Watershed Academy Web


10 C - (see Primary contact recreation)

1Q10 - Lowest (or highest) 1-day average stream flow that occurs once in 10 years, on average.

20 C - (see Secondary contact recreation)

303(d) list - A list of waters that fail to meet any applicable water quality standards, that states are required, under sec. 303(d) of the CWA, to assemble and update once every 2 years. EPA is required to determine the completeness of such lists.

305(b) report - State-prepared reports describing what is known about the condition of the waters within each state. Required under section 305(b) of the CWA, these reports, must be submitted to EPA on April 1st of even-numbered years.

319 program - Under section 319 of the CWA, EPA provides grants to states to enable them to develop and implement programs to address the effects of nonpoint source pollution.

401 Certification - According to section 401 of the CWA, a federal agency cannot issue a license or permit to an activity affecting a waterbody unless the state water quality agency certifies that the activity would not cause failure to meet any state water quality standard applicable to said waterbody.

404 Program - Established by section 404 of the CWA, this program regulates the placement of dredged and fill material in surface waters falling within the jurisdiction of the CWA.

7Q3 - Lowest (or highest) 7-day average stream flow that occurs once in 3 years, on average.

7Q10 - Lowest (or highest) 7-day average stream flow that occurs once in 10 years, on average.

Advanced wastewater treatment - Any treatment of sewage that goes beyond primary (see definition below) and secondary (see definition below), which may include treatment specifically designed to remove nitrogen and/or phosphorous.

Ambient monitoring - The systematic, long-term assessment of pollutant levels by measuring the quantity and types of certain pollutants in the water or surrounding environment.

Antibacksliding - A provision in EPA regulations specifying that a reissued NPDES permit must be no less stringent than the previous permit, except in certain limited conditions.

Antidegradation - Requirements established in the CWA and EPA regulations designed to prevent, or at least minimize, deterioration of water quality. States must adopt both an antidegradation policy and implementation methods. (Not to be confused with "antibacksliding," above)

Animal feeding operation (AFO) - Agricultural facilities where animals are confined and fed or maintained for a total of 45 days or more in any 12-month period, and crops, vegetation, forage growth, or post-harvest residues are not sustained in the normal growing season over any portion of the lot or facility. Unlike pasturing and grazing operations, AFOs confine animals at densities high enough that no vegetation of any type is sustained within the facility.

Background condition - Some aspect of the environment that is outside the temporal and/or spatial extent of a particular situation. Background conditions can be either natural (see also "natural background condition") or man-made (anthropogenic). With regard to anthropogenic conditions, "background" can be either controllable or essentially uncontrollable, in a technological or legal context.

Best available technology (BAT, BATEA) - One of several types of EPA-issued, technology-based regulations for controlling the direct discharges of pollutants to surface waters under jurisdiction of the CWA. BAT limits represent the best existing treatment technologies that are economically achievable within an industrial point source category or subcategory. BAT applies to older industrial facilities; newer facilities are covered by another set of EPA regulations new source performance standards (NSPS).

Best management practice (BMP) - Schedules of activities, prohibitions of practices, maintenances procedures, and other management practices other than traditional physical, chemical, or biological wastewater treatment. BMPs can be either nonstructural (good housekeeping practices, pollution prevention, contour plowing, cover crops) or structural (wet or dry detention ponds), and can include treatment requirements, operating procedures, and practices to control site runoff, spillage, or leaks. BMPs can be applied to both nonpoint and point sources of water pollution and can be employed as part of either regulatory or voluntary programs.

Bioaccumulation - Processes whereby the concentration of pollutants in living organisms are elevated to levels substantially higher than that in the aquatic environment.

Bioaccumulative pollutant of concern (BCC) - Contaminants that tend to bioaccumulate to a high degree. Examples include mercury, PCBs, and DDT.

Bioconcentration - A type of bioaccumulation that occurs directly across cell membranes that come in direct contact with contaminated water but is not further increased by passage of contaminants up a food chain.

Biomagnification - A type of bioaccumulation in which the level of a contaminant increases by a substantial amount as it is passed through each step in a food chain or web.

BOD - Biochemical oxygen demand. A measurement of the amount of oxygen consumed by the decomposition of organic material over a certain period of time. For instance, BOD5 is based on the amount of oxygen consumed over 5 days.

CFS - Cubic feet per second.

Chemical Oxygen Demand - A measure of the oxygen-consuming capacity of inorganic and organic matter present in wastewater. COD is expressed as the amount of oxygen consumed in a given period of time. (see also BOD)

Clean Water Act - Common name for the Federal Water Pollution Control Act of 1972, which restructured and expanded the federal government's authority for water pollution control and consolidated authority in the Administrator of the Environmental Protection Agency.

COD - Chemical oxygen demand.

Code of Federal Regulations (CFR) - A set of documents containing all regulations issued by federal agencies. Environmental regulations, including those issued by EPA pertaining to the CWA are found in Chapter 40 of the code.

Combined sewer overflow (CSO) - Precipitation-induced overflow from systems designed to collect domestic sewage, industrial wastewater and stormwater runoff in the same set of pipes. (See also "MS4s" and "sanitary sewer system.")

Concentrated animal feeding operation (CAFO) - An animal feeding operation defined as a point source of pollutants. CAFOs are generally larger AFOs, and categorized by the number of animals present, but they can also include smaller AFOs known to be discharging pollutants to surface waterbodies at levels of concern. CAFOs are covered under the NPDES permit program (see below), while AFOs are not.

Contiguous zone - The entire zone established by the United States under article 24 of the Convention of the Territorial Sea and the Contiguous Zone.

Criterion (see Water Quality Criteria).

Criterion-concentration - The component of a water quality criterion that specifies a maximum or minimum concentration of a water quality parameter. (see also criterion-magnitude)

Criterion-digression - A situation in which the level of a water quality parameter in a waterbody has risen for at least a moment, to a level above (or where relevant below) the level specified by an applicable water quality criterion.

Criterion-duration - The component of a water quality criterion that specifies a minimum time frame over which the average level of a water quality parameter should not surpass the criterion-magnitude (concentration). Criterion-durations are often referred to as criterion averaging periods.

Criterion-exceedance - A situation in which conditions in a waterbody are worse than those described by the criterion-magnitude (concentration), criterion-duration, and criterion-frequency of an applicable water quality criterion. For example, if a WQC for a certain pollutant is expressed as "the 30-day average waterbody concentration must not go above 25 μg/L more than once in 365 days," a criterion-exceedence would have occurred in a waterbody if the average ambient concentration of the pollutant to which the criterion applies went above 25 μg/L, for 2 or more 30-day periods in a given 365-day period.

Criterion-excursion - A situation in which conditions in a waterbody are worse than those described by the criterion-magnitude (concentration) and criterion-duration of an applicable water quality criterion. For example, if a WQC for a certain pollutant has a criterion-concentration of 25 μg/L and a criterion-duration of 30 days, any period in which the 30-day average concentration of that pollutant in a waterbody had gone above 25 μg/L would be a criterion-excursion.

Criterion-frequency - The component of a water quality criterion that specifies the maximum rate at which criterion-excursions can occur without having a criterion-exceedance. For example, a criterion-frequency might specify that the 30-day average concentration of a pollutant should not surpass 25 μg/L more than once in any 365-day period.

Criterion-magnitude - The component of a water quality criterion that specifies a maximum or minimum level of a water quality parameter. Usually expressed as a concentration (see criterion-concentration), but for some parameters (pH, temperature, turbidity, etc.) it is expressed in other terms.

Critical conditions - Those circumstances in which, because of a variety of factors, adverse effects on the environment and/or human health are likely to occur at a given site.

Cost-benefit analysis - A calculation of the monetary costs of a given action (e.g., regulation, infrastructure project) compared to the monetized benefits. In the environmental context, changes in environmental conditions and effects (aesthetics, populations of plants and animals, ecosystem functions, human health impacts) must be somehow converted to a monetary form.

Cost-effectiveness analysis - A calculation of the monetary cost of achieving a certain amount of a given desired outcome. In the environmental context, this involves estimating the cost of reducing loadings of a given unit of pollutants to the environment (e.g., dollars per pound). Technology-based effluent limits (see definition below) established under the CWA are based on cost-effectiveness analysis.

CWA - Abbreviation for the federal Clean Water Act, also known as the Federal Water Pollution Control Act of 1972, which restructured the authority for water pollution control and consolidated authority in the Administrator of the Environmental Protection Agency.

CWSRF - The Clean Water State Revolving Loan Fund, under which the federal government provides capitalization grants to states for establishment and expansion of revolving loan funds whereby municipalities and certain private entities can obtain funding for various types of clean water-related projects. (see also DWSRF)

Designated use (DU) - A use that state and federal governments have determined should be attained in a given waterbody, regardless of whether the waterbody could support the use at the time of designation. Examples include (1) support of aquatic life, (2) body contact recreation, (3) fish consumption, and (4) public drinking water supply.

Design conditions - A specific set of circumstances for which an NPDES permit, TMDL, set of best management practices, or some sort of watershed plan is designed to meet applicable water quality standards (WQS). For example, NPDES permit limits are often designed to result in attainment of WQS in a receiving stream whenever the stream flow is higher than a defined low flow (e.g., 7Q10 - see definition above).

Design flow - A type of design condition that refers to a specific stream flow.

Digression - (see criterion-digression)

DO - Dissolved oxygen. The concentration of oxygen dissolved in water, expressed in milligrams per liter or percent saturation.

DWSRF - The Drinking Water State Revolving Loan Fund created by the federal Safe Drinking Water Act (SDWA), under which the federal government provides capitalization grants to states for establishment and expansion of revolving loan funds whereby drinking water utilities can obtain funding for various types of clean drinking water-related projects. (see also CWSRF)

Effects-based water quality criterion - A WQC expressed in terms of effects on aquatic ecosystems or humans, as opposed to levels of pollutants or other stressors. Examples of response indicators for which effects-based WQC have been established include dissolved oxygen, pH, temperature, turbidity, chlorophyll a, and the structure or function of aquatic communities.

Effluent - Wastewater discharged from an industrial facility, sewage treatment plant, or other point source discharge (see definition below).

Effluent limit/limitation - A restriction on quantities, discharge rates, and concentrations of pollutants (chemical, physical, biological) discharged from a point source into surface waters under the jurisdiction of the CWA. Effluent limits are set forth as enforceable requirements in NPDES permits.

Ephemeral - A stream or portion of a stream that flows briefly in direct response to precipitation in the immediate vicinity, and whose channel is at all times above the groundwater reservoir.

Existing use - According to EPA regulations governing state water quality standards, any use that has been attained at any time since November 28, 1975. In this context, "attained" means that the use took place and/or water quality adequate to support the use occurred.

Feeding (trophic) guild - A group of organisms that is similar in its nutritional requirements and feeding habits, such as planktivores, piscivores, omnivores, etc.

"Fishable/swimmable" goal - An abbreviation of the language set forth in section 101(a) of the CWA, which states that where achievable, water quality sufficient to support protection and propagation of fish, shellfish, and wildlife and recreation in and on the water shall be attained by 1985.

Generalists - Organisms that are tolerant of variable environmental conditions. Generalists are typically able to accommodate multiple prey types and thrive under variable or unpredictable environmental conditions.

General permit - With regard to both the CWA 402 (NPDES) and 404 permit programs, a permit authorizing specified discharges of pollutants to waters of the United States from more than one source or activity. General permits apply to similar sorts of sources/activities taking place within a specified geographic area. Essentially the same requirements apply to all sources covered by a given general permit.

Indirect discharger - An facility that, instead of discharging pollutants or wastewater directly into a water of the United States, sends them into a municipal sewer system. Though not covered by the CWA's NPDES program, indirect discharges of toxic chemicals from industrial operations are subject to the CWA's pretreatment program (see below).

LC50 - Lethal concentration for 50 percent of organisms exposed to a chemical or other stressor over a specified period (e.g. 96 hour LC50).

Load allocation (LA) - That portion of a waterbody's loading capacity for a given pollutant established in a TMDL assigned to nonpoint sources. Anticipated future loads of pollutants from nonpoint sources can be included as a specific suballocation of under the LA, or can be included in separate "growth allocation" or "reserve capacity".

Loading capacity - For a given waterbody, the maximum pollutant-specific loading rate consistent with attainment of a particular water quality standard.

Margin of safety (MOS) - In the context of the TMDL program, a safety factor applied to a waterbody-pollutant specific loading capacity estimates, to ensure attainment of water quality standards.

Maximum contaminant level (MCL) - Limits on levels of contaminants in finished drinking water, set by EPA under the SDWA. (Contrary to their name, MCLs typically do not set limits on instantaneous maximum levels of contaminants/pollutants but are typically expressed as annual average maximum concentrations.)

Maximum extent practicable (MEP) - Technology-based NPDES permit limits applicable to municipal separate stormwater sewer systems (MS4s). EPA specifies that compliance with MEP can be attained by developing a stormwater management plan that addresses the six minimum control measures described in the stormwater regulations.

MCL - Maximum contaminant level (see definition above)

mgd - Million gallons per day

Minimally impaired - Describes the condition of the biota and habitat in an ecosystem having minimal influence from human activities. Minimally impaired habitats achieve biological integrity.

Mixing zone - An area in a receiving waterbody where effluents from a point source discharge undergoes initial dilution in which some, or all, otherwise applicable water quality criteria do not apply.

MS4 - Municipal separate storm sewer system. A system of pipes and other conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains) that collects and conveys only urban stormwater runoff and discharges it directly to one or more waters falling under the jurisdiction of the CWA. By definition, MS4s are owned or operated by a state, city, town, county, district, association, or other public body (see also "combined sewer system CSO" and "sanitary sewer system")

Municipal separate storm sewer system (see MS4, above).

Natural background condition - Characteristics of a waterbody in the absence of any pollutants or other anthropogenic stressors.

Narrative water quality criteria - A description of acceptable waterbody conditions contained in state water quality standards expressed without use of numbers. For example, "no excess plant growth" or "waterbodies must be free from floating scum or sludge".

Navigable waters - A term sometimes used to describe those surface waters falling under the jurisdiction of the CWA. (see also "traditional navigable waters")

NOI - Notice of intent that is typically sent to a regulatory authority to apply for coverage under a general permit. Most general NPDES (CWA section 402) and U.S. Army Corps of Engineers "dredge and fill" nationwide or regional permits (CWA section 404) permits require that discharges from a pollutant source must submit a written NOI to the relevant permitting authority.

Nonpoint source (NPS) - A diffuse source of water pollution that is not collected and discharged through a discrete man-made conveyance. (i.e, any source of pollutants not considered a point source under the CWA.) Atmospheric deposition and hydromodification are also nonpoint sources of pollution.

NPDES - National Pollutant Discharge Elimination System. A CWA-established national program regulating direct discharges of pollutants from point sources to the waters falling under the jurisdiction of the CWA.

Numeric water quality criteria - Descriptions of acceptable waterbody conditions contained in state water quality standards regulations that are expressed in numeric (as opposed to purely narrative) form. Numeric criteria consist of three basic elements: (1) a criterion-concentration (or magnitude in the case of parameters like temperature and pH); (2) a criterion-duration (sometimes called criterion-averaging period); and (3) a criterion-frequency (sometimes called a recurrence interval).

Ocean - Any portion of the high seas beyond the contiguous zone.

Outfall - A place where wastewater or stormwater, or a combination thereof, is discharged into a waterbody via a point source.

Point source - A discernable, discrete, confined man-made conveyance whereby pollutants are discharged directly to surface waters falling under the jurisdiction of the CWA. Such conveyances include pipes, ditches, channels, tunnels, conduits, wells, discrete fixtures, containers, rolling stock (wheeled vehicles),concentrated animal feeding operations, landfill leachate collection system, and vessels and other floating craft.

Pollutant - Industrial, municipal, and agricultural waste, including sewage, chemical wastes, dredged spoil, sand, sewage sludge, solid waste, garbage, rock, heat, filter backwash, discarded equipment, munitions, and radioactive and biological materials discharged into water.

Pollution - The man-made or man-induced alteration of the chemical, physical, biological, and radiological integrity of water.

Precipitation-dependent source - (see also "wet weather point source") A source of pollutants that loads pollutants into waterbodies only as a result of runoff resulting from precipitation events (rain, snow). Such sources can be considered, under the CWA, as either nonpoint or point sources, depending on whether the runoff and associated pollutants are collected into a man-made conveyance (point source) or enter the waterbody in a diffuse manner (nonpoint source). Row crop farming and livestock pasturing/grazing are examples of nonpoint sources. MS4s, CSOs, CAFOs, and some road systems and construction sites are examples of precipitation-dependent point sources.

Precipitation-independent source - A source that loads pollutants into waterbodies regardless of whether precipitation events have occurred. Examples include municipal sewage treatment plants and industrial process dischargers.

Pretreatment program - Applicable to indirect industrial dischargers (see definition above), this program sets technology-based limits on levels of toxic pollutants in wastewater from such facilities that are discharged into municipal sewer systems.

Primary contact recreation - Forms of water-based recreation in which the intake of pathogens and other contaminants found in ambient water is a reasonable possibility, due to ingestion of, and/or exposure of pervious membranes to, surrounding water.

Primary drinking water standard - A health-based limit on levels of contaminants in finished drinking water established under the federal Safe Drinking Water Act. (see also "maximum contaminant level-MCL")

Primary treatment - Treatment of wastewater by removing solids and organic matter, employing physical means such as screens, filters, and settling basins.

Process wastewater - Pollutant-carrying water resulting from contact with materials used in industrial manufacturing processes.

PS - Point source (See definition above)

Publicly owned treatment works (POTW) - A sewer collection and treatment system owned by a municipality or a state. Includes sewers, pipes, conveyances, and devices and systems used to store, treat, recycle, and reclaim sewage or industrial wastewater.

PWS - In the context of WQS established under the CWA, "public water supply," which refers to a waterbody used as a raw water source by a drinking water utility. In the context of the Safe Drinking Water Act, a "public water system.

Reference condition - Ideally, reference conditions represent the highest biological conditions found in waterbodies undisturbed by anthropogenic stressors. Acceptable reference conditions will differ between geographic regions and states. Reference conditions can be derived from reference sites, an empirical model of expectations that can include knowledge of historical conditions, or a model extrapolated from ecological principles. Usually, data from sites that represent best attainable conditions (i.e., least disturbed) of a waterbody are used.

Response indicator - A characteristic of a living system that reflects the effect of one or more stressors. Commonly used examples in the context of the CWA include depleted populations of aquatic organisms, unnaturally low or high pH, temperature, or dissolved oxygen, increased chlorophyll a, and increased turbidity.

Sanitary sewer system - A system of pipes and other conveyances that collects and carries waste from homes, offices, industrial facilities, and other kinds of buildings and operation to a municipal sewage treatment facility. Sanitary sewers to not carry urban stormwater runoff. (see also "MS4s" and "CSOs".)

Secondary contact recreation - Forms of water-based recreation in which contact with surrounding water is unlikely, such as fishing and motor boating.

Secondary drinking water standard - A limit on levels of contaminants in finished drinking water established under the federal Safe Drinking Water Act that addresses the aesthetic aspect of drinking water, such as color and odor.

Secondary treatment - Treatment of wastewater employing a combination of physical and biological processes, such as "activated sludge". Refers specifically to wastewater treatment requirements applying to discharges of BOD5, total suspended solids (TSS), and pH from municipal sewage treatment facilities.

Sewage treatment plant (STP) (see "Publicly owned treatment works")

Specialists - Organisms that have special nutritional needs or other physiological or physical requirements and live in a restricted habitat that provides those needs.

SRF - State revolving loan fund.(see CWSRF and DWSRF)

Standard - In the context of the Clean Water Act, a term used to refer to a number of different requirements and/or threshold levels, including water quality standards, water quality criteria, criterion-concentrations, effluent limitations, technology-based regulations applicable to point sources. It can also include primary and secondary drinking water standards established under SDWA.

TDS - Total dissolved solids. A measure of organic and inorganic substances suspended in water in molecular, ionized, or colloidal form.

Technology-based approach - An approach to environmental management whereby limits on releases of stressors into the environment are established according to cost-effectiveness analyses (see definition above). Examples of such requirements are BAT for industrial sources, secondary treatment for POTWs, and MEP for municipal separate storm sewers. Currently, best management practices applied to wet-weather point and nonpoint sources are typically based on the technology-based approach; although, they can be employed in a water quality-based approach.

Technology-based effluent limits (TBELs) - Technology-based limits on discharges of pollutants from point sources to waters of the United States set forth in NPDES permits, usually based on the capability of a treatment method to reduce pollutant levels to a certain concentration or mass loading level.

Territorial seas - The belt of the seas measured from the line of ordinary low water along that portion of the coast that is in direct contact with the open sea and extending seaward a distance of 3 miles.

TMDL Implementation Plan - Once a TMDL is developed and approved by EPA, measures described in the TMDL are taken to reduce pollution levels in the stream. Such measures are described in a TMDL Implementation Plan.

Total Maximum Daily Load (TMDL) - A calculation of the maximum amount of a pollutant that a waterbody can receive and still safely meet water quality standards.

Traditional navigable waters - Waters defined as navigable before passage of the CWA and their tributaries, including interstate waters, intrastate lakes, rivers, and streams used for recreational or other purposes; and intrastate lakes, rivers, and streams from which fish or shellfish are taken and sold in interstate commerce.

Trophic level - An organism's position in a food chain. The levels are numbered according to how far organisms are along the chain from the primary producers (plants) at level 1, to herbivores (level 2), to predators (level 3), to carnivores or top carnivores (level 4 or 5).

TSS - Total suspended solids. A measure of filterable material suspended in water.

Urbanized area - A land area comprising one or more places - central place(s) - and the adjacent densely settled surrounding area - urban fringe - that together have a residential population of at least 50,000 and an overall population density of at least 1,000 people per square mile.

Use attainability analysis (UAA) - A structured scientific analysis whereby states can determine whether an unattained waterbody use is technologically and economically achievable. To remove a designated use from application to a waterbody, a state must find that, according to a UAA, the unattained use is not attainable within the foreseeable future. Such findings, and the resulting change in designated uses, must be made available for public review and comments, and like any change in WQS regulations, must be approved by EPA to become effective under the CWA.

Wasteload allocation (WLA) - That portion of a waterbody's loading capacity for a given pollutant established in a TMDL assigned to point sources. Anticipated future loads of pollutants from point sources can be included as a specific suballocation under the WLA, or can be included in separate "growth allocation" or "reserve capacity".

Wastewater treatment plant (WWTP) - (see "Publicly owned treatment works")

Water quality-based approach - The application of the "risk-based approach" in the manner specified in the CWA. In particular, the water quality based approach requires setting regulatory limits and applying voluntary programs in a manner to ensure attainment of applicable WQS.

Water quality based effluent limit (WQBEL) - Limits on discharges of pollutants from point sources calculated to ensure attainment of water quality standards in the waterbodies receiving such discharges. Such limits must be included in NPDES permits, where necessary.

Water quality criteria (WQC) - The minimum conditions that a waterbody must attain or maintain to support a designated use. WQC describe physical, chemical, and biological attributes. WQC can be expressed in either numeric or narrative form.

Water quality criterion - The singular of water quality criteria.

Water quality limited segment - A waterbody that fails to meet one or more applicable water quality standards. The section 303(d) list is comprised of water quality limited segments (WQLS).

Water quality standard (WQS) - State-adopted and EPA-approved ambient standards for waterbodies. The standards prescribe the use of the waterbody and establish the water quality criteria and antidegradation measures that must be met to protect designated uses.

Waters of the United States - Waters used in or supporting interstate or foreign commerce or recreation, waters used for interstate or foreign industrial purposes, interstate waters and wetlands, the territorial sea, and the tributaries of and wetlands adjacent to those waters. This term is often used to describe those waters falling under the jurisdiction of the CWA.

Wet-weather point source - (see "precipitation-dependent source")

Wetland - For regulatory purposes under the Clean Water Act, the term wetlands means those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas.