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Operable Unit: Term for each of a number of separate activities undertaken as part of a Superfund site cleanup.

Opacity: The amount of light obscured by particulate pollution in the air; clear window glass has zero opacity, a brick wall is 100 percent opaque. Opacity is an indicator of changes in performance of particulate control systems.

On-Screen Coordinator: The predesignated EPA, Coast Guard, or Department of Defense official who coordinates and directs Superfund removal actions or Clean Water Act oil- or hazardous-spill response actions.

Occupational Safety and Health Administration (OSHA): Created by Congress to assure safe and healthful working conditions for workers by setting and enforcing standards and by providing training, outreach, education and assistance.

Nutrient: Any substance assimilated by living things that promotes growth. The term is often applied to nitrogen and phosphorus in wastewater, where excessive amounts create algae growth and other problems, but is also applied to other essential and trace elements.

Nuclear Regulatory Commission (NRC): The NRC was created as an independent agency by Congress in 1974 to ensure the safe use of radioactive materials for beneficial civilian purposes while protecting people and the environment. The NRC regulates commercial nuclear power plants like Palo Verde Nuclear Generating Station west of Phoenix.

Noxious Gases: Poisonous gases that can harm people and the environment. Some gases have a strong smell, for example sulfur dioxide and methane, while others, such as carbon monoxide, do not have any smell at all.

Notice of Violation (NOV): An informal enforcement action taken by ADEQ which documents the factual nature of an environmental violation, the legal authority regarding compliance, a description of what constitutes compliance and how it is to be documented and a time frame in which ADEQ expects compliance to be achieved. NOVs are issued for violations considered to pose higher environmental risk than NOC violations

Notice of Opportunity to Correct (NOC): An informal enforcement action taken by ADEQ which documents the factual nature of an environmental violation, the legal authority regarding compliance, a description of what constitutes compliance and how it is to be documented and a time frame in which ADEQ expects compliance to be achieved. NOCs are issued for violations considered to pose less environmental risk than NOV violations.

North American Development Bank (NADB): Created with the Border Environment Cooperation Commission (BECC) as an interdependent institution, NADB concentrates on project financing and oversight for project implementation to preserve and enhance environmental conditions for people living along the U.S.-Mexico border.

Non-Point Sources: Diffuse pollution sources (i.e. without a single point of origin or not introduced into a receiving stream from a specific outlet). The pollutants are generally carried off the land by storm water. Common non-point sources are agriculture, forestry, urban, mining, construction, dams, channels, land disposal, saltwater intrusion, and city streets.

Non-Attainment Area: Area that does not meet one or more of the National Ambient Air Quality Standards for the criteria pollutants designated in the Clean Air Act.

No Burn Day: Admonition to not burn wood issued by Maricopa County Air Quality Department when forecasted soot, dust or ozone conditions have led to issuance of a high pollution advisory or health watch by ADEQ.

Nitrogen oxides:Any inorganic compound containing both nitrogen and oxygen. These compounds act as precursors to other pollutants such as nitrate and ozone.

Nitrate: A compound containing nitrogen and oxygen that exists in the atmosphere or as a dissolved gas in water and has harmful effects on humans and animals. Nitrates in water can cause severe illness in infants and domestic animals. A plant nutrient and inorganic fertilizer, nitrate is found in septic systems, animal feed lots, agricultural fertilizers, manure, industrial waste waters, and sanitary landfills.

New Source Review: A Clean Air Act requirement that state implementation plans must include a permit review that applies to the construction and operation of new and modified stationary sources in nonattainment areas to ensure attainment of national ambient air quality standards.

New Source Performance Standards: Uniform national EPA air emission and water effluent standards which limit the amount of pollution allowed from new sources or from modified existing sources.

Navigable Waters: Traditionally, waters sufficiently deep and wide for navigation by all, or specified vessels. Such waters in the United States come under federal jurisdiction and are protected by certain provisions of the Clean Water Act.

National Response Team: Representatives of 13 federal agencies that, as a team, coordinate federal responses to nationally significant incidents of pollution — an oil spill, a major chemical release, or a superfund response action — and provide advice and technical assistance to the responding agency(ies) before and during a response action.

National Response Center (NRC): The federal government’s national communications center, which is staffed by U.S. Coast Guard officers and marine science technicians. The NRC is the sole federal point of contact for reporting all hazardous substances releases and oil spills.

National Priorities List (NPL): EPA’s list of the most serious hazardous waste sites identified for possible long-term remedial response under the federal superfund (CERCLA).

National Pollution Discharge Elimination System (NPDES): Provision of the Clean Water Act which prohibits discharge of pollutants into waters of the United States unless a special permit is issued by EPA, a state, or, where delegated, a tribal government on an Indian reservation.

National Institute for Occupational Safety and Health (NIOSH): The federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the Centers for Disease Control and Prevention.

National Environmental Policy Act of 1969: An act that established a U.S. national policy promoting the enhancement of the environment. NEPA’s most significant accomplishment was setting up procedural requirements for all federal government agencies to prepare environmental assessments and environmental impact statements.

National Emissions Standards for Hazardous Air Pollutants (NESHAP): Emissions standards set by EPA for an air pollutant not covered by NAAQS that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness. Primary standards are designed to protect human health, secondary standards to protect public welfare like building facades, visibility, crops, and domestic animals.

National Ambient Air Quality Standards (NAAQS): Federal standards for the minimum ambient air quality needed to protect public health and welfare.

Multiple Use: Use of land for more than one purpose like grazing of livestock, watershed and wildlife protection, recreation, and timber production. Also applies to use of bodies of water for recreational purposes, fishing, and water supply.

Monsoon (North American): A seasonal change in prevailing winds accompanied by corresponding increase in precipitation. It describes the seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. It is formally defined as occurring from June 15 to September 30.

Monitoring Wells: Wells installed for the purpose of collecting samples such as groundwater and soil gas. Analytical results from samples are used to characterize the extent of contamination, the direction of groundwater flow, and the types and quantities of contaminants present in the groundwater.

Monitoring Assistance Program (MAP): ADEQ program designed to lessen the monitoring and financial burdens on small public water systems in Arizona to ensure that all water served meets state and federal safe drinking water standards.

Monitored Natural Attenuation (MNA): Describes a range of physical and biological processes which, unaided by human intervention, reduce the concentration, toxicity, or mobility of chemical or radioactive contaminants. These processes take place whether or not other active cleanup measures are in place.

Mixing Zone: an area or volume of a surface water that is contiguous to a point source discharge where dilution of the discharge takes place.

Mixing Height: The height to which the lower atmosphere will undergo mechanical or turbulent mixing, producing a nearly uniform air mass.

Million Gallons per Day (MGD): A measure of water flow often used for indicating the treatment capacity of sewage treatment plants or production capacity of drinking water treatment plants. One MGD is equivalent to about 700 gallons per minute or 1.5 cubic feet per second.

Milligrams per Liter (mg/L): A unit of measurement that expresses a concentration that is the mass (weight) of one material dissolved into a volume of another material. A milligram is a metric unit of mass equal to 0.0000022 pounds or 1000 micrograms. A liter is a metric unit of volume approximately equivalent to 1 quart. Also, 1 mg/L is equivalent to 1 part per million (ppm).

Migration: The movement of a contaminant in the environment through soil, groundwater, surface water, air, etc.

Micrograms per Liter (μg/L) : A unit of measurement that expresses a concentration that is the mass (weight) of one material dissolved into a volume of another material. A microgram (μg) is a metric unit of mass which is equivalent to 0.0000000022 pounds. A liter is a metric unit of volume which is approximately equivalent to a quart. Also, 1 μg/L is equivalent to 1 part per billion (ppb).

Methane: A colorless, non-poisonous, flammable gas created by microorganisms as they digest (anaerobic decomposition) organic compounds found in landfill wastes. Methane is found in nature as a gas and is the major component of the gas that provides energy for our homes.

Medical Waste Incinerator (MWI): Incineration equipment that burns wastes produced by hospitals, veterinary facilities, and medical research facilities. These wastes include both infectious medical wastes as well as non-infectious, general housekeeping wastes.

Maximum Contaminant Level (MCL): A federally designated, enforceable drinking water standard set to ensure that water is safe for drinking and other uses. The MCL varies for each contaminant being analyzed.

Maricopa Association of Governments (MAG): Regional air quality planning agency and metropolitan planning organization for transportation for all jurisdictions in Maricopa County, including the Phoenix urbanized area and the contiguous urbanized area in Pinal County, including the Town of Florence and City of Maricopa.

Manifest (Hazardous Waste): The shipping document, originated and signed by a waste generator or his or her representative, that is required by state or federal environmental regulators.

Leaking Underground Storage Tank (LUST): Petroleum releases from regulated underground storage tanks.

Lead: A heavy metal that is hazardous to health if breathed or swallowed. Its use in gasoline, paints and plumbing compounds has been sharply restricted or eliminated by federal laws and regulations.

Leachate: Liquid that forms when water passes down through solid waste, carrying suspended particles and chemicals it picks up and dissolves along the way into the ground and groundwater below. For example, rain falling on a landfill and passing through the waste would appear as leachate below the waste.

Large Quantity Generators (LQG): Facilities that generate more than 2,200 pounds of hazardous waste per calendar month, or more than 2.2 pounds of acutely hazardous waste per calendar month.

Landfill Gas: Refers to the carbon dioxide, methane, and other compounds produced during the decomposition of organic waste.

Landfill: A location on land where wastes are placed for permanent disposal.

Lamp: Also referred to as “universal waste lamp,” a lamp is defined as the bulb or tube portion of an electric lighting device.

Ladle Metallurgical Furnace: A cylindrical furnace, which is lined with a material capable of enduring high temperatures, that is used for adjusting the chemical and mechanical properties of the molten steel produced in the electric arc shaft furnace.

LaPaz Agreement: 1983 agreement between the U.S. and Mexico to cooperate for protection and improvement of the environment in the border area. The agreement defines the border as 62 miles (100 kilometers) north and south of the international border.

Inversion: A departure from the usual decrease of temperature with altitude. Also, the layer through which this departure occurs (the “inversion layer”), or the lowest altitude at which the departure is found (the “base of the inversion”). Inversions, which are common in winter in the Phoenix area, can trap pollutants near the surface resulting in what is commonly known as the “brown cloud.”

International Outfall Interceptor (IOI): A 30-inch pipe that serves Nogales, Arizona, and Nogales, Sonora, with wastewater collection. The IOI conveys wastewater from the border with Mexico over a distance of 10 miles to the Nogales International Wastewater Treatment Plant in Rio Rico, Arizona. The IOI runs both under and adjacent to the Nogales Wash.

International Boundary and Water Commission: Mission is to provide binational solutions to issues that arise during the application of United States – Mexico treaties regarding boundary demarcation, national ownership of waters, sanitation, water quality, and flood control in the border region. Also includes Mexican section. The U.S. section, located in El Paso, Texas, is administered by the Department of State; the Mexican section, located in Ciudad Juarez, Chihuahua, is known as Comisión Internacional de Límites y Aguas (CILA) and is administered by the Secretariat of Foreign Relations. The U.S. IBWC operates the Nogales International Wastewater Treatment Plant located in Rio Rico.

Intermittent Water: A stream or reach that flows continuously only at certain times of the year, as when it receives water from rainfall or snow melt.

Interim Remedial Actions (IRA): Minimum remedial actions taken to address the loss or reduction of available water from a well until a remedy is selected.

Integrated Pest Management: The coordinated use of pest and environmental information with available pest control methods to prevent unacceptable levels of pest damage by the most economical means and with the least possible hazard to people, property, and the environment

Institutional Controls (ICs):  Actions, such as legal controls that help minimize the potential for human exposure to contamination by ensuring appropriate land or resource use. ICs are meant to supplement engineering controls, and they are rarely the sole remedy at a site. ICs are commonly used when residual contamination remains onsite at a level that does not allow for unrestricted use and unlimited exposure after cleanup.

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

Inorganic Compounds: Compounds that are considered to be of mineral as opposed to biological.

Injection Well: A well in which fluids are injected rather than produced as when treated water is put back into the aquifer after contaminants have been removed.

Infiltration: The flow of a fluid into a substance through pores or small openings.

Impervious Surface: A surface which does not allow water or other liquids to pass through. Impervious surfaces greatly increase the volume and velocity of runoff and the amount of pollution and sediment that enters streams and lakes.

Information Repository: A collection of documents about a specific project. Information on certain WQARF and Superfund sites may be available at ADEQ offices and libraries throughout the state.

Indian Country: As defined in U. S. Code Title 18 §1151 , Indian Country includes all land within the limits of any Indian reservation under the jurisdiction of the U. S. government, all dependent Indian communities within the borders of the U. S., and all Indian allotments to which the Indian titles have not been extinguished. The Arizona Department of Environmental Quality does not have discharge permitting authority in Indian Country, even on private fee lands. Operators in Indian Country must pursue permitting through U.S. EPA Region 9 or federally recognized tribes granted “treatment as state” status or primacy by U.S. EPA over specific environmental programs.

Hydrology: TThe study of the movement, distribution, and quality of water throughout the earth.

Hydrogeology: TThe part of hydrology that deals with the distribution and movement of groundwater in the soil and rocks of the earth’s crust, most commonly in aquifers.

Hydraulics: TThe study of the behavior of fluids, static (not moving) and dynamic (moving).

Human Health Risk Assessment: An evaluation of available data on existing or potential risks to human health posed by a contaminated site.

Household Hazardous Waste (HHW): Hazardous products used and disposed of by residential consumers. Those products include paints, stains, varnishes, solvents, pesticides, and other materials or products containing volatile chemicals that can catch fire, react or explode, or that are corrosive or toxic.

Holding Pond: A pond or reservoir, usually made of earth, built to store polluted runoff.

High Pollution Advistory (HPA): Issued when air pollution levels are reaching unhealthy levels for everyone, not just people with respiratory problems. HPAs encourage people to limit outdoor activity and reduce driving and other activities that cause air pollution.

Heavy Metals: Refers to a group of toxic metals including arsenic, chromium, copper, lead, mercury, silver, and zinc. Heavy metals often are present at industrial sites where operations have included battery recycling and metal plating.

Heat Island Effect: A “dome” of elevated temperatures over an urban area caused by structural and pavement heat fluxes, and pollutant emissions.

Health Based Guidance Level (HBGL): Represents  human ingestion (drinking) levels that are unlikely to result in adverse health effects during long-term exposure. The HBGLs are recommended maximum levels and not legally enforceable. However, the HBGLs can be referred to when there are no regulatory levels specified by law or regulation

Hazardous Waste Operator Certification: The training process to meet guidelines produced and maintained by the Occupations Safety and Health Administration that regulates hazardous waste operations and emergency services.

Hazardous Substance: Any material that, because of its quantity, concentration, and physical or chemical characteristics, poses a significant present or potential hazard to human health and safety or to the environment.

Hazardous Air Pollutants (HAPs): Air pollutants which are not covered by ambient air quality standards but which, as defined in the Clean Air Act, may present a threat of adverse human health effects or adverse environmental effects. Such pollutants include asbestos, beryllium, mercury, benzene, coke oven emissions, radionuclides, and vinyl chloride.

Groundwater Model: Refers to computer models of groundwater flow systems that are used by hydrogeologists to simulate and predict aquifer conditions. Models can be used to help summarize, interpret, and present available data; to evaluate such things as monitoring networks or alternate remedial measures; to compare and assess different hypothetical groundwater flow conditions; and to help with water management problems such as predicting changes to the water table due to human activities.

Groundwater Basin: A groundwater reservoir defined by an overlaying land surface and the underlying aquifers that contain the stored groundwater. In some cases, the boundaries of successively deeper aquifers may differ and make it difficult to define the limits of the basin.

Groundwater: Water located beneath the ground surface in soil pore spaces and in the fractures of geologic formations. A formation of rock or soil is called an aquifer when it can yield a usable quantity of water.

Greenwashing: A form of corporate misrepresentation where a company will present a green public image and publicize green initiatives that are false or misleading.