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12.0 Glossary
Topography: The physical shape of the ground surface. Configuration of a surface, including
its relief and the position of natural and man-made features.
Topple: A topple is a forward rotation of a mass of soil or rock out of a steep slope at a hinge
or pivot point below the center of gravity of the displaced mass. Topples usually involve the
overturn of interacting columns or blocks at or near a vertical face and may lead to falls or
slides of the displaced mass. Movement of material during a topple ranges from extremely
slow to extremely rapid.
Topsoil: The upper layer of soil, usually the top 2 to 8 inches.
Total Dissolved Solids (TDS): A quantitative measure of the residual minerals dissolved in
water that remains after evaporation of a solution. Usually expressed in milligrams per liter
or parts per million.
Total Maximum Daily Load (TMDL): An estimate of the total quantity of pollutants (from
all sources: point, non-point, and natural) that may be allowed into waters without exceeding
applicable water quality criteria.
Total Organic Gases (TOG): Gaseous organic compounds, including reactive organic gases
and the relatively unreactive organic gases such as methane.
Total Suspended Particulate (TSP): Particles of solid or liquid matter−such as soot, dust,
aerosols, fumes, and mist−up to approximately 30 microns in size.
Townhouse; Townhome: A one-family dwelling in a row of at least three such units in
which each unit has its own front and rear access to the outside, no unit is located over
another unit, and each unit is separated from any other unit by one or more common and
fire-resistant walls. Townhouses usually have separate utilities; however, in some
condominium situations, common areas are serviced by utilities purchased by a
homeowners association on behalf of all townhouse members of the association.
Toxic Air Contaminant (TACs): Airborne chemical compounds determined by the U.S.
Environmental Protection Agency (USEPA) and the California Environmental Protection
Agency (CalEPA), including the Office of Environmental Health Hazard Assessment and the
California Air Resources Board, to pose a present or potential threat to public health. Air
pollutants (excluding ozone, carbon monoxide, PM10, sulfur dioxide, and nitrogen dioxide)
that may reasonably be anticipated to cause cancer, developmental effects, reproductive
dysfunctions, neurological disorders, heritable gene mutations, or other serious or
irreversible acute or chronic health effects in humans. Toxic air pollutants are considered
under a different regulatory process (California Health and Safety Code, Sections 39650
et seq.) than pollutants subject to California Ambient Air Quality Standards. Health effects to
TACs may occur at extremely low levels, and it is typically difficult to identify levels
of exposure which do not produce adverse health effects.
Traffic Calming: The process of designing streets or adding design elements to tame fast
traffic and address unsafe traffic conditions. Design elements include, for example, speed
humps, narrowed streets, added traffic circle.
R:\Projects\PAS\CEN\000306\Draft EIR\12.0_Glossary-051017.docx 12-81 Centennial Project
Draft EIR
