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Air Model. A mathematical simulation of how air pollutants disperse in the ambient atmosphere.

Air Pollutant. Generally an airborne substance that could, in high enough concentrations, harm living things or cause damage to materials. From a regulatory perspective, an air pollutant is a substance for which emissions or atmospheric concentrations are regulated and for which maximum guideline levels have been established due to potential harmful effects on human health and welfare.

Air Quality. The cleanliness of the air as measured by the levels of pollutants relative to standards or guideline levels established to protect human health and welfare.

Affected Environment. A NEPA term that refers to a description of the environment of the area(s) to be affected or created by the alternatives under consideration. The description must include baseline information to create a basis for assessing or understanding the impacts that would result from implementation of the alternatives. It must contain enough detail to support the impact analyses and highlight environmentally sensitive resources (e.g., floodplains, wetlands, threatened and endangered species, and archeological resources).

Alternative: A NEPA term that refers to a way of achieving the same purpose and need for a project that is different from the recommended proposal; alternatives should be studied, developed, and described to address any proposal which involves unresolved conflicts concerning different uses of available resources. Analysis scenarios presented in a comparative form, to facilitate a sharp definition of the issues resulting in a basis for evaluation among options by the decision maker and the public.

Ambient. The environment as it exists at the point of measurement and against which changes or impacts are measured.

Aquatic Bird. Wading, swimming, and diving birds, such as waterfowl, shorebirds, seabirds, and rails.

Aquifer. A body of rock that is sufficiently permeable to conduct groundwater and yield economically significant quantities of water to wells, springs, sands, and soils.

Archaeological Resource. Any material remains of past human life or activities of archaeological interest. These include, but are not limited to: pottery, basketry, bottles, weapons, projectiles, tools, structures or portions of structures, pit houses, rock paintings, rock carvings, intaglios, graves, human skeletal materials, or any portion or piece of any of the foregoing items. Non-fossilized and fossilized paleontological specimens, or any portion or piece thereof, shall not be considered archaeological resources unless found in an archaeological context. No item shall be treated as an archaeological resource unless such item is at least 100 years of age.

Archaeological Site. A geographic locale that contains the material remains of prehistoric or historic human activity.

Archaeology. The reconstruction of past cultures through their material remains and the study of how cultures change over time.

Assumptions (for analysis). The basis for framing the analysis. Assumptions often are identified at the beginning of the environmental consequences section of an EA or EIS and, as needed, at the beginning of the program-specific environmental consequences analysis.

Attainment Area. An area that the U.S. Environmental Protection Agency has designated as being in compliance with one or more of the National Ambient Air Quality Standards (NAAQS) for sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, lead, and particulate matter. An area may be in attainment for some pollutants but not for others. (See National Ambient Air Quality Standards (NAAQS), nonattainment area.)

Avian. Relating to birds.


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Baseline. The existing environmental conditions against which impacts of the proposed action and its alternatives can be compared. For a specific NEPA document, a further statement can be included about the date or conditions that are considered the baseline.

Best Available Control Technology (BACT). Available devices, systems, or techniques for achieving the maximum reduction of air pollutant emissions while considering energy, environmental, and economic impacts. BACT is determined on a case-by-case basis for new sources or major modifications to existing sources in areas that are in attainment of NAAQS. BACT does not permit emissions in excess of those allowed under any Clean Air Act provisions. [See Lowest Achievable Emissions Rate (LAER), Maximum Achievable Control Technology (MACT), Reasonably Achievable Control Technology (RACT), and National Ambient Air Quality Standards (NAAQS).]

Best Available Retrofit Technology (BART). An emission limitation to reduce regional haze, based on the degree of reduction achievable through the application of the best system of continuous emission reduction for each pollutant which is emitted by an existing stationary facility. The emission limitation must be established, on a case-by-case basis, taking into consideration the technology available, the costs of compliance, the energy and non-air quality environmental impacts of compliance, any pollution control equipment in use or in existence at the source, the remaining useful life of the source, and the degree of improvement in visibility which may reasonably be anticipated to result from the use of such technology. (40 CFR 51.301).


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Candidate Species. An ESA term that refers to a plant or animal species for which the USFWS or NOAA Fisheries has on file sufficient information on biological vulnerability and threats to support a proposal to list as endangered or threatened.

Class I Area. A specifically designated area where the degradation of air quality is stringently restricted (e.g., many national parks, wilderness areas). (See Prevention of Significant Deterioration.)

Categorical Exclusion (CE). A NEPA term, referring to a category of actions that do not individually or cumulatively have a significant effect on the human environment and have been found to have no such effect in procedures adopted by a Federal agency pursuant to NEPA.

Climate. The average or prevailing weather conditions of a place over a lengthy period of years (Bureau of Land Management Technical Reference 4400-7).

Colorado River Compact of 1922. Provides for the equitable division and apportionment of the use of the waters of the Colorado River System between the Upper Basin states (Colorado, New Mexico, Utah, and Wyoming) and the Lower Basin states (Arizona, California, and Nevada).

Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). A Federal law (also known as Superfund), enacted in 1980 and reauthorized in 1986, that provides the legal authority for emergency response and cleanup of hazardous substances released into the environment and for the cleanup of inactive waste sites.

Cooperating Agency. A NEPA term, referring to any Federal agency, other than a lead agency, that has jurisdiction by law or special expertise with respect to any environmental impact involved in a proposed project or project alternative. A State or local agency of similar qualifications or, when the effects are on lands of tribal interest, a Native American tribe may, by agreement with the lead agencies, also become a cooperating agency.

Council on Environmental Quality (CEQ). Established under Title II of NEPA to develop Federal agency-wide policy and regulations for implementing the procedural provisions of NEPA, resolve interagency disagreements concerning proposed major Federal actions, and ensure that Federal agency programs and procedures are in compliance with NEPA.

Conservation Agreement. An ESA term referring to a voluntary agreement between FWS or NOAA Fisheries and other federal or non-federal landowners to identify specific conservation measures that the participants of the agreement will undertake to conserve species covered by the agreement, none of which are listed under the Endangered Species Act, with the intention of preventing any need to list the species.

Consumptive Use. The portion of water withdrawn from a surface or groundwater source that is consumed for a particular use (i.e. irrigation, domestic needs, and industry), and does not return to its original source or another body of water.

Critical Habitat (threatened and endangered species). As used by the ESA, the specific areas within the geographical area occupied by the species that contain those physical or biological features essential to the considerations or protection, and specific areas outside the geographical area occupied by the species, that are essential for the conservation of the species.

Criteria Pollutant. An air pollutant that is regulated by NAAQS. The Environmental Protection Agency must describe the characteristics and potential health and welfare effects that form the basis for setting, or revising, the standard for each regulated pollutant. Criteria pollutants include sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, lead, and two size classes of particulate matter, less than 10 micrometers (0.0004 inch) in diameter, and less than 2.5 micrometers (0.0001 inch) in diameter. Pollutants may be added to, or removed from, the list of criteria pollutants as more information becomes available. (See National Ambient Air Quality Standards.) Note: Sometimes pollutants regulated by state laws also are called criteria pollutants.

Cultural Property. A definite location of past human activity, occupation, or use identifiable through field inventory (survey), historical documentation, or oral evidence (BLM Manual 8100).

Cultural Resources. A general term meaning any cultural property and any traditional lifeway value (BLM Manual 8100). It includes prehistoric, historic, ethnographic, tribal heritage, ethnohistoric, engineering, architectural, and technological resources.

Cultural Resources Investigations

Class I (Files Search) Inventory. A file search completed to identify all previously conducted cultural resources investigations and previously recorded cultural resources within a defined distance (typically 1 mile) on either side of proposed rights-of-way, roads, and other project facilities.

Class II Inventory. A reconnaissance-level Inventory typically combined with a Class I Inventory. Class II is usually used as a methodology in large scale projects for locating areas with good or better cultural resources potential to determine whether previously recorded cultural resources exist within the proposed project area, and to determine whether portions of the project area have been adequately surveyed in the recent past.

Class III (Pedestrian) Inventory. A Class III intensive field inventory to locate and record cultural resources and places of traditional, cultural, and religious importance to Native Americans.

Cumulative Effect/Cumulative Impact. As used by NEPA, the impact or impacts that result from identified actions when they are added to other past, present, and reasonably foreseeable future actions regardless of who undertakes such other actions. Cumulative effects can result from individually minor but collectively significant actions taking place over a period of time.


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Designated Wilderness. See Wilderness.

Drawdown. The lowering of the water level in a well, spring, or water body as a result of water withdrawal in another area; the reduction in head at a point caused by the withdrawal of water from an aquifer.

Drawdown Contour. A boundary derived from water modeling that depicts a certain reduction in the water level compared to its previous level.


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Earnings. Wages and salaries, other labor income, and proprietor’s income (including inventory valuation and capital consumption adjustments).

Ecological Resources. Animals, plants, and the habitats in which they live.

Ecological System. All the organisms in a particular region and the environment in which they live. The elements interact with each other in some way, and so depend on each other either directly or indirectly.

Ecology. The science of the interrelationships between organisms and their environment.

Effluent. A waste stream flowing into the atmosphere, surface water, groundwater, or soil. Most frequently the term applies to wastes discharged to surface waters.

Endangered Species. Any species defined through the Endangered Species Act of 1973, as amended, as being in danger of extinction throughout all or a significant portion of its range; designations of endangered species are published in the Federal Register.

Endangered Species Act (ESA) of 1973, as amended. Federal legislation intended to provide a means to conserve the ecosystems upon which endangered and threatened species depend, and which provides programs for the conservation of those species, thus preventing extinction of plants and animals.

Endemic Species. Species native to, and restricted to, a particular geographical region, community type, or specific habitat; generally used for species with comparatively restricted distribution.

Environmental Assessment (EA). A NEPA term, which refers to a concise public document that a federal agency prepares under the National Environmental Policy Act to provide sufficient evidence and analysis to determine whether a proposed action requires preparation of an Environmental Impact Statement (EIS) or whether a Finding of No Significant Impact can be issued. An EA must include brief discussions on the need for the proposal, the alternatives, the environmental impacts of the proposed action and alternatives, and a list of agencies and persons consulted.

Environmental Consequences. Environmental effects of project alternatives, including the proposed action, which cannot be avoided; the relationship between short-term uses of the human environment, and any irreversible or irretrievable commitments of resources which would be involved if the proposal should be implemented.

Environmental Impact Statement (EIS). A NEPA term, referring to a formal document that is filed with the U.S. Environmental Protection Agency and that considers significant environmental impacts expected to result from implementation of a major federal action.

Environmental Justice. The fair treatment of people of all races, cultures, incomes, and educational levels with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies.


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Federal Register. The official daily publication for rules, proposed rules, and notices of federal agencies and organizations, as well as executive orders and other presidential documents.

Floodplain. A nearly level alluvial plain that borders a stream and is subject to inundation under flood‑stage conditions unless protected artificially. It is usually a constructional landform built of sediment deposited during overflow and lateral migration of the stream.

Fugitive Emissions. 1. Emissions that do not pass through a stack, vent, chimney, or similar opening where they could be captured by a control device. 2. Any air pollutant emitted to the atmosphere other than from a stack. Sources of fugitive emissions include pumps; valves; flanges; seals; area sources such as ponds, lagoons, landfills, piles of stored material (e.g., coal); and road construction areas or other areas where earthwork is occurring.


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Geographic Information System (GIS). A computer system capable of storing, analyzing, and displaying data and describing places on the earth’s surface.

Greenhouse Gas. Gases which absorb outgoing terrestrial radiation, such as water vapor, methane, chlorofluorocarbons, and carbon dioxide.

Groundwater. Subsurface water that is in the zone of saturation. The top surface of the groundwater is the “water table.” Source of water for wells, seepage, springs.


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Habitat. An environment that meets a specific set of physical, biological, temporal, or spatial characteristics that satisfy the requirements of a plant or animal species or group of species for part or all of its life cycle.

Hazardous Air Pollutants (HAPs).Air pollutants not covered by the National Ambient Air Quality Standards but which may present a threat of adverse human health effects or adverse environmental effects. Those specifically listed in 40 CFR 61.01 are asbestos, benzene, beryllium, coke oven emissions, inorganic arsenic, mercury, radionuclides, and vinyl chloride. More broadly, HAPs are any of the 189 pollutants listed in or pursuant to section 112(b) of the Clean Air Act. Very generally, HAPs are any air pollutants that may realistically be expected to pose a threat to human health or welfare.

Hazardous Waste.A category of waste regulated under the Resource Conservation and Recovery Act (RCRA). To be considered hazardous, a waste must be a solid waste under RCRA and must exhibit at least one of four characteristics described in 40 CFR 261.20 through 40 CFR 261.24 (i.e., ignitability, corrosivity, reactivity, or toxicity) or be specifically listed by the Environmental Protection Agency in 40 CFR 261.31 through 40 CFR 261.33. Source, special nuclear, or by-product materials as defined by the Atomic Energy Act are not hazardous waste because they are not solid waste under RCRA.

Heavy Metals.Metallic and semimetallic elements that are generally highly toxic to plants and animals and that tend to accumulate in food chains. Heavy metals include lead, mercury, cadmium, chromium, and arsenic. . EPA regulation 40 CFR 258.4 refers to the following monitoring parameters as “heavy metals”: antimony, arsenic, barium, beryllium, cadmium, chromium, cobalt, copper, lead, nickel, selenium, silver, thallium, vanadium, and zinc. Note: The term “heavy metals” is deeply embedded in environmental usage and will doubtless continue to be used. However, some of the elements commonly called “heavy metals” are not heavy (e.g., beryllium) or are not true metals (e.g., arsenic). Therefore, “heavy metals” should be avoided whenever more precise wording can be substituted.

Historic Property. “…any prehistoric or historic district, site, building, structure, or object included in, or eligible for inclusion in, the National Register of Historic Places maintained by the Secretary of the Interior. The term includes, for purposes of these regulations, artifacts, records, and remains that are related to and located within such properties.

Hydrologically Connected. Areas where the groundwater is linked and flow is contiguous.


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Impact. An impact has both space and time components and can be described as the change in an environmental factor or characteristic over a specific period and within a defined area. The change results from a particular activity compared with the situation which would have occurred had the activity not been initiated. An impact may be beneficial or adverse.

Indian Trust Assets. Lands, natural resources, or other assets held in trust or restricted against alienation by the United States for Native American Tribes or individual Native Americans.

Indian Trust Resources. Those natural resources, either on or off Indian lands, retained by or reserved by or for Indian Tribes through treaties, statutes, judicial decisions, and Executive Orders, which are protected by a fiduciary obligation on the part of the United States.

Indigenous. Living naturally within a given area and part of the area’s flora or fauna prior to human settlement of the region.

Indirect Effect. A NEPA term that refers to effects caused by the Federal action that are later in time or farther removed in distance, but are still reasonably foreseeable. Indirect effects may include growth-inducing effects and other effects related to induced changes in the pattern of land use, population density or growth rate, and related effects on air and water and other natural systems, including ecosystems.

Intermittent Stream. A stream which carries water a considerable portion of the time, but which ceases to flow occasionally or seasonally because bed seepage and evapotranspiration exceed the available water supply.


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Jurisdictional Wetlands. Those wetlands protected by the Clean Water Act. They must have a minimumof one positive wetland indicator from each parameter (i.e., vegetation, soil, and hydrology). The U.S. Army Corps of Engineers requires a permit to fill or dredge jurisdictional wetlands.


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Key Observation Point. An observer position on a travel route used to determine visible area.


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Land Use Plan. A land use plan is a public document that sets aside different areas for different uses, and describes what activities are permitted or not, and any limitations or conditions associated with such use.

Lead Agency. The agency or agencies responsible for preparing the environmental impact statement.

Lowest Achievable Emission Rate (LAER). The emissions rate permitted for new sources or major modifications of existing sources in areas that are not in attainment of NAAQS. The LAER is defined on a case-by-case basis, according to the regulations found in 40 CFR 51.165.

Low-Income Population. Low-income populations, defined in terms of Bureau of the Census annual statistical poverty levels (Current Population Reports, Series P-60 on Income and Poverty), may consist of groups or individuals who live in geographic proximity to one another or who are geographically dispersed or transient (such as migrant workers or Native Americans), where either type of group experiences common conditions of environmental exposure or effect.


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Major Federal Action. A NEPA term referring to an action with effects that may be major and which is potentially subject to Federal control and responsibility (40 CFR 1508.18).

Maximum Achievable Control Technology (MACT). Technology for achieving the maximum control of air emissions from major sources of hazardous air pollutants, using particularly stringent control devices, as prescribed in 40 CFR 63.41 for new sources and in 40 CFR 63.51 for existing sources.

MinorityPopulation. Minority populations exist where either: (a) the minority population of the affected area exceeds 50 percent or (b) the minority population percentage of the affected area is meaningfully greater than in the general population or other appropriate unit of geographic analysis (such as a governing body’s jurisdiction, a neighborhood, census tract, or other similar unit). “Minority” refers to individuals who are members of the following population groups: American Indian or Alaskan Native; Asian or Pacific Islander; Black, not of Hispanic origin; or Hispanic. “Minority populations” include either a single minority group or the total of all minority persons in the affected area. They may consist of groups of individuals living in geographic proximity to one another or a geographically dispersed/transient set of individuals (such as migrant workers or Native Americans), where either type of group experiences common conditions of environmental exposure or effect.

Mitigate, Mitigation. 1) Avoiding or reducing possible adverse impacts to a resource by limiting the timing, location, or magnitude of an action and its implementation; 2) rectifying possible adverse impact by repairing, rehabilitating or restoring the affected environment or resource; 3) reducing or eliminating adverse impacts by preservation and maintenance operations during the life of an action.

Mitigation Measure. A measure or action taken to reduce the adverse impacts to the environment from implementation of a project or another action. Such measures may include avoidance, replacement, restoration, relocation, timing of operations, etc.

Monitoring. The periodic observation and orderly collection of data to evaluate: 1) Effects of management actions; and 2) effectiveness of actions in meeting management objectives (43 Code of Federal Regulations 4100.0.5). The orderly collection, analysis, and interpretation of resource data to evaluate progress toward meeting management objectives. (BLM Technical Reference 4400‑7).


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National Ambient Air Quality Standards (NAAQS). The allowable concentrations of air pollutants in the ambient (public outdoor) air. National ambient air quality standards are based on the air quality criteria and divided into primary standards (allowing an adequate margin of safety to protect the public health) and secondary standards (allowing an adequate margin of safety to protect the public welfare).

National Emissions Standards for Hazardous Air Pollutants (NESHAPs). Emissions standards set by the Environmental Protection Agency for air pollutants which are not covered by NAAQS and which may, at sufficiently high levels, cause increased fatalities, irreversible health effects, or incapacitating illness. These standards are found in 40 CFR Parts 61 and 63. NESHAPs are given for many specific categories of sources (e.g., equipment leaks, industrial process cooling towers, dry cleaning facilities, petroleum refineries).

National Environmental Policy Act of 1969 (NEPA). A Federal environmental law that established a U.S. national policy promoting the enhancement of the environment; also established the President’s Council on Environmental Quality (CEQ). NEPA’s most significant effect was to set up procedural requirements for all federal government agencies to prepare Environmental Assessments (EAs) and Environmental Impact Statements (EISs) containing statements of the environmental effects of proposed federal agency actions.

National Historic Preservation Act (NHPA). A federal law providing that property resources with significant national historic value be placed on the National Register of Historic Places. It does not require permits; rather, it mandates consultation with the proper agencies whenever it is determined that a proposed action might affect a historic property.

National Pollutant Discharge Elimination System (NPDES). A program authorized by the Clean Water Act which prohibits discharge of pollutants into waters of the United States unless a special permit is issued by the Environmental Protection Agency, a state, or, where delegated, a tribal government on an Indian reservation. The NPDES permit lists either permissible discharges, the level of cleanup technology required for wastewater, or both.

National Register of Historic Places. A register of districts, sites, buildings, structures, and objects, significant in American history, architecture, archaeology and culture, established by the National Historic Preservation Act and maintained by the Secretary of the Interior.

Native American. Of, or relating to, a tribe, people, or culture that is indigenous to the United States.

Native Species. With respect to a particular ecological system, a species that, other than as a result of an introduction, historically occurred or currently occurs in that ecological system.

Natural Recharge. Replenishment of groundwater storage from naturally-occurring surface water sources such as rain, snow-melt, or stream flows.

No Action Alternative. A NEPA term that refers to the alternative in which the proposed Federal action is not taken (40 CFR 1502.14(d)). For many Federal actions, the No Action Alternative represents a scenario in which current conditions and trends are projected into the future without another proposed action, such as updating a land management plan. In other cases, the No Action Alternative represents the future in which the Federal action does not take place and the project is not implemented. In the case of the Navajo Generating Station-Kayenta Mine Complex Project, under the No Action Alternative, the power plant would cease operation, the plant lease would not be renewed, and the Kayenta Mine permit revision application would not be approved.

Nonattainment Area. An area that the U.S. Environmental Protection Agency has designated as not meeting (i.e., not being in attainment of) one or more of the National Ambient Air Quality Standards (NAAQS) for sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, lead, and particulate matter. An area may be in attainment for some pollutants, but not for others. [See attainment area, National Ambient Air Quality Standards (NAAQS), and particulate matter.]

Notice of Intent (NOI). A notice published in the Federal Register that an environmental impact statement will be prepared and considered.


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Obligate Phreatophyte. Plants which typically require access to groundwater at shallow soil depths for the majority of the year.


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Paleontology. The study of fossils; what fossils tell us about the ecologies of the past, about evolution, and about our place, as humans, in the world. Informs us about interrelationship between the biological and geological components of ecosystems over time.

Particulate matter (PM), PM10, PM2.5. Any finely divided solid or liquid material, other than uncombined (i.e., pure) water. A subscript denotes the upper limit of the diameter of particles included. Thus, PM10 includes only those particles equal to or less than 10 micrometers (0.0004 inch) in diameter; PM2.5 includes only those particles equal to or less than 2.5 micrometers (0.0001 inch) in diameter. Note: The applicable regulations express the diameter as the aerodynamic diameter. This is not the true diameter, but is the diameter of a spherical particle of unit density (i.e., 1 gram/cubic centimeter) which behaves the same way as the particle under consideration. Thus, for example, a spherical particle 10 micrometers in diameter with greater than unit density would not be included as PM-10 because it would fall at the same rate as a particle with unit density and diameter greater than 10 micrometers.

Perennial Springs. A spring in which water is present during all seasons of the year.

Perennial Stream. A stream in which water is present during all seasons of the year.

Perennial Yield (sometimes also referred to as sustainable yield). The amount of usable water from a ground-water aquifer that can be economically withdrawn and consumed each year for an indefinite period of time. It cannot exceed the natural recharge to that aquifer and ultimately is limited to a maximum amount of discharge that can be utilized for beneficial use.

Permeability. The quality of the soil that enables water to move downward through the profile, measured as the number of inches per hour that water moves downward through the saturated soil.

Plume. The elongated volume of contaminated water or air originating at a pollutant source such as an outlet pipe or a smokestack. A plume eventually diffuses into a larger volume of less contaminated material as it is transported away from the source.

Prevention of Significant Deterioration (of air quality) (PSD). Regulations established to prevent significant deterioration of air quality in areas that already meet NAAQS. Specific details of PSD are found in 40 CFR 51.166. Among other provisions, cumulative increases in sulfur dioxide, nitrogen dioxide, and PM-10 levels after specified baseline dates must not exceed specified maximum allowable amounts. These allowable increases, also known as increments, are especially stringent in areas designated as Class I areas (e.g., national parks, wilderness areas) where the preservation of clean air is particularly important. All areas not designated as Class I are currently designated as Class II. Maximum increments in pollutant levels are also given in 40 CFR 51.166 for Class III areas, if any such areas should be so designated by EPA. Class III increments are less stringent than those for Class I or Class II areas.

Proponents. The non-Federal sponsors of a proposed project or undertaking that requires a Federal action. For the Navajo Generating Station-Kayenta Mine Complex Project, the proponents are Salt River Project Agricultural Improvement and Power District (SRP), which is the operating agent of the NGS, and Peabody Western Coal Company (PWCC), which is the owner/operator of the Kayenta Mine.

ProposedAction.A NEPA term referring to a plan that contains sufficient details about the intended actions to be taken, or that will result, to allow alternatives to be developed and its environmental impacts analyzed.

Public Scoping. A NEPA term referring to discussions with and disclosure to agencies and the public with regard to a project or undertaking wherein areas of concern or issues to be addressed in a NEPA document are determined. (See Scope and Scoping.)

Pumping Effects. Any impact to natural or man-made resources that can be directly attributed to groundwater pumping.


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Quaternary Active Fault. A geologic fault that has moved within the last 1.6 million years.


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Reasonably Achievable Control Technology (RACT). Technology for control of air pollutant emissions from existing sources in areas that are not in attainment of NAAQS. RACT may include devices, systems, process modifications, or other apparatus or techniques that are reasonably achievable taking into account: (1) the necessity of imposing such controls in order to attain and maintain an NAAQS; (2) the social, environmental, and economic impact of such controls; and (3) alternative means of providing for attainment and maintenance of such a standard.

Regional Haze. Visibility impairment that is caused by the emission of air pollutants from numerous sources located over a wide geographic area. Such sources include, but are not limited to, major and minor stationary sources, mobile sources, and area sources. (40 CFR 51.301)

Resource Conservation and Recovery Act (RCRA). A law that gives the U.S. Environmental Protection Agency the authority to control hazardous waste from “cradle to grave” (i.e., from the point of generation to the point of ultimate disposal), including its minimization, generation, transportation, treatment, storage, and disposal. RCRA also sets forth a framework for the management of non-hazardous solid wastes.

Reclamation. The process by which lands disturbed as a result of human activity are restored by grading, planting, seeding, etc., to stabilize the disturbed area and simulate original conditions.

Record of Decision. A NEPA term which refers to a document separate from but associated with an environmental impact statement (EIS) that publicly and officially discloses the responsible agency’s decision on the EIS alternative to be implemented.

Regional Air Quality. The measure in the outdoor atmosphere of one or more contaminants such as dust, fumes, gas, mist, odor, smoke, or vapor.

Reserve Power. The electrical energy required for Central Arizona Project pumping requirements, which is currently approximately two-thirds of the United States’ 24.3 percent interest in the power and energy generated at NGS.

Resource Management Plan. A Bureau of Land Management multiple-use planning document, prepared in accordance with Section 202 of the Federal Land Policy and Management Act, that:

  • Establishes resource conditions goals and objectives to be attained;
  • Allocates resources and identifies allowable uses;
  • Identifies land area for limited, restrictive, or exclusive uses; and
  • Provides guidance for implementation of the decisions made in the plan.

Runoff. Surface water, from rain, snow melt, or other sources, that flows off the surface of the land without sinking into the soil. The precipitation discharged into stream channels from an area.


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Sacred Landscapes. Natural places recognized by a cultural group as having spiritual or religious significance.

Sacred Site. Any specific, discrete, narrowly delineated location of federal land that is identified by an Indian tribe, or individual determined to be an appropriately authoritative representative of an Indian religion, as sacred by virtue of its established religious significance to, or ceremonial use by, an Indian religion; provided that the tribe or appropriately authoritative representative of an Indian religion has informed the agency of the existence of such a site (Executive Order 13007, Section 7 1[b][iii]).

Scope. The range of actions, alternatives, and impacts to be considered in an EA or EIS.

Scoping. An early and open process for determining the extent and variety of issues to be addressed and for identifying the significant issues related to a proposed action that should be evaluated in an EA or EIS.

Section 7 of the Endangered Species Act. Describes the responsibilities of Federal agencies in conserving threatened and endangered species.

Seep. Wet areas, normally not flowing, arising from an underground water source.

Significant. Use of this term in NEPA requires consideration of both context and intensity (40 CFR 1508.27): Context – significance of an action must be analyzed in its current and proposed short-and long-term effects on the whole of a given resource (e.g.-affected region) Intensity – Refers to the severity of the effect.

Slope. The inclination of the land surface from the horizontal. Percentage of slope is the vertical distance divided by horizontal distance, then multiplied by 100. For example, a slope of 20 percent is a drop of 20 feet in 100 feet of horizontal distance.

Socioeconomics. The social and economic conditions in the study area.

Special Status Species. Plant or animal species that are federally listed, proposed, or Bureau of Land Management or USFS sensitive species.

Spring. Flowing water originating from an underground source.

State Historic Preservation Officer (SHPO). The State officer charged with the identification and protection of prehistoric and historic resources in accordance with the National Historic Preservation Act.

Study Area. The physical extent of a resource as related to the area of the proposed project.

Surface Water. All bodies of water on the surface of the earth and open to the atmosphere, such as rivers, lakes, reservoirs, ponds, seas, and estuaries.

Surplus Power. The electrical energy from the United States’ share of NGS power that is excess to that used by the Central Arizona Project. This surplus power is sold at market rates with the revenues being deposited to the Lower Basin Development Fund.


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Technical Work Group (TWG). A stakeholder group formed by SRP, comprised of DOI, Gila River Indian Community, Navajo Nation, Salt River Project, Environmental Defense Fund, Central Arizona Water Conservation District, and Western Resource Advocates. The TWG developed an alternative to U.S. Environmental Protection Agency’s proposed BART for NGS, and submitted it for U.S. Environmental Protection Agency’s consideration.

Terrestrial. Relating to land; a land animal.

Threatened Species. Any plant or animal species defined under the Endangered Species Act of 1973 as likely to become endangered within the foreseeable future throughout all or a significant portion of its range. Requirements for declaring a species threatened are contained in the Endangered Species Act of 1973; listings are published in the Federal Register.

Traditional Cultural Property. A cultural property that derives significance from traditional lifeway values associated with it. A traditional cultural property may qualify for the National Register if it meets the criteria and criteria exceptions at 36 Code of Federal Regulations 60.4.

Traditional Use. A term referring to a category that is applied to any cultural resource known to be perceived by a specified social and/or cultural group as important in maintaining the cultural identity, heritage, or well-being of the group. Cultural properties assigned to this category are to be maintained in ways that recognize the importance ascribed to them and seek to accommodate their continuing traditional use.

Tribal Lands. In the Native American Graves Protection and Repatriation Act, tribal land is defined as: (a) all lands within the exterior boundaries of any Indian reservation; (b) all dependent Indian communities; and (c) any lands administered for the benefit of Native Hawaiians pursuant to the Hawaiian Homes Commission Act, 1920, and section 4 of Public Law 86-3. In the National Historic Preservation Act, tribal land is defined as: (a) all lands within the exterior boundaries of any Indian reservation; and (b) all dependent Indian communities.


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Unavoidable Adverse Effects. Effects that cannot be avoided due to constraints in alternatives. These effects do not have to be avoided by the planning agency, but they must be disclosed, discussed, and mitigated, if practicable.


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Visual Resource Management Classes. A classification of landscapes according to the kinds of structures and changes that are acceptable to meet established visual goals.

Visual Resources. The visible physical features of a landscape (topography, water, vegetation, animals, structures, and other features) that constitute the scenery of an area.


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Water Right. A legal entitlement of an individual or entity to extract water from a water source (surface water or groundwater) and to use it for a beneficial use (e.g., potable water supply, irrigation, mining, livestock).

Watershed. 1) A total area of land above a given point on a waterway that contributes runoff water to the flow at that point; 2) A major subdivision of a drainage basin.

Wetlands. Areas characterized by soils that are usually saturated or ponded, i.e., hydric soils, that support mostly water-loving plants (hydrophytic plants).

Wilderness. An area designated by Congress and defined in Section 2(c) of the Wilderness Act of 1964 as an area where the earth and its community of life are untrammeled by man, where man himself is a visitor who does not remain. An area of wilderness is further defined as an area of undeveloped federal land retaining its primeval character and influence, without permanent improvements or human habitation, which is protected and managed so as to preserve its natural conditions and which: 1) generally appears to have been affected primarily by the forces of nature, with the imprint of man’s work substantially unnoticeable; 2) has outstanding opportunities for solitude or a primitive and unconfined type of recreation; 3) has at least 5,000 acres of land or is of sufficient size as to make practicable its preservation and use in an unimpaired condition; and 4) also may contain ecological, geological, or other features of scientific, educational, scenic, or historical values.

Wind Rose. A circular diagram showing, for a specific location, the percentage of the time the wind is from each compass direction. A wind rose for use in assessing consequences of airborne releases also shows the frequency of different wind speeds for each compass direction.

X, Y, Z

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Xeric. An environment or habitat that is extremely dry, lacking humidity and water.

Zone of Saturation. The area in an aquifer, below the water table, in which relatively all pores and fractures are saturated with water. Also called the phreatic zone, it may fluctuate with changes of season and during wet and dry periods. Multiple zones of saturation may occur below any given point on the surface.