Drinking Water Regulations - The Drinking Water - page 37

Recharge zone —The area through which water enters a sole or principal
source aquifer.
Regulated substances— Substances regulated by the USEPA and that
cannot be present at levels above the MCL.
Significant hazard to public health —Any level of contaminant that causes
or may cause the aquifer to exceed any maximum contaminant level
set forth in any promulgated National Primary Drinking Water
Regulations at any point where the water may be used for drink-
ing purposes or which may otherwise adversely affect the health
of persons, or which may require a public water system to install
additional treatment to prevent such adverse effect.
Sole or principal source aquifer —An aquifer that supplies 50% or more of
the drinking water for an area.
Streamflow source zone —Upstream headwaters areas that drain into an
aquifer recharge zone.
Toxic pollutants —Pollutants that after discharge and upon exposure,
ingestion, inhalation, or assimilation into any organism will, on the
basis of the information available, cause death, disease, behavioral
abnormalities, cancer, genetic mutations, physiological malfunc-
tions, or physical deformations in such organisms or their offspring.
Treatment technique (TT) —A required process intended to reduce the
level of a substance in drinking water.
Turbidity —A measure of the cloudiness of water; turbidity is not nec-
essarily harmful but can interfere with the disinfection of drinking
water.
Unregulated monitored substances —Substances that are not regulated by
the USEPA but must be monitored so information about their pres-
ence in drinking water can be used to develop limits.
Vari ance —A document issued to water systems having technical and
financial difficulty meeting national primary drinking water regu-
lations; it postpones compliance when such a delay will not result
in an unreasonable risk to health.
Waters of the United States —(a) All waters that are currently used,
were used in the past, or may be susceptible to use in interstate
or foreign commerce, including all waters that are subject to the
ebb and flow of the tide; (b) all interstate waters, including inter-
state wetlands; (c) all other waters, such as interstate lakes, rivers,
streams, mudflats, sandflats, wetlands, sloughs, prairie potholes,
wet meadows, playa lakes, or natural ponds, the use, degradation,
or destruction of which would affect or could affect interstate or
foreign commerce.