinking water,
fishing, swimming, irrigation, or industrial use. Depending on the
designated use of a particular stream, river or lake, a water quality
standard is established. Logically, the water quality standards for
a river used as drinking water supply are more stringent than the standards
for a stream used primarily for irrigation or industrial use.
For each
pollutant that causes a water body to fail to meet water quality standards,
the state must conduct a Total Maximum Daily Load (TMDL) study. A TMDL
study identifies point and non-point sources of each pollutant that
fails to meet water quality standards. Water quality sampling and computer
modeling are then employed to determine how much each pollutant source
must reduce its contribution to assure that the water quality standard
is met. Rivers and streams may have several TMDLs, each one determining
the limit for a different pollutant.
Why
are TMDLs important to builders, developers and landowners?
- If your
construction site runoff enters a water body that has a TMDL, then,
in some states, you must consider the effects of your construction
site runoff on water quality before you can receive coverage under
the general stormwater permit.
- Some
states have adopted permit waivers for small construction sites (1
to less than five acres) that discharge to waters not covered by
a TMDL.
TMDL
State Program Tool
Use this tool to find out more about the TMDL program in your state and to
identify and locate impaired waters in your state. Use the pulldown or sensitive
map to select a state.
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Click
on a state's initials:
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