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Tail Water: The runoff of irrigation water from the lower end of an irrigated field.

Tailings:
Residue of raw material or waste separated out during the processing of crops or mineral ores.

Tailpipe Standards: Emissions limitations applicable to mobile source engine exhausts.

Take-Out Point:
The metering points at which a metered entity takes delivery of energy.

Tampering:
Adjusting, negating, or removing pollution control equipment on a motor vehicle.

Tar Sands: Sedimentary rocks containing heavy oil that cannot be extracted by conventional petroleum recovery methods.

Tariff: A document, approved by the responsible regulatory agency, listing the terms and conditions, including a schedule of prices, under which utility services will be provided.

Task Lighting (Task-Oriented Lighting):
Lighting designed specifically to illuminate one or more task locations, and generally confined to those locations.

Technical Assistance Grant (TAG):
As part of the Superfund program, Technical Assistance Grants of up to $50,000 are provided to citizens' groups to obtain assistance in interpreting information related to clean-ups at Superfund sites or those proposed for the National Priorities List. Grants are used by such groups to hire technical advisors to help them understand the site-related technical information for the duration of response activities.

Technical-Grade Active Ingredient (TGA):
A pesticide chemical in pure form as it is manufactured prior to being formulated into an end-use product (e.g. wettable powders, granules, emulsifiable concentrates). Registered manufactured products composed of such chemicals are known as Technical Grade Products.

Technology-Based Limitations:
Industry-specific effluent limitations based on best available preventive technology applied to a discharge when it will not cause a violation of water quality standards at low stream flows. Usually applied to discharges into large rivers.

Technology-Based Standards:
Industry-specific effluent limitations applicable to direct and indirect sources which are developed on a category-by-category basis using statutory factors, not including water-quality effects.

Temperature:
Degree of hotness or coldness measured on one of the several arbitrary scales based on some observable phenomenon (such as the expansion).

Teratogen:
A substance capable of causing birth defects.

Teratogenesis:
The introduction of nonhereditary birth defects in a developing fetus by exogenous factors such as physical or chemical agents acting in the womb to interfere with normal embryonic development.

Terracing: Dikes built along the contour of sloping farm land that holds runoff and sediment to reduce erosion.

Tertiary Amyl Methyl Ether (TAME): Another oxygenate that can be used in reformulated gasoline. It is an ether based on reactive C5 olefins and methanol.

Tertiary Treatment:
Advanced cleaning of wastewater that goes beyond the secondary or biological stage, removing nutrients such as phosphorus, nitrogen, and most BOD and suspended solids.

The Electrical Grid: Continuing the water analogy, envision the electrical grid as a big pressurized water system with hundreds of pumps (generators) pumping water into the system through long pipes (transmission lines), and literally millions of customers sucking water out through smaller straws (utility distribution systems). There are hundreds of places (substations) where valves and adapters (switches and transformers) are used to break the large volumes of water down into smaller units under less pressure for delivery through the straws. The ISO’s job is to make sure that in the high-pressure system, the water pressure (voltage) and the RPMs of all the pumps (frequency) remain constant, even though inflow and outflow (measured in wattage) are both changing minute by minute.

Theoretical Maximum Residue Contribution:
The theoretical maximum amount of a pesticide in the daily diet of an average person. It assumes that the diet is composed of all food items for which there are tolerance-level residues of the pesticide. The TMRC is expressed as milligrams of pesticide/kilograms of body weight/day.

Therapeutic Index:
The ratio of the dose required to produce toxic or lethal effects to the dose required to produce the non-adverse or therapeutic response.

Therm: One hundred thousand (100,000) British thermal units (1 therm = 100,000 Btu).

Thermal Break (Thermal Barrier):
An element of low heat conductivity placed in such a way as to reduce or prevent the flow of heat. Some metal framed windows are designed with thermal breaks to improve their overall thermal performance.

Thermal Efficiency:
Quantity of heat produced in relation to fuel input.

Thermal (Energy) Storage:
A technology that lowers the amount of electricity needed for comfort conditioning during utility peak load periods. A building’s thermal energy storage system might, for example, use off-peak power to make ice or to chill water at night, later using the ice or chilled water in a power saving process for cooling during the day.

Thermal Mass: A material used to store heat, thereby slowing the temperature variation within a space. Typical thermal mass materials include concrete, brick, masonry, tile and mortar, water, and rock or other materials with high heat capacity.

Thermal Pollution:
Discharge of heated water from industrial processes that can kill or injure aquatic organisms.

Thermal Power Plant:
Any stationary or floating electrical generating facility using any source of thermal energy, with a generating capacity of 50 megawatts or more, and any facilities appurtenant thereto. Exploratory, development and production wells, resource transmission lines, and other related facilities used in connection with a geothermal exploratory project or a geothermal field development project are not appurtenant facilities for the purposes of this division. The thermal power plant does not include any wind, hydroelectric, or solar photovoltaic electrical generating facility.

Thermal Stratification:
The formation of layers of different temperatures in a lake or reservoir.

Thermal System Insulation (TSI):
Asbestos-containing material applied to pipes, fittings, boilers, breeching, tanks, ducts, or other interior structural components to prevent heat loss or gain or water condensation.

Thermal Treatment:
Use of elevated temperatures to treat hazardous wastes.

Thermally Enhanced Oil Recovery (TEOR):
Injection of steam to increase the amount of petroleum that may be recovered from a well.

Thermocline:
The middle layer of a thermally stratified lake or reservoir. In this layer, there is a rapid decrease in temperatures in a lake or reservoir.

Thermodynamics: A study of the transformation of energy into other manifested forms and of their practical applications. The three laws of thermodynamics are:

1. Law of Conservation of Energy -- energy may be transformed in an isolated system, but its total is constant

2. Heat cannot be changed directly into work at constant temperature by a cyclic process

3. Heat capacity and entropy of every crystalline solid becomes zero at absolute zero (0 degrees Kelvin)

Thermostat: An automatic control device designed to be responsive to temperature and typically used to maintain set temperatures by cycling the HVAC system.

Thermostat, Setback:
A device, containing a clock mechanism, which can automatically change the inside temperature maintained by the HVAC system according to a preset schedule. The heating or cooling requirements can be reduced when a building is unoccupied or when occupants are asleep.

Threshold: The lowest dose of a chemical at which a specified measurable effect is observed and below which it is not observed.

Threshold: The dose or exposure level below which a significant adverse effect is not expected.

Threshold Level:
Time-weighted average pollutant concentration values, exposure beyond which is likely to adversely affect human health.

Threshold Limit Value (TLV):
The concentration of an airborne substance to which an average person can be repeatedly exposed without adverse effects. TLVs may be expressed in three ways: (1) TLV-TWA--Time-weighted average, based on an allowable exposure averaged over a normal 8-hour workday or 40-hour work- week; (2) TLV-STEL--Short-term exposure limit or maximum concentration for a brief specified period of time, depending on a specific chemical (TWA must still be met); and (3) TLV-C--Ceiling Exposure Limit or maximum exposure concentration not to be exceeded under any circumstances. (TWA must still be met.)

Threshold Planning Quantity: A quantity designated for each chemical on the list of extremely hazardous substances that triggers the notification by facilities to the State Emergency Response Commission that such facilities are subject to emergency planning requirements under SARA Title III.

Tropic Levels: A functional classification of species that is based on feeding relationships (e.g. generally aquatic and terrestrial green plants comprise the first tropic level, and herbivores comprise the second.)

Tidal Marsh: Low, flat marshlands traversed by channels and tidal hollows, subject to tidal inundation; normally, the only vegetation present is salt-tolerant bushes and grasses.

Tidal Power:
Energy obtained by using the motion of the tides to run water turbines that drive electric generators.

Tillage: Plowing, seedbed preparation, and cultivation practices.

Time-Of-Use Meter: A measuring device that records the times during which a customer uses various amounts of electricity. This type of meter is used for customers who pay time-of-use rates.

Time-Of-Use Rates: Electricity prices that vary depending on the time periods in which the energy is consumed. In a time-of- use rate structure, higher prices are charged during utility peak-load times. Such rates can provide an incentive for consumers to curb power use during peak times.

Time-Of-Use (TOU) Rates:
The pricing of electricity based on the estimated cost of electricity during a particular time block. Time-of-use rates are usually divided into three or four-time blocks per twenty-four hour period (on-peak, mid-peak, off-peak and sometimes super off-peak) and by seasons of the year (summer and winter). Real-time pricing differs from TOU rates in that it is based on actual (as opposed to forecasted) prices which may fluctuate many times a day and are weather-sensitive, rather than varying with a fixed schedule.

Time-weighted Average (TWA): In air sampling, the average air concentration of contaminants during a given period.

Tipping Fee:
A fee for unloading or dumping waste at a landfill, transfer station, waste-to-energy facility, or recycling facility (also see Disposal Fee).

Tipping Floor: Unloading area for vehicles that are delivering MSW to a waste-to-energy plant.

Tire Processor:
The intermediate operating facility where recovered tires are processed in preparation for recycling.

Tires: As used in recycling, passenger car and truck tires (excludes airplane, bus, motorcycle and special service military, agricultural, off-the-road and-slow speed industrial tires). Car and truck tires are recycled into rubber products such as trash cans, storage containers, rubberized asphalt or used whole for playground and reef construction.

Tolerance Petition:
A formal request to establish a new tolerance or modify an existing one.

Tolerances:
Permissible residue levels for pesticides in raw agricultural produce and processed foods. Whenever a pesticide is registered for use on a food or a feed crop, a tolerance (or exemption from the tolerance requirement) must be established. EPA establishes the tolerance levels, which are enforced by the Food and Drug Administration and the Department of Agriculture.

Ton Of Cooling: A useful cooling effect equal to 12,000 Btu hours.

Tonnage: The amount of waste that a landfill accepts, usually expressed in tons per month. The rate at which a landfill accepts waste is limited by the landfill's permit.

Topography:
The physical features of a surface area including relative elevations and the position of natural and man-made (anthropogenic) features.

Total Dissolved Phosphorous:
The total phosphorous content of all material that will pass through a filter, which is determined as orthophosphate without prior digestion or hydrolysis. Also called soluble P or ortho-P.

Total Dissolved Solids (TDS):
All material that passes the standard glass river filter; now called total filterable residue. The term is used to reflect salinity.

Total Efficiency:
Sum of the electrical and thermal efficiency in relation to the fuel consumed

Total Maximum Daily Load (TMDL):
A calculation of the highest amount of a pollutant that a water body can receive and safely meet water quality standards set by the state, territory, or authorized tribe.

Total Petroleum Hydrocarbons (TPH): Measure of the concentration or mass of petroleum hydrocarbon constituents present in a given amount of soil or water. The word "total" is a misnomer--few, if any, of the procedures for quantifying hydrocarbons, can measure all of them in a given sample. Volatile ones are usually lost in the process and not quantified and non-petroleum hydrocarbons sometimes appear in the analysis.

Total Recovered Petroleum Hydrocarbon:
A method for measuring petroleum hydrocarbons in samples of soil or water.

Total Suspended Particles (TSP):
A method of monitoring airborne particulate matter by total weight.

Total Suspended Solids (TSS):
A measure of the suspended solids in wastewater, effluent, or water bodies, determined by tests for "total suspended non-filterable solids".

Toxaphene: Chemical that causes adverse health effects in domestic water supplies and is toxic to fresh water and marine aquatic life.

Toxic Air Pollutant: Poisonous substances in the air that come from natural resources or manmade sources and can harm the environment or human health.

Toxic Chemical:
Any chemical listed in EPA rules as "Toxic Chemicals Subject to Section 313 of the Emergency Planning and Community Right-to-Know Act of 1986."

Toxic Chemical Release Form: Information form required of facilities that manufacture, process, or use (in quantities above a specific amount) chemicals listed under SARA Title III.

Toxic Chemical Use Substitution:
Replacing toxic chemicals with less harmful chemicals in industrial processes.

Toxic Cloud:
Airborne plume of gasses, vapors, fumes, or aerosols containing toxic materials.

Toxic Concentration:
The concentration at which a substance produces a toxic effect.

Toxic Dose: The dose level at which a substance produces a toxic effect.

Toxic Pollutants:
Materials that cause death, disease, or birth defects in organisms that ingest or absorb them. The quantities and exposures necessary to cause these effects can vary widely.

Toxic Release Inventory: Database of toxic releases in the United States compiled from SARA Title III Section 313 reports.

Toxic Substance: A chemical or mixture that may present an unreasonable risk of injury to health or the environment.

Toxic Waste: A waste that can produce injury if inhaled, swallowed, or absorbed through the skin.

Toxicant:
A harmful substance or agent that may injure an exposed organism.

Toxicity: The degree to which a substance or mixture of substances can harm humans or animals. Acute toxicity involves harmful effects in an organism through a single or short-term exposure. Chronic toxicity is the ability of a substance or mixture of substances to cause harmful effects over an extended period, usually upon repeated or continuous exposure sometimes lasting for the entire life of the exposed organism. Subchronic toxicity is the ability of the substance to cause effects for more than one year but less than the lifetime of the exposed organism.

Toxicity Assessment: Characterization of the toxicological properties and effects of a chemical, with special emphasis on the establishment of dose-response characteristics.

Toxicity Testing: Biological testing (usually with an invertebrate, fish, or small mammal) to determine the adverse effects of a compound or effluent.

Toxicological Profile: An examination, summary, and interpretation of a hazardous substance to determine levels of exposure and associated health effects.

Trading Day: The 24-hour period beginning at midnight and ending at the following midnight.

Transboundary Pollutants: Air pollution that travels from one jurisdiction to another, often crossing state or international boundaries. Also, applies to water pollution.

Transfer: The act of moving waste from a collection vehicle to a larger transport vehicle.

Transfer (Electric Utility): To move electric energy from one utility system to another over transmission lines.

Transfer Point: A designated point, often at the edge of a neighborhood, where small collection vehicles transfer waste to larger vehicles for transport to disposal sites.

Transfer Station: Facility where solid waste is transferred from collection vehicles to larger trucks or rail cars for longer distance transport.

Transformer: A device, which through electromagnetic induction but without the use of moving parts, transforms alternating or intermittent electric energy in one circuit into energy of similar type in another circuit, commonly with altered values of voltage and current.

Transient Water System: A non-community water system that does not serve 25 of the same non-residents per day for more than six months per year.

Transition Costs:
See Embedded Costs Exceeding Market Prices.

Transitional Low Emission Vehicle (TLEV):
A vehicle certified by the California Air Resources Board to have emissions from zero to 50,000 miles no higher than 0.125 grams/mile (g/mi) of non-methane organic gasses, 3.4 g/mi of carbon monoxide, and 0.4 g/mi of nitrogen oxides. Emissions from 50,000 to 100,000 miles may be slightly higher.

Transmission: Transporting bulk power over long distances.

Transmission-Dependent Utility:
A utility that relies on its neighboring utilities to transmit to it the power it buys from its suppliers. A utility without its own generation sources, dependent on another utility's transmission system to get its purchased power supplies.

Transmission Lines: Pipelines that transport raw water from its source to a water treatment plant, then to the distribution grid system.

Transmission Owner:
An entity that owns transmission facilities or has the firm contractual right to use transmission facilities.

Transmissivity:
The ability of an aquifer to transmit water.

Transmittance: The time rate of heat flow per unit area under steady conditions from the air (or other fluid) on the warm side of a barrier to the air (or fluid) on the cool side, per unit temperature difference between the two sides.

Transmitting Utility (TRANSCO):
This is a regulated entity which owns and may construct and maintain, wires used to transmit wholesale power. It may or may not handle the power dispatch and coordination functions. It is regulated to provide non-discriminatory connections, comparable service, and cost recovery. According to EP Act, any electric utility, qualifying cogeneration facility, qualifying small power production facility, or Federal power marketing agency which owns or operates electric power transmission facilities which are used for the sale of electric energy at wholesale.

Transpiration:
The process by which water vapor is lost to the atmosphere from living plants. The term can also be applied to the quantity of water thus dissipated.

Transportation Control Measures (TCMs):
Steps were taken by a locality to reduce vehicular emission and improve air quality by reducing or changing the flow of traffic; e.g. bus and HOV lanes, carpooling and other forms of ride-sharing, public transit, bicycle lanes.

Transporter:
Hauling firm that picks up properly packaged and labeled hazardous waste from generators and transports it to designated facilities for treatment, storage, or disposal. Transporters are subject to EPA and DOT hazardous waste regulations.

Trash: Material considered worthless or offensive that is thrown away. Generally defined as a dry waste material, but in common usage, it is a synonym for garbage, rubbish, or refuse.

Trash-to-Energy Plan: Burning trash to produce energy.

Treatability Studies:
Tests of potential cleanup technologies conducted in a laboratory.

Treated Regulated Medical Waste: Medical waste treated to substantially reduce or eliminate its pathogenicity, but that has not yet been destroyed.

Treated Wastewater:
Wastewater that has been subjected to one or more physical, chemical, and biological processes to reduce its potential of being a health hazard.

Treatment:
(1) Any method, technique, or process designed to remove solids and/or pollutants from solid waste, waste-streams, effluents, and air emissions. (2) Methods used to change the biological character or composition of any regulated medical waste so as to substantially reduce or eliminate its potential for causing disease.

Treatment Plant:
A structure built to treat wastewater before discharging it into the environment.

Treatment, Storage, and Disposal Facility:
Site where a hazardous substance is treated, stored, or disposed of. TSD facilities are regulated by EPA and states under RCRA.

Tremie: Device used to place concrete or grout under water.

Trial Burn: An incinerator test in which emissions are monitored for the presence of specific organic compounds, particulates, and hydrogen chloride.

Trichloroethylene (TCE):
A stable, low boiling-point colorless liquid, toxic if inhaled. Used as a solvent or metal degreasing agent, and in other industrial applications.

Trickle Irrigation:
Method in which water drips to the soil from perforated tubes or emitters.

Trickling Filter:
A coarse treatment system in which wastewater is trickled over a bed of stones or other material covered with bacteria that break down the organic waste and produce clean water.

Trihalomethane (THM):
One of a family of organic compounds named as derivative of methane. THMs are generally by-products of chlorination of drinking water that contains organic material.

Troposphere:
The layer of the atmosphere closest to the earth's surface.

Truck Scales or Weighbridge: A platform used for weighing vehicles.

Trust Fund (CERCLA):
A fund set up under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) to help pay for the cleanup of hazardous waste sites and for legal action to force those responsible for the sites to clean them up.

Tube Settler:
Device using bundles of tubes to let solids in water settle to the bottom for removal by conventional sludge collection means; sometimes used in sedimentation basins and clarifiers to improve particle removal.

Tuberculation: Development or formation of small mounds of corrosion products on the inside of the iron pipe. These tubercules roughen the inside of the pipe, increasing its resistance to water flow.

Tundra: A type of treeless ecosystem dominated by lichens, mosses, grasses, and woody plants. Tundra is found at high latitudes (arctic tundra) and high altitudes (alpine tundra). Arctic tundra is underlain by permafrost and is usually water saturated.

Turbidimeter: A device that measures the cloudiness of suspended solids in a liquid; a measure of the quantity of suspended solids.

Turbidity: 1. Haziness in the air caused by the presence of particles and pollutants. 2. A cloudy condition in water due to suspended silt or organic matter.

Turbine Generator:
A device that uses steam, heated gasses, water flow or the wind to cause spinning motion that activates electromagnetic forces and generates electricity.