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Ignitable: Capable of burning or causing a fire.

Imbalance Energy:
The real-time change in generation output or demand requested by the ISO to maintain reliability of the ISO-controlled grid. Sources of imbalance energy include regulation, spinning and non-spinning reserves, replacement reserve, and energy from other generating units that are able to respond to the ISO's request for more or less energy.

Imhoff Cone: A clear, cone-shaped container used to measure the volume of settleable solids in a specific volume of water.

Immiscibility: The inability of two or more substances or liquids to readily dissolve into one another, such as soil and water. Immiscibility The inability of two or more substances or liquids to readily dissolve into one another, such as soil and water.

Impermeable: Not easily penetrated. The property of a material or soil that does not allow, or allows only with great difficulty, the movement or passage of water.

Imports: Municipal solid waste and recyclables that have been transported to a state or locality for processing or final disposition (but that did not originate in that state or locality).

Imports (Electric Utility): Power capacity or energy obtained by one utility from others under purchase or exchange agreement.

Impoundment: A body of water or sludge confined by a dam, dike, floodgate, or other barrier.

In-Line Filtration: Pre-treatment method in which chemicals are mixed by the flowing water; commonly used in pressure filtration installations. Eliminates need for flocculation and sedimentation.

In Situ:
In its original place; unmoved unexcavated; remaining at the site or in the subsurface.

In-Situ Combustion: An experimental means of recovering hard-to-get petroleum by burning some of the oil in its natural underground reservoir. It is also called FIREFLOODING.

In-Situ Flushing:
Introduction of large volumes of water, at times supplemented with cleaning compounds, into soil, waste, or ground water to flush hazardous contaminants from a site.

In-Situ Gasification: Converting coal into synthetic gas at the place where the coal is found in nature.

In-Situ Oxidation:
Technology that oxidizes contaminants dissolved in ground water, converting them into insoluble compounds.

In-Situ Stripping:
Treatment system that removes or "strips" volatile organic compounds from contaminated ground or surface water by forcing an airstream through the water and causing the compounds to evaporate.

In-Situ Vitrification:
Technology that treats contaminated soil in place at extremely high temperatures, at or more than 3000 degrees Fahrenheit.

In Vitro: Testing or action outside an organism (e.g. inside a test tube or culture dish.)

In Vivo: Testing or action inside an organism.

Incandescent Lamp: An electric lamp in which a filament is heated by an electric current until it emits visible light.

Incineration: A treatment technology involving destruction of waste by controlled burning at high temperatures; e.g., burning sludge to remove the water and reduce the remaining residues to a safe, non-burnable ash that can be disposed of safely on land, in some waters, or in underground locations.

A thermal waste treatment method involving combustion (the technology and temperature vary depending on the type of waste), and flue gas treatment. This technique yields three types of residue: bottom ash, fly ash and flue gas treatment residue. The heat generated by incineration is recovered at most facilities to produce energy (electricity or heat).

Incineration at Sea: Disposal of waste by burning at sea on specially-designed incinerator ships.

Incinerator: A furnace for burning waste under controlled conditions.

Incompatible Waste: A waste unsuitable for mixing with another waste or material because it may react to form a hazard.

Independent Power Producer (IPP):
An Independent Power Producer (IPP) generates power that is purchased by an electric utility at wholesale prices. The utility then resells this power to end-use customers. Although IPPs generate power, they are not franchised utilities, government agencies or QFs. IPPs usually do not own transmission lines to transmit the power that they generate.

Independent System Operator (ISO):
A neutral operator responsible for maintaining instantaneous balance of the grid system. The ISO performs its function by controlling the dispatch of flexible plants to ensure that loads match resources available to the system.

In biology, any biological entity or processes, or community whose characteristics show the presence of specific environmental conditions. 2. In chemistry, a substance that shows a visible change, usually of color, at a desired point in a chemical reaction. 3. A device that indicates the result of a measurement; e.g. a pressure gauge or a moveable scale.

Indigenous Energy Resources:
Power and heat derived from sources native to California. These include geothermal, hydro, biomass, solar and wind energy. The term usually is understood to include cogeneration facilities.

Indirect Discharge:
Introduction of pollutants from a non-domestic source into a publicly owned waste-treatment system. Indirect dischargers can be commercial or industrial facilities whose wastes enter local sewers.

Indoor Air Pollution: Chemical, physical or biological contaminants in indoor air.

Indoor Air Quality (IAQ):
Acceptable IAQ is air in which there are no known contaminants at harmful concentrations as determined by cognizant authorities and with which a substantial majority (80 percent or more) of the people exposed do not express dissatisfaction.

Industrial Ecology:
An approach to the design of industrial products and processes that evaluates such activities through the dual perspectives of product competitiveness and environmental interactions.

Industrial Process Waste:
Residues produced during manufacturing operations.

Industrial Sludge:
Semi-liquid residue or slurry remaining from treatment of industrial water and wastewater.

Industrial Source Reduction:
Practices that reduce the amount of any hazardous substance, pollutant, or contaminant entering any waste stream or otherwise released into the environment. Also reduces the threat to public health and the environment associated with such releases. Term includes equipment or technology modifications, substitution of raw materials, and improvements in housekeeping, maintenance, training or inventory control.

Industrial Waste: Unwanted materials from an industrial operation; may be liquid, sludge, solid, or hazardous waste.

Inert Waste:
Waste that undergoes no significant physical, chemical or biological transformation. Inert waste does not dissolve burn or otherwise physically or chemically react. It is not biodegradable and does not adversely affect other matter with which it comes into contact in a way likely to give rise to environmental pollution or harm to health.

Inert Ingredient:
Pesticide components such as solvents, carriers, dispersants, and surfactants that are not active against target pests. Not all inert ingredients are innocuous.

Inertial Separator:
A device that uses centrifugal force to separate waste particles.

Infectious Agent:
Any organism, such as a pathogenic virus, parasite, or bacterium, that is capable of invading body tissues, multiplying, and causing disease.

Infectious Waste:
Hazardous waste capable of causing infections in humans, including: contaminated animal waste; human blood and blood products; isolation waste, pathological waste; and discarded sharps (needles, scalpels or broken medical instruments).

1. The penetration of water through the ground surface into sub-surface soil or the penetration of water from the soil into sewer or other pipes through defective joints, connections, or manhole walls. 2. The technique of applying large volumes of waste water to land to penetrate the surface and percolate through the underlying soil.

The uncontrolled inward leakage of air through cracks and gaps in the building envelope, especially around windows, doors and duct systems.

Infiltration Barrier:
A material placed on the outside or the inside of exterior wall framing to restrict inward air leakage, while permitting the outward escape of water vapor from the wall cavity.

Infiltration Gallery: A sub-surface groundwater collection system, typically shallow in depth, constructed with open-jointed or perforated pipes that discharge collected water into a watertight chamber from which the water is pumped to treatment facilities and into the distribution system. Usually located close to streams or ponds.

Infiltration Rate: The quantity of water that can enter the soil in a specified time interval.

Inflow: Entry of extraneous rain water into a sewer system from sources other than infiltration, such as basement drains, manholes, storm drains, and street washing.

Influent: Water, wastewater, or other liquid flowing into a reservoir, basin, or treatment plant.

Generally refers to the recharging and refueling network necessary to successful development, production, commercialization and operation of alternative fuel vehicles, including fuel supply, public and private recharging and refueling facilities, standard specifications for refueling outlets, customer service, education and training, and building code regulations.

Inhalable Particles: All dust capable of entering the human respiratory tract.

Injection (Petroleum):
Forcing gas or water into an oil well to increase pressure and cause more oil to come to the surface.

Injection Well: A well into which fluids are injected for purposes such as waste disposal, improving the recovery of crude oil, or solution mining.

Injection Zone:
A geological formation receiving fluids through a well.

Innovative Technologies: New or inventive methods to treat effectively hazardous waste and reduce risks to human health and the environment.

Innovative Treatment Technologies:
Technologies whose routine use is inhibited by lack of data on performance and cost.

1. Bacteria or fungi injected into compost to start biological action. 2. A medium containing organisms, usually bacteria or a virus, that is introduced into cultures or living organisms.

Inorganic Chemicals:
Chemical substances of mineral origin, not of basically carbon structure.

Inorganic Waste:
Waste composed of material other than plant or animal matter, such as sand, dust, glass, and many synthetics.

Insecticide: A pesticide compound specifically used to kill or prevent the growth of insects.

Insolation: The total amount of solar radiation (direct, diffuse, and reflected) striking a surface exposed to the sky.

Institutional Waste:
Waste generated at institutions such as schools, libraries, hospitals, prisons, etc.

Instream Use: Water use taking place within a stream channel; e.g., hydro-electric power generation, navigation, water quality improvement, fish propagation, recreation.

Insulation, Thermal:
A material having a relatively high resistance of heat flow and used principally to retard heat flow.

Integrated Exposure Assessment: Cumulative summation (over time) of the magnitude of exposure to a toxic chemical in all media.

Integrated Pest Management (IPM):
A mixture of chemical and other, non-pesticide, methods to control pests.

Integrated Pollution Prevention and Control (IPPC):
IPPC Directive is about minimizing pollution from various point sources throughout the European Union. Based on the concept of Best Available Techniques (or BAT),

Integrated Resource Planning (IRP):
A public planning process and framework within which the costs and benefits of both demand- and supply-side resources are evaluated to develop the least-total-cost mix of utility resource options. In many states, IRP includes a means for considering environmental damages caused by electricity supply/transmission and identifying cost-effective energy efficiency and renewable energy alternatives. IRP has become a formal process prescribed by law in some states and under some provisions of the Clean Air Act amendments of 1992.

Integrated Resource Planning Principles:
The underlying principles of IRP can be distinguished from the formal process of developing an approved utility resource plan for utility investments in supply- and demand-side resources. A primary principle is to provide a framework for comparing a variety of supply- and demand-side and transmission resource costs and attributes outside of the basic provision (or reduction) of electric capacity and energy. These resources may be owned or constructed by any entity and may be acquired through contracts as well as through direct investments. Another principle is the incorporation of risk and uncertainty into the planning analysis. The public participation aspects of IRP allow public and regulatory involvement in the planning rather than the siting stage of project development.

Integrated Services Digital Network (ISDN):
A 128 Kbps (kilobytes per second) digital telephone service available in many parts of the country though not universally available that may be able to substitute for fiber optic cable in every respect except possibly television transmission.

Integrated Solid Waste Management:
Coordinated use of a set of waste management methods, each of which can play a role in an overall MSVVM plan.

Integrated Waste Management:
Using a variety of practices to handle municipal solid waste; can include source reduction, recycling, incineration, and landfilling.

Interceptor Sewers:
Large sewer lines that, in a combined system, control the flow of sewage to the treatment plant. In a storm, they allow some of the sewage to flow directly into a receiving stream, thus keeping it from overflowing onto the streets. Also used in separate systems to collect the flows from main and trunk sewers and carry them to treatment points.

Interchange (Electric Utility):
The agreement among interconnected utilities under which they buy, sell and exchange power among themselves. This can, for example, provide for economy energy and emergency power supplies.

Interconnection (Electric Utility): The linkage of transmission lines between two utilities, enabling power to be moved in either direction. Interconnections allow the utilities to help contain costs while enhancing system reliability.

Interested Party: Any person whom the commission finds and acknowledges as having a real and direct interest in any proceeding or action carried on, under, or as a result of the operation of, this division.

Interface: The common boundary between two substances such as a water and a solid, water and a gas, or two liquids such as water and oil.

Interfacial Tension: The strength of the film separating two immiscible fluids (e.g. oil and water) measured in dynes per, or millidynes per centimetre.

Internal Combustion Engine: An engine in which fuel is burned inside the engine. A car's gasoline engine or rotary engine is an example of a internal combustion engine. It differs from engines having an external furnace, such as a steam engine.

Internal Dose:
In exposure assessment, the amount of a substance penetrating the absorption barriers (e.g. skin, lung tissue, gastrointestinal tract) of an organism through either physical or biological processes.

International Standards Organization (ISO):
A non-governmental organization chartered to develop voluntary technical standards that aim to make the development, manufacture and supply of goods and services safer, cleaner and more efficient.

Interruptible Service (Electric Utility):
Electricity supplied under agreements that allow the supplier to curtail or stop service at times.

Interstate Carrier Water Supply:
A source of water for drinking and sanitary use on planes, buses, trains, and ships operating in more than one state. These sources are federally regulated.

Interstitial Monitoring: The continuous surveillance of the space between the walls of an underground storage tank.

Inversion: A layer of warm air that prevents the rise of cooling air and traps pollutants beneath it; can cause an air pollution episode.

Intertie: A transmission line that links two or more regional electric power systems.

Ion: An electrically charged atom or group of atoms.

Ion Exchange Treatment: A common water-softening method often found on a large scale at water purification plants that remove some organics and radium by adding calcium oxide or calcium hydroxide to increase the pH to a level where the metals will precipitate out.

Ionization Chamber: A device that measures the intensity of ionizing radiation.

Ionizing Radiation: Radiation that can strip electrons from atoms; e.g. alpha, beta, and gamma radiation.

Irradiated Food: Food subject to brief radioactivity, usually gamma rays, to kill insects, bacteria, and mould, and to permit storage without refrigeration.

Irradiation: Exposure to radiation of wavelengths shorter than those of visible light (gamma, x-ray, or ultra- violet), for medical purposes, to sterilize milk or other foodstuffs, or to induce polymerization of monomers or vulcanization of rubber.

Irreversible Effect: Effect characterized by the inability of the body to partially or fully repair injury caused by a toxic agent.

Irrigation: Applying water or wastewater to land areas to supply the water and nutrient needs of plants.

Irrigation Efficiency:
The amount of water stored in the crop root zone compared to the amount of irrigation water applied.

Irrigation Return Flow: Surface and subsurface water which leaves the field following application of irrigation water.

Irritant: A substance that can cause irritation of the skin, eyes, or respiratory system. Effects may be acute from a single high level exposure, or chronic from repeated low-level exposures to such compounds as chlorine, nitrogen dioxide, and nitric acid.

ISO: International Standards Organization.

ISO 9001 Quality Management Systems: The ISO 9001 standard assesses the capacity of an organization to meet the client's requirements with regards to the quality of a product or service.

ISO 14001 Environmental Management Systems:
The ISO 14001 standard evaluates the ability of an organization to control the impact on the environment of its activities and to comply with regulations.

ISO 14031: This standard evaluates an organization's compliant use of management indicators, comparing the past and present environmental performance of the company's business on the basis of the "plan, do, check, act" process.

More than one sample point exhibiting the same isolate concentration.

Isopleth: The line or area represented by an isoconcentration.

A variation of an element that has the same atomic number of protons but a different weight because of the number of neutrons. Various isotopes of the same element may have different radioactive behaviours, some are highly unstable..

The condition in which the hydraulic or other properties of an aquifer are the same in all directions.

Itinerant Waste Buyer: A person who moves around the streets buying (or bartering for) reusable and recyclable materials.