Environmental Terms Glossary
T
Tarp
A sheet of waterproof canvas or other material used to cover and protect materials, equipment or vehicles.
TC
Toxicity Characteristic
TCDD
Tetrachlorodibenzodioxin. A TCDD associated with the manufacturer of 2,4,5-T (Silvex) and occurring as a thermal degradation product of chlorinated benzenes.
TCLP
Toxicity Characteristic Leaching Procedure
TDS
Total Dissolved Solids
Threshold
The intensity or concentration below which a stimulus or substance produces a specified effect.
TI
Transport Index. Applicable to radioactive materials (see Title 49 CFR 173.403(bb).
Time Weighted Composite
A composite sample consisting of a mixture of equal volume aliquots collected at a constant time interval.
Time, Distance, Shielding
Gamma rays are the most dangerous type of radiation and are the most difficult to protect oneself from. The only way is through time (shorten the exposure), distance (increase the distance between the source and the person), and shielding or mass (increase the mass between the source and the person - i.e., earth or lead).
TLV
Threshold Limit Value (ACGIH)
Total Dissolved Solids
The concentration of minerals in water.
Total Suspended Solids (TSS)
A measure of the suspend solids in wastewater, effluent, or water bodies, determined by using tests for total suspended non-filterable solids.
Totally Enclosed Manner
Any manner of usage that will result in no exposure of human beings or the environment to any concentration of PCBs. (TSCA Usage).
Toxic Pollutants
Any pollutant listed as toxic under Section 501(a)(1) or, in the case of "sludge use or disposal practices," any pollutant identified in regulations implementing Section 405(d) of the CWA; toxics are injurious to human health or animals.
Toxicity
The harmfulness of a contaminant.
Toxicity Characteristic Leaching Procedure
A laboratory method used to determine the potential for solid contaminants or contaminants attached to soil particles to become dissolved into water.
Treatment
The act of applying a procedure or chemicals to a substance to remove undesirable pollutants.
Treatment, Storage, and Disposal Facility (TSD)
Any building, structure, or installation where a hazardous substance is or has been treated, stored, or disposed.
Tributary
A river or stream that flows into a larger river or stream.
TSCA
Toxic Substances Control Act. Federal law authorizing EPA to gather information on chemical risks.
- TSD
Treatment, Storage and Disposal
TSP
Total Suspended Particulates
TSS
Total Suspended Solids
TTU
Transportable Treatment Unit
TWA
Time-Weighted Average
U
UEL
Upper Explosive Limits. The highest concentration of the material in air that can be detonated by spark, shock, fire, etc.
UFL
Upper Flammable Level. The highest concentration of the material in air that will support combustion.
UIC
Underground Injection Control
UMTCA
Uranium Mill Tailings Control Act (1978)
UN Number
United Nations Identifications Number. When UN precedes a four-digit number, it indicates this identification number is used internationally to identify a hazardous material.
Unsaturated Hydrocarbons
A hydrocarbon in which not all of the valence bonds are taken up by hydrogen atoms and the carbons bond with themselves with double or triple bonds. These materials are more unstable than the saturated hydrocarbons and quite often pose a greater risk of fire or explosion to the responder.
Unsaturation
The state in which not all of the available valence bonds of an atom are satisfied, usually resulting in the formation of double or triple bonds. These compounds are less stable than saturated compounds.
Upset
Any exceptional incident in which there is unintentional and temporary noncompliance with the numeric effluent limitations of Part V of this permit because of factors beyond the reasonable control of the permittee. An upset does not include noncompliance to the extent caused by operational error, improperly designed treatment facilities, inadequate treatment facilities, lack of preventive maintenance, or careless or improper operation.
USPCI
U.S. Pollution Control Inc.
UST
Underground Storage Tanks RCRA regulated tank and connected piping with 10 or more percent of its volume underground; used to store petroleum products or CERCLA regulated hazardous chemicals.
USWAG
Utility Solid Waste Activities Group
V
Vapor
An air dispersion of molecules of a substance that is liquid or solid in its normal physical state, at standard temperature and pressure.
Vapor Density
The ratio of the density of a gas to the density of air. Products with a vapor density less than 1 will tend to rise and those with a vapor density greater than 1 will tend to sink in air.
Vapor Pressure
The pressure exerted by a vapor when it is in equilibrium with its liquid. A characteristic property of a liquid that tells us the amount of vapors that are going to be given off at a certain temperature. Usually measured at room temperature (68 degrees F) and even in mm of Hg (mercury).
VE
Visible Emission
Vehicle Maintenance Area (VM)
Onsite location or area where transportation or transportation related vehicles are repaired, serviced, fueled, or otherwise maintained.
Vibration
This value is in relation to vibrations caused from wind, mechanical equipment, road vehicles, trains, etc. These forces tend to create vibration which accelerate fiber release.
Viscosity
The internal resistance to flow of a product. Often used to define the thickness of a liquid or sludge.
VMT
Vehicle Miles Traveled
VOC
Volatile Organic Compound. Any of a group of organic compounds that volatilize (vaporize) at normal temperatures and pressures.
Volatile Organic Compound (VOC)
Any of a group of organic compounds that volatilize (vaporize) at normal temperatures and pressures.
Volatility
The tendency of a liquid or solid to pass into the vapor state. Volatile liquids readily give off vapors and have low boiling points such as Hexane. Non volatile liquids give off little or no vapors at room temperature such as poly-chlorinated byphenyls (PCS's).
W
Waste
Unwanted materials left over from a manufacturing, industrial or other process or activity.
Waste Characterization
The act of determining what a waste material contains. May include laboratory tests or other analysis.
Waste Minimization
Any source reduction or recycling activity undertaken by a generator that results in either (1) the reduction of total volume or quantity of waste or (2) the reduction of toxicity of hazardous waste, or both so long as such as reduction is consistent with the goal of minimizing present and future threats to human health and the environment.
Waste Pile
Any noncontainerized accumulation of a solid, nonflowing waste that is used for treatment or storage.
Waste Stream
A separate or combined source of waste resulting from a plant's process.
Wastes
Any liquid or solid material that is no longer suitable for its original intended purpose and requires disposal if not recycled.
Wastewater
Process water contaminated to such an extent that it cannot be reused without some repurification.
Wastewater Treatment Plant (WWTP)
A plant that reduces the harmful and unstable elements in wastewater so they can be disposed of without impairing other essential water uses.
Water Miscible
The ability of a substance to dissolve in water without separating into two phases.
Water Reactivity
The material's ability to react with water. Water reactive materials react with water or humid air, causing some type of release in the form of heat, fire or the generation of some type of gas.
Water Solubility
The ability of a substance to blend uniformly with water, usually given by simply stating "no," "very slight," "slight," and "yes."
Water Table
The depth or level below which the ground is saturated with water.
Waters of the United States
Waters under the general protection and control of the United States. These include:
- All waters, which are currently used, were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters which are subject to the ebb and flow of the tide;
- All interstate waters, including interstate "wetlands";
- All other waters such as intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, "wetlands", sloughs, prairie potholes, wet meadows, plays lakes, or natural ponds, the use, degradation, or destruction of which would affect or could affect interstate or foreign commerce including any such waters:
- Which are or could be used by interstate or foreign travelers for recreational or other purposes;
- From which fish or shellfish are or could be taken and sold in interstate or foreign commerce; or
- Which are used or could be used for industrial purposes by industries in interstate commerce;
- All impoundments of waters otherwise defined as waters of the United States under this definition;
- Tributaries of waters identified in paragraphs (a) through (d) of this definition;
- The territorial sea; and
- "Wetlands" adjacent to waters (other than waters that are themselves wetlands) identified in paragraphs (a) through (f) of this definition.
Waterway
A channel for the passage or flow of water.
Well Casing
The slotted pipe (usually plastic or stainless steel) which is installed in a soil boring to make a groundwater well.
Wellhead
The point at which a well (whether or not cased) reaches the surface of the land.
Wetlands
An area that is regularly saturated by surface or ground water and subsequently is characterized by a prevalence of vegetation that is adapted for life in saturated soil conditions.
WQA
Water Quality Act of 1987
WQMP
Water Quality Management Plan
WSRA
Wild and Scenic Rivers Act (1968)
WWTP
Waste Water Treatment Plant. A plant that reduces the harmful and unstable elements in wastewater so they can be disposed of without impairing other essential water uses.