Glossary of Common Stormwater Terms

Earth refilling a trench or an excavation

An earthen mound used to direct flow of runoff around or through a structure.

Best Management Practices (BMPs)
Good housekeeping solutions that include the proper handling, storage, and disposal of toxic materials to prevent stormwater pollution.

Buffer strip or zone
Strip of erosion-resistant vegetation between a waterway and an area of more intensive land use.

Catch Basin
Curbside opening that collects rainwater from streets and serves as an entry point to the storm drain system.

Clean Water Act (CWA) (33 U.S.C. 1251 et seq.)
Requirements of the NPDES program are defined under Sections 307, 402, 318 and 405 of the CWA.

Any pipe for collecting and directing storm water.

Conveyance system
Any channel or pipe for collecting directing storm water.

Construction General Permit
A National Pollutant Discharge Elimination System (NPDES) permit issued by the State Water Resources Control Board for the discharge of storm water associated with construction activity from soil disturbance o five (5) acres or more.

A covered channel or a large-diameter pipe that directs water flow below ground level.

Land stripped of vegetation or land that has had its vegetation worn down due to the impacts from the elements or humans.

The release of storm water or other substance from a conveyance system or storage container

The wearing away of land surface by wind or water. Erosion occurs naturally from weather or runoff but can be intensified by land-clearing practices related to farming, residential or industrial development, road building, or timber-cutting.

The process of removing earth, stone, or other materials, usually by digging.

Filter fabric
Textile of relatively small mesh or pore size that is used to (a) allow water to pass through while keeping sediment out (permeable), or (b) prevent both runoff and sediment from passing through (impermeable).

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.

The cutting and/or filling of the land surface to a desired slope or elevation.

The edge of a street (below the curb) designed to drain water runoff from the streets, driveways, parking lots, etc. into catch basins.

Hazardous substance
1. Any material that poses a threat to human health and/or environment. Typical hazardous substances are toxic, corrosive, ignitable, explosive, or chemically reactive. 2. Any substance named by EPA to be reported is a designated quantity of the substance is spilled in the waters of the United States or if otherwise emitted into the environment.

Household hazardous waste
Common everyday products that people use in and around their homes - including paint, paint thinner, herbicides, and pesticides - that, due to their chemical nature, can be hazardous if not properly disposed. Illegal discharge Any activity or event which results in a release, leak, flow, escape or the placement of any material other than rain water (including liquids or solids) into the storm drain system.

Illicit connection
Any connection to the storm drain system that is not permitted: or any legitimate connection that is used for illegal discharge. Inlet An entrance into a ditch, storm drain, or other waterway.

Material storage areas
On site locations where raw materials, products, final products, by-products, or waste materials are stored.

Non-point source pollution
Pollution that does not come from a single, identifiable source. Includes materials that wash from roofs, streets, yards, driveways, sidewalks and other land areas. Collectively, this is the largest source of stormwater pollution.

Non-storm water discharge
Any discharge to municipal separate storm sewer that is not composed entirely of storm water. Discharges containing process wastewater, non-contact cooling water, or sanitary wastewater are non-storm water discharges.

Notice of Intent (NOI)
A formal notice to the State Water Resources Control Board (SWRCB) submitted by the owner/developer that a construction project is about to begin. The NOI provides information on the owner, location, type of project, and certifies that the permittee will comply with the conditions of the construction general permit.

Notice of Termination (NOT)
Form to notify authorities when a construction project is complete.

NPDES Permit
An authorization, license, or equivalent control document issued by EPA or an approved State agency to implement the requirements of the NPDES program.

Oil sheen
A thin, glistening layer of oil on water.

Organic pollutants
Substances containing carbon which may cause pollution problems in receiving waters.

Organic solvents
Liquid organic compounds capable of dissolving solids, gases, or liquids.

A flow of water from one drainage system into a larger system, or into a body of water like a lake, bay, or the ocean.

The quality of a soil that enables water or air to move through it. Usually expressed in inches/hour or inches/day.

Point-source pollution
Pollution from a single identifiable source such as a factory or a sewage-treatment plant. Most of this pollution is highly regulated at the state and local levels.

Generally, any substance introduced into the environment that adversely affects the usefulness of a resource.

Any form of rain or snow.

The storage of storm water to prevent it from leaving the development site; may be temporary or permanent

Off-site flows which flows onto your site.

Water originating from rainfall and other sources (e.g., sprinkler irrigation) that is found in drainage facilities, rivers, streams, springs, seeps, ponds, lakes, wetlands, and shallow groundwater.

The erosive and digging action in watercourse by flowing water.

Secondary containment
Structures, usually dikes or berms, surrounding tanks or other storage containers and designed to catch spilled material from the storage containers.

The process of depositing soil particles, clays, sands, or other sediments that were picked up by runoff.

Soil, sand, and minerals washed from land into water usually after rain, that pile up in reservoirs, rivers, and harbors, destroying fish-nesting areas and clouding the water so that needed sunlight might not reach aquatic plants. Careless farming, mining, and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Significant materials
Include, but not limited to, raw materials; fuels; materials such as solvents, detergents, and plastic pellets; finished materials such as metallic products; raw materials used in food processing or production; hazardous substances designed under Section 101(4) of CERLCA; any chemical the facility is required to report pursuant to Section 313 of Title III or SARA; fertilizers; pesticides; and waste products such as ashes, slag and sludge that have the potential to be released with storm water discharges.

Significant quantities
The volume, concentrations, or mass of a pollutant in storm water discharge that can cause or threaten to cause pollution, contamination, or nuisance, that adversely impact human health or the environment, and cause or contribute to a violation of any applicable water quality standards for the receiving water.

Source control
Action to prevent pollution where it originates.

Source control BMPs
Everyday operational practices that prevent pollution by reducing potential pollutants at the source.

Spill guard
A device used to prevent spills of liquid materials from storage containers.

Storm drain system
A vast network of pipes and open channels designed for flood control, which discharges straight to the ocean.

Rainwater that enters the storm drain system and empties into lakes, rivers, streams or the ocean.

Stormwater pollution
Water from rain, irrigation, garden hoses or other activities that picks up pollutants (cigarette butts, trash, automotive fluids, used oil, paint, fertilizers and pesticides, lawn and garden clippings and pet waste) from streets, parking lots, driveways and yards and carries them through the storm drain system and straight to the ocean.

An area of land that drains water or runoff to a single point. For example, the watershed of the Ventura River would be the surrounding neighborhoods and natural terrain.