Stormwater Words to Know!
Glossary of terms
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
303(d) waterbody - A list of lakes, rivers, and streams that have been designated as impaired or threatened by a pollutant(s) for which one or more TMDLs are needed. Impaired means that the water is not meeting state water quality standards.
319 - The section of the Federal Clean Water Act that deals with nonpoint pollution
Algal bloom – Rapidly occurring growth and accumulation of algae within a body of water, which usually results from excessive nutrients or sluggish circulation within a waterbody. Persistent and frequent blooms can result in low dissolved oxygen in the water which is hazardous to aquatic life.
Aquifer - A water-bearing layer of soil, sand, gravel, or rock that will yield usable quantities of water to a well.
Basin plan - A plan and all implementing regulations and procedures, such as construction projects, public education activities, land use management regulations adopted by ordinance for managing surface and storm water management facilities, and features within individual subbasins.
Benthic- Relating to or occurring at the bottom of an aquatic ecosystem.
Best Management Practice (BMP) – actions, behaviors or on-the ground landscaping practices that reduce pollution and/or the amount of storm water runoff flowing into local waterways. BMPs can be structural, such as a rain barrel or shoreline buffer, or non-structural, such as picking up after your pet or washing your car on the grass.
Biofiltration swale or bioswale - A long, gently sloped, vegetated ditch designed to filter pollutants from stormwater. Grass is the most common vegetation, but wetland vegetation can be used if the soil is saturated.
Bioretention – A water quality practice that uses landscaping and soils to treat stormwater by collecting it in shallow depressions and then filtering it through a planting soil media.
Buffer - An area of trees, shrubs and plants next to a waterbody designed to protect the receiving waterbody from sediment and pollutants contained in storm water runoff. Buffers also function as habitat for migratory birds and aquatic and terrestrial wildlife.
Catch basin - Curbside opening that collects rainwater from streets and serves as an entry point to the storm drain system.
Channel - A long, narrow excavation or surface feature that conveys (or moves) surface water from one area to another and is open to the air.
Chlorine - One of the most common chemicals used in the treatment of public water supplies because it is highly effective in killing harmful microorganisms.
Clean Water Act (CWA) - The Clean Water Act is a 1977 amendment to the Federal Water Pollution Control Act of 1972, which set the basic structure for regulating discharges of pollutants to waters of the
Conservation - Methods of using water wisely with the minimum amount of water being wasted.
Contamination - The introduction of a harmful substance into the water either at the supply or during distribution.
Conveyance - The process of water moving from one place to another.
Cultural eutrophication - Artificial and accelerated aging process of waterbodies. Nutrients like fertilizer enter surface waterbodies causing them to fill with aquatic plants and algae. The increase in plant life creates a biologically productive environment (bacteria can grow,) which reduces the oxygen content of the water. Eutrophic lakes often are undesirable for recreation and may not support normal fish populations.
Culvert -Pipe or concrete box structure which drains open channels, swales, or ditches under a roadway or embankment typically with no catch basins or manholes along its length.
Discharge - The amount of water or substance which flows into a water body from a point or non point source. Wastewater treatment plant discharge means treated sewage discharged from a sewage treatment plant.
Dissolved oxygen - The amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure, often expressed as a concentration in parts of oxygen per million parts of water.
Drainage - The collection, conveyance, containment, and/or discharge of surface and storm water runoff.
Drainage area or drainage basin - An area draining to a point of interest. A area of catchment contributing runoff to the treatment system.
Drought - A period of lower-than-normal precipitation that can lead to a water shortage.
Easement - A right, such as a right-of-way, afforded a person to make limited use of another's real property.
Ecosystem – An interactive system that includes the organisms of a natural community together with their abiotic, physical, chemical and geochemical environment.
Effluent - The discharge of water with a contaminant or contaminants from animal production facilities, industrial facilities or waste water treatment plant.
Effluent limitations - Restrictions imposed on the quantities, discharge rates, and concentrations of pollutants that can be discharged from point sources of pollution into waterways. These restrictions are incorporated into each polluter’s NPDES permit under the Clean Water Act.
Erosion - When land is diminished or worn away due to wind, water, or glacial ice. Often the eroded debris (silt or sediment) becomes a pollutant via stormwater runoff. Erosion occurs naturally but can be intensified by land clearing activities such as farming, development, road-building, and timber harvesting.
Eutrophic - A condition of a water body in which excess nutrients, particularly phosphorous, stimulates the growth of aquatic plant life usually resulting in the depletion of dissolved oxygen. Thus, less dissolved oxygen is available to other aquatic life.
Eutrophication - The aging process of a waterbody. All waterbodies become eutrophic over time when time is measured in hundreds or thousands of years.
Fecal coliform - A portion of the coliform bacteria group originating in the intestinal tract of warm-blooded animals and passes into the environment as feces.
Filtration - The process by which organic and inorganic particles are removed from the raw water.
First flush -The first big rain after an extended dry period (usually summer) which flushes out the accumulated pollutants in the storm drain system and carries them straight to the ocean.
Floodplain – Areas that are periodically flooded by lateral overflow, such as river.
Forebay – Stormwater structural design feature that uses a small basin to settle out incoming sediment delivered in runoff to a stormwater BMP.
Geographic information systems (GIS) – A computer system for capturing, storing, checking, integrating, manipulating, analyzing and displaying data related to positions on the Earth’s surface. Typically, GIS is used for creating or handling maps of one kind or another.
Groundwater - Water that occupies hollows, cracks, or other spaces between particles of clay, silt, sand, gravel or rock within the saturated zone. Water in the saturated zone is the only subsurface water available to supply wells and springs.
Groundwater recharge - The process where water enters the soil and eventually reaches the saturated zone. Recharge varies from place to place due to the amount of rainfall, infiltration, and surface vegetation.
Habitat - The specific area or environment where a plant or animal lives. A habitat must provide all of the basic requirements for life (food, water, shelter) and should be free of harmful contaminants and pollution.
Household hazardous waste - Common everyday products that people use in and around their homes—including paint, paint thinner, herbicides (weed killer), and pesticides—that, due to their chemical nature, can be hazardous if not properly disposed
Hydrologic cycle - Also called the Water Cycle. This is the natural cycle of water, including evaporation, transpiration, condensation, precipitation and percolation.
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Illicit connection - Any discharge to a municipal separate storm sewer that is not composed entirely of stormwater and is not authorized by an NPDES permit, with some exceptions (e.g., discharges due to fire fighting activities).
Illicit discharges - Discharges or dumping of anything that is not stormwater into the storm drainage system. Examples are discharges from floor drains, appliances, industrial processes, sinks, and toilets that are connected to the nearby storm drainage system. These discharges should be going to the sanitary sewer system, a holding tank, an on-site process water treatment system, or a septic system.
Impaired stream/river/waterbody - Waterbodies (i.e., stream reaches or lakes) that have been placed on the Section 303(d) list because they exceed water quality standards for one or more pollutant(s).
Impervious surface - Any surface that water cannot penetrate into (i.e. parking lots, streets, sidewalks, rooftops).
Impoundment - A natural or man-made containment for surface water.
Intake - The part of a surface water treatment facility where water from a lake, river or stream is drawn into the plant for filtration, treatment and distribution to customers.
Maximum Extent Practicable (MEP) - A standard for water quality that applies to all MS4 operators regulated under the NPDES Stormwater Program. Since no precise definition of MEP exists, it allows for maximum flexibility on the part of MS4 operators as they develop and implement their programs.
Municipal Separate Storm Sewer System (MS4) - A publically-owned conveyance or system of conveyances that discharges to waters of the
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National Pollutant Discharge Elimination System (NPDES) - In 1972, the National Pollutant Discharge Elimination System program was established under the authority of the Clean Water Act. It is a national system for issuing, modifying, revoking, monitoring and enforcing permits. NPDES permits regulate point sources and non point sources of pollution. The system also imposes and enforces pretreatment requirements.
Non point source pollution - Water runoff without a single point of origin that flows over the surface of the ground by irrigation water or stormwater and is then introduced to surface or ground waters. NPSs include atmospheric deposition and runoff or leaching from agricultural lands, urban areas, unvegetated lands, onsite sewage treatment and disposal systems, and construction sites.
Nonstructural BMP- A preventative action to protect receiving water quality that does not require construction and include activities such as education, stream watching, adopt a stream programs, recycling, and maintenance practices. Nonstructural BMPs rely on behavioral changes in order to be effective.
NPDES Phase I: Phase I of the NPDES stormwater program was established in 1990 and required NPDES permit coverage for large or medium municipalities that had populations of 100,000 or more. The City of
NPDES Phase II: Phase II of the NPDES Stormwater program was signed into law in December 1999. This regulation requires that smaller communities, also known as small municipal separate storm sewer systems (MS4s), be permitted. Regulated small MS4s applied for permit coverage by March 2003. Those communities permitted under Phase II are required to develop and implement a comprehensive stormwater management program that includes six minimum measures: (1) public education and outreach on stormwater impacts; (2) public involvement/participation; (3) illicit discharge detection and elimination; (4) construction site stormwater runoff control; (5) post-construction stormwater management for new development and redevelopment; and (6) pollution prevention/good housekeeping for municipal operations.
Nutrient - An element or compound essential for animal and plant growth. Common nutrients in fertilizer include nitrogen, phosphorus, and potassium.
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Outfall – Point where water flow from (i.e. conduit, stream, pipe, drain).
Peak flow - The maximum flow that the collection system is designed to handle, typically associated with a recurrence interval (e.g., 10-yr, 25-yr, 50-y or 100-yr).
Pervious materials - Pervious materials allow water to soak into the surface because they are porous.
Phase 1 Stormwater Permit Program - The Phase I program addressed sources of storm water runoff that had the greatest potential to negatively impact water quality. Under Phase I, EPA required NPDES permit coverage for storm water discharges from "medium" and "large" municipal separate storm sewer systems (MS4s) located in incorporated places or counties with populations of 100,000 or more; and eleven categories of industrial activity, one of which is construction activity that disturbs five or more acres of land.
Phase 2 Stormwater Permit Program - The Phase II Program requires NPDES permit coverage for storm water discharges from certain regulated small municipal separate storm sewer systems (MS4s); and construction activity disturbing between 1 and 5 acres of land.
Point source: An identifiable and confined discharge point for one or more water pollutants, such as a pipe, channel, vessel, or ditch.
Pollution - An undesirable change in the physical, chemical, or biological characteristics of air, water, soil, or food that can adversely affect the health, survival, or activities of humans or other living organisms.
Pollution-generating pervious surface - A pervious surface with vegetative ground cover on which pesticides and fertilizers may be used. Such surfaces include, but are not limited to, the lawn and landscaped areas of residential or commercial sites, golf courses, parks, and sports fields.
Potable water - Water that is safe to drink after the raw water has gone through the filtration and treatment process.
Public water supply - Drinking water provided to a group of homes or an entire city through a water utility via underground pipes and water mains.
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Raw water - The water from a surface water or groundwater source prior to filtration or treatment.
Receiving waters - Bodies of water or surface water systems receiving water from upstream man-made or natural systems.
Recharge - The increase in groundwater levels after rainwater soaks into the ground and into the saturated zone.
Recharge area - An area of land that allows rainwater to drain or soak into the earth's surface to replenish groundwater sources.
Reservoirs - Man-made storage areas for water. Sometimes a reservoir will be open, like a man-made lake, or it may be a fully enclosed tank, either above-ground or underground.
Residence time - The length of time that a pollutant remains within a section of a stream or river. The residence time is determined by the stream flow and the volume of the river reach or the average stream velocity and the length of the river reach.
Retention - The process of collecting and holding surface and storm water runoff with no surface outflow.
Riparian - Pertaining to the banks of rivers and streams, and sometimes also wetlands, lakes, or tidewater.
Riprap - A facing layer or protective mound of stones placed to prevent erosion or sloughing of a structure or embankment due to the flow of surface and storm water runoff.
River basin - The land area drained by a major river and its tributaries.
Runoff - Water originating from rainfall and other precipitation that ultimately flows into drainage facilities, rivers, streams, springs, seeps, ponds, lakes, and wetlands as well as shallow groundwater.
Sanitary sewer system - The system that collects and transports sanitary wastewater from building plumbing systems to a wastewater treatment plant for treatment (i.e. wastewater from toilets, showers, sinks, water fountains).
Site Runoff - Any drainage or flood discharge that is released from a specified area.
Storm drainage system - The system built to collect and transport runoff to prevent flooding. This system consists of storm drains, drainage ditches, pipes and culverts. Anything that flows into the storm drainage system flows directly into local creeks and waterways. (Storm water runoff is not treated.) Storm drainage systems are completely separate from those that carry domestic and commercial wastewater (sanitary sewer system).
Stormwater runoff - Precipitation (rain water) or irrigation water that does not infiltrate but flows over the land surface toward a surface drain, eventually making its way to a river, lake or an ocean.
Structural BMP - Constructed facilities or measures to help protect receiving water quality and control stormwater quantity. Examples include storage, vegetation, infiltration, and filtration.
Subbasin - A drainage area which drains to a river which is part of a larger drainage basin or area. A subdivision of a larger river basin.
Surface water - Any source of water that is found on top of the earth's surface, such as a lake, river or stream.
Swale - A shallow drainage conveyance with relatively gentle side slopes, generally with flow depths less than one foot.
Total Maximum Daily Load (TMDL) - The maximum amount of pollutants which can released into a water body without hurting the water quality.
Toxic substances – Those chemical substances, such as pesticides, plastics, heavy metals, detergents, solvents, or any other harmful materials, which are poisonous, carcinogenic, or otherwise directly harmful to human health and the environment.
Treatment - The process by which substances are added to the water in order to make it safe to drink or look and taste better.
Tributary - A stream that flows into a larger stream or other body of water.
Turbidity – Having sediment or foreign particles stirred up or suspended in water; muddy.
Urban Runoff - Stormwater from urban areas, which tends to contain heavy concentrations of pollutants from urban activities.
Urbanized Area (UA) - A Bureau of the Census determination of a central place (or places) and the adjacent densely settled surrounding territory that together have a minimum residential population of 50,000 people and a minimum average density of 1,000 people/square mile. This is a simplified definition of a UA, the full definition is very complex.
Wastewater treatment plant - A facility with a series of tanks, screens, filters, and other processes used to clean wastewater before it is returned to the environment.
Water meter - A device that records the amount of water being used in your home.
Water Quality Criteria - Specific levels of water quality that, if achieved, are expected to render a body of water suitable for its designated use. The criteria are based on specific levels of pollutants that would make the water harmful if used for drinking, swimming, farming, fish production, or industrial processes.
Watershed - Also called a drainage basin. This is an area of land that allows rainwater to flow into creeks, streams and rivers. Watersheds range in size from a few acres to large areas of the country. Large watersheds are sometimes referred to as river basins or sub basins.
Wetland - An area inundated or saturated by ground or surface water 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 (U.S. Army Corps of Engineers Regulation 33 CFR 328.3 (1988)).
Wetlands Protection - Activities to protect and restore wetlands that are an integral part of a nonpoint source management program or part of implementation or development of comprehensive estuary conservation and management plans.