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  • Writer's pictureNadean Carson

Stormwater Terms to Know

We developed this list in conjunction with Space to Build. Please go check out their website and podcast for so much more information!

  1. Stormwater - Water from rainfall and snow that runs off surfaces such as rooftops, paved streets, highways, and parking lots and flows into surface waters, like creeks, rivers and lakes. The important thing to know is that this water is typically NOT treated at a water treatment plant, and goes directly into our waterways.

  2. Construction General Permit - A permit that authorizes the discharge of stormwater from construction sites that disturb one acre or more of land, and from smaller sites that are part of a larger, common plan of development.

  3. Stormwater Pollution Prevention Plan (SWPPP) - A site-specific, written document developed to identify potential sources of stormwater pollution at a construction site, as well ways of reducing pollutants in stormwater discharges from the site. This plan is a living document and must be updated throughout the process of construction.

  4. Storm Drain System - The system of gutters, pipes, streams, or ditches used to carry surface and stormwater from surrounding lands to creeks, streams, lakes, and rivers. It is the super-highway system that precipitation uses to go from the pavement to the waterways.

  5. Stormwater Management - The application of site design principles and construction techniques to prevent sediment and other pollutants from entering waterways. It can include keeping potential pollutants at their source (like dry cement protected in a waterproof container), to treating runoff to capture the pollutant before it gets into the waterway.

  6. Stormwater Pollution - Anything in our stormwater that makes it unclean. The potential pollutants can include anything from soil (sediment), pesticides, litter, oil, grass clippings, tree leaves, bacteria, or anything that you don’t want to swim with.

  7. Best Management Practice (BMP) - A Best Management Practice is a behavior or action that a person performs that protects the health of the environment. Constructed facilities or measures to help protect receiving water quality and control stormwater quantity. Examples include storage, vegetation, infiltration, and filtration.

  8. Sediment - Fancy word for dirt or soil. Sediment typically refers to eroded soil, but can also be dirt from rooftops or paved surfaces. Sediment is an issue when it enters stormwater, and is deposited into our waterways.

  9. Erosion and Sediment Control (ESC) - The practice of preventing or reducing the movement of sediment from a site during construction through the implementation of man-made structures, land management techniques, or natural processes. You want to prevent erosion first, then control sediment secondary.

  10. Bioretention Pond (or Rain Garden) - A stormwater management system that uses special soil and plants to allow stormwater to collect and absorb back into the soil. This reduces the volume of surface water runoff and also captures pollutants.

  11. Drainage Basin - Any area draining to a point. For example, when you look at a site, anywhere that a rain drop can hit the ground and potentially travel to that area. This is used to determine how much stormwater will flow to specifically designed stormwater management systems.

  12. Inlet (Catch Basin) - An underground structure that receives stormwater. It is often concrete and is the area where water enters the storm system. This can include curb inlets, drop inlets, or other structures that accumulate stormwater into the system.

  13. Outlet Protection - A channel lining, structure, or flow barrier designed to lower excessive flow velocities from pipes and culverts, prevent scour, and dissipate energy. Most often you will see large stone placed where stormwater exits a pipe. This stone (provided it is large enough to not get washed away) takes some of the power out of the water and reduces erosion in that area and down the culvert.

  14. Construction Entrance (or Construction Exit, which I like better!) - A temporary stone-stabilized area (or manufactured device) located at the points where vehicles depart the site. The purpose of construction entrances/exits is to provide an area to knock the mud off of wheels, and keep it off public roads.

  15. Detention Pond - Constructed depressed area (pond) where stormwater runoff is accumulated and allowed to runoff slower than it accumulates. The point is to temporarily hold the stormwater and slowly release it. This helps downstream areas from being flooded.

  16. Retention Pond - Constructed depressed area (pond) where stormwater runoff is accumulated and held without being released. These are sometimes referred to as “wet ponds”

  17. Discharge - Runoff, not including offsite flows, leaving the proposed development through overland flow, built conveyance systems, or infiltration facilities.

  18. Erosion - The process that moves material, especially soil, from one location to another. It is caused by the action of wind, water, ice, or other forces working on the Earth's surface. Runoff water increases erosion.

  19. Groundwater - Water that exists underground in the cracks and spaces in soil, sand, and rock. Groundwater is usually stored in aquifers and originates from infiltration. Much of the water used for drinking and irrigation comes from groundwater.

  20. Impervious Surface - Any surface that water cannot soak into such as streets, sidewalks, driveways, rooftops, and compacted soils. Urban areas have lots of impervious surfaces, so there is more stormwater runoff. Common impervious surfaces include rooftops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, and packed gravel roads.

  21. Infiltration - Process of moving water into the soil from the surface, the focus of many stormwater management practices. These practices are referred to as green infrastructure.

  22. Low Impact Development (LID) - Techniques and design considerations that help manage the rainwater that falls on your property by allowing some to evaporate back into the air, some to absorb into the ground, some to be captured and used later as needed, and the rest to slowly pass into the stormwater system and into nearby streams.

  23. Municipal Separate Storm Sewer System (MS4) - A storm system that flows through its own set of pipes rather than being combined with the sanitary sewer system.

  24. National Pollutant Discharge Elimination System (NPDES) - A permit program, created in 1972 by the Clean Water Act (CWA), that helps address water pollution by regulating point sources that discharge pollutants to waters of the United States.

  25. Nonpoint Source Pollution - Pollution that cannot be easily traced to one source or property because small amounts come from many sources and properties. It occurs when rainfall, snowmelt, or irrigation runs over land or through the ground, picks up pollutants, and deposits them into streams, rivers, lakes, and coastal waters or introduces them into groundwater. These numerous small amounts of pollutants eventually accumulate to become harmful amounts.

  26. Point Discharge - The release of collected and/or concentrated surface and stormwater. It is typically the place where collected stormwater leaves a site.

  27. Outfall - A point where collected and concentrated surface and stormwater runoff is discharged from a pipe system or culvert.

  28. 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.

  29. Riprap - A layer of large stones placed to prevent erosion or sloughing of a structure of embankment due to the flow of surface and stormwater runoff. Where riprap is placed on soil, a geotextile fabric should be placed between the stone and the soil to keep the stone from being “swallowed” by the mud.

  30. 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. There are areas that are officially designed by the Army Corps of Engineers as a delineated wetland, and must not be disturbed during land development.

BONUS TERM (because it is funny)

Beaver deceiver - A constructed flow control device that reduces beaver damming activities. It is a non-lethal beaver management technique.

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