Environmental Engineering Reference
In-Depth Information
Environmental Protection Agency (EPA) for regulating point
sources such as sewage plants or industrial facilities like man-
ufacturing, mining, and oil and gas extraction. Point sources
may not discharge pollutants to surface waters without a per-
mit from EPA, in partnership with state environmental agen-
cies. The permit describes what and how much is allowed to be
discharged. EPA requires technology-based standards, which
are developed for each category of dischargers based on pol-
lution control technologies, without regard to the conditions
of a particular water body. The idea was to establish a basic
standard for all facilities in a category, using the best-available
technology. Water bodies that do not meet water quality stan-
dards with technology-based controls alone are placed on a
list of water bodies not meeting standards. If water quality
still remains impaired (probably because many sources dis-
charge into the same waterbody), then the permit agency (state
or EPA) may add water quality-based limitations to the permit.
These limitations are more stringent and require the facility to
upgrade and install additional controls. They must develop a
total maximum daily load (TMDL), which is a calculation of
the maximum amount of a pollutant that a water body can
receive and still meet water quality standards. The TMDL
is determined after study of the water body and the pollut-
ant sources contributing to the noncompliance. Water qual-
ity standards include designated uses (the best being fishable
and swimmable), water quality criteria, and antidegradation
policy. Water quality criteria can be numeric levels of specific
pollutants. A narrative criterion serves as the basis to limit tox-
icity of waste to aquatic species. A biological criterion is based
on the aquatic community—the number and types of species
present in a water body. A nutrient criterion protects against
nutrient overenrichment, and a sediment criterion describes
conditions of contaminated and uncontaminated sediments in
order to avoid undesirable effects.
After passage of the Clean Water Act, communities
upgraded their sewage treatment plants, factories upgraded
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