Some definitions in this glossary are adapted from definitions in applicable sections of the Connecticut General Statutes and the Regulations of Connecticut State Agencies, as well as related guidance documents such as the Connecticut Guidelines for Soil Erosion and Sediment Control. Refer to these sources for complete definitions.

 

Advanced Treatment – Pollutant removal techniques typically used in drinking water treatment processes but with potential for application as advanced treatment options for stormwater. These treatment techniques include ion exchange, reverse osmosis, disinfection, ultrafiltration, alum injection, and use of water-soluble anionic polyacrylamide (PAM).

 

Agricultural Runoff – Runoff from land utilized for agricultural practices including growing crops and raising livestock.

 

Alternative Site Design – Innovative site design practices have been developed as alternatives to traditional development to control stormwater pollution and protect the ecological integrity of developing watersheds.  Research has demonstrated that alternative site design can reduce impervious cover, runoff volume, pollutant loadings, and development costs when compared to traditional development.

 

Alum Injection – Injection of aluminum phosphate (alum), which has been used extensively as a flocculent in pond and lake management applications, for reducing concentrations of fine sediment and phosphorus in stormwater discharges to eutrophic water bodies.

 

Aquatic Bench – A ten-foot wide bench located around the inside perimeter of a permanent pool that is normally vegetated with aquatic plants to provide pollutant removal.

 

Aquifer – A porous water-bearing formation of permeable rock, sand or gravel capable of yielding economically significant quantities of groundwater.

 

Baseflow – The portion of streamflow that is not due to storm runoff but is the result of groundwater discharge or discharge from lakes or similar permanent impoundments of water.

 

Biochemical Oxygen Demand (BOD) – A measure of the quantity of organic material that can be decomposed through oxidation by micro-organisms.

 

Bioretention – A practice to manage and treat stormwater runoff by using a specially designed planting soil bed and planting materials to filter runoff stored in a shallow depression.  The areas consist of a mix of elements each designed to perform different functions in the removal of pollutants and attenuation of stormwater runoff.

 

Building Setbacks – The distance between a structure and a property boundary (front, rear, or side) of the lot on which the structure is located.

 

Catch Basin Inserts – A structure, such as a tray, basket, or bag that typically contains a pollutant removal medium (i.e., filter media) and a method for suspending the structure in the catch basin. They are placed directly inside of existing catch basins where stormwater flows into the catch basin and is treated as it passes through the structure.

 

Catch Basin – A structure placed below grade to conduct water from a street or other paved surface to the storm sewer.

Check Dams - Small temporary dams constructed across a swale or drainage ditch to reduce the velocity of concentrated stormwater flows.

 

Chemical Oxygen Demand (COD) - A measure of the amount of organic material that can be chemically oxidized.

 

Cisterns – Containers that store larger quantities of rooftop stormwater runoff and may be located above or below ground. Cisterns can also be used on residential, commercial, and industrial sites. Also see Rain Barrel.

 

Coagulant – A chemical added to wastewater or stormwater that destabilizes the surface charge of fine particles, allowing the particles to come together to form larger particles that can be more easily removed by gravity settling and other physical treatment processes. Alum is a common coagulant used in lake management applications and sometimes used for stormwater treatment.

 

Coastal Area - As defined in CGS Section 22a-94(a), land and water within the towns listed in Table 1-2 of this manual.

 

Coastal Boundary - As defined in CGS Section 22a-94(b), a region within the coastal area delineated by the contour elevation of the one hundred year frequency coastal flood zone, as defined and determined by the National Flood Insurance Act, or a one thousand foot linear setback measured from the mean high water mark in coastal waters, or a one thousand foot linear setback measured from the inland boundary of tidal wetlands mapped under section 22a-20, whichever is farthest inland.

 

Combined Sewer Overflows (CSOs) – Combined sewers collect both stormwater runoff and sanitary wastewater in a single set of sewer pipes.  When combined sewers do not have enough capacity to carry all the runoff and wastewater or the receiving water pollution control plant cannot accept all the combined flow, the combined wastewater overflows from the collection system into the nearest body of water, creating a CSO.

 

Darcy’s Law – An equation stating that the rate of fluid flow through a porous medium is proportional to the potential energy gradient within the fluid. The constant of proportionality is the hydraulic conductivity, which is a property of both the porous medium and the fluid moving through the porous medium.

Deep Sump Catch Basins - Storm drain inlets that typically include a grate or curb inlet and a sump to capture trash, debris and some sediment and oil and grease.  Also known as an oil and grease catch basin.

 

Deicers - Materials applied to reduce icing on paved surfaces.  These consist of salts and other formulated materials that lower the melting point of ice, including sodium chloride, calcium chloride, calcium magnesium acetate, and blended products consisting of various combinations of sodium, calcium, magnesium, and chloride, as well as other constituents.

Deicing Constituents – Additives included in deicing materials to prevent caking and inhibit corrosion.

 

Dissolved Pollutants – Non-particulate pollutants typically removed through removal mechanisms such as adsorption, biological uptake, chemical precipitation or ion exchange.

Downstream Analysis - Calculation of peak flows, velocities, and hydraulic effects at critical downstream locations to ensure that proposed projects do not increase post-development peak flows and velocities at these locations.

 

Dry Detention Pond – Stormwater basin designed to capture, temporarily hold, and gradually release a volume of stormwater runoff to attenuate and delay stormwater runoff peaks.  Dry detention ponds provide water quantity control (peak flow control and stream channel protection) as opposed to water quality control.  Also known as “dry ponds” or “detention basins”.

 

Dry Well - Small excavated pits or trenches filled with aggregate that receive clean stormwater runoff primarily from building rooftops.  Dry wells function as infiltration systems to reduce the quantity of runoff from a site. The use of dry wells is applicable for small drainage areas with low sediment or pollutant loadings and where soils are sufficiently permeable to allow reasonable rates of infiltration.

 

Emergency Spillway – Auxiliary outlet to a water impoundment that transmits floodwater exceeding the capacity of the primary spillway.

 

Erosion – The wearing away of land surface by running water, wind, ice or other geological agents, including such processes as gravitational creep.

 

Erosion and Sediment Control – A device placed, constructed on, or applied to the landscape that prevents or curbs the detachment of soil, its movement, and/or deposition.

 

Failing Septic System – An on-site wastewater disposal system that discharges effluent into the ground at concentrations that exceed water quality standards.  Failing systems can be significant sources of nutrients, especially nitrogen, and microbial pathogens to both surface water and groundwater.

 

Filter Strip – A strip or area of vegetation for removing sediment, organic material, nutrients and chemicals from runoff or wastewater.  They are typically located downgradient of stormwater outfalls and level spreaders to reduce flow velocities and promote infiltration/filtration.

 

Filtering Practices - Practices that capture and store stormwater runoff and pass it through a filtering media such as sand, organic material, or soil for pollutant removal.  Stormwater filters are primarily water quality control devices designed to remove particulate pollutants and, to a lesser degree, bacteria and nutrients.

 

Floodplain – Any land susceptible to being inundated by water, usually adjacent to a stream, river or water body and usually associated with a particular design flooding frequency (e.g., 100-year floodplain).

Flow Splitter – An engineered, hydraulic structure designed to divert a percentage of stormwater to a treatment practice located outside of the primary channel or to direct stormwater to a parallel pipe system or to bypass a portion of baseflow around a treatment practice.

 

Fourth Order Stream – Stream order indicates the relative size of a stream based on Strahler’s (1957) method. Streams with no tributaries are first order streams, represented as the start of a solid line on a 1:24,000 USGS Quadrangle Sheet. A second order stream is formed at the confluence of two first order streams, and so on.

 

Fresh-tidal Wetland - a tidal wetland with an annual average salinity of less than 0.5 parts per thousand.

 

Full Sedimentation Design - Stormwater filter system design involving storage and pretreatment of the entire water quality volume.

 

Grass Drainage Channels - Traditional vegetated open channels, typically trapezoidal, triangular, or parabolic in shape, whose primary function is to provide non-erosive conveyance, typically up to the 10-year frequency design flow.  They provide limited pollutant removal through filtration by grass or other vegetation, sedimentation, biological activity in the grass/soil media, as well as limited infiltration if underlying soils are pervious.

 

Groundwater Recharge – The process by which water that seeps into the ground, eventually replenishing groundwater aquifers and surface waters such as lakes, streams, and the oceans.  This process helps maintain water flow in streams and wetlands and preserves water table levels that support drinking water supplies.

 

Groundwater Recharge Volume (GRV) - The post-development design recharge volume (i.e., on a storm event basis) required to minimize the loss of annual pre-development groundwater recharge.  The GRV is determined as a function of annual pre-

development recharge for site-specific soils or surficial materials, average annual rainfall volume, and amount of impervious cover on a site.

 

Heavy Metals - Metals such as copper, zinc, barium, cadmium, lead, and mercury, which are natural constituents of the Earth's crust.  Heavy metals are stable and persistent environmental contaminants since they cannot be degraded or destroyed.

 

Hydraulic Conductivity – The rate at which water moves through a saturated porous media under a unit potential-energy gradient. It is a measure of the ease of water movement in soil and is a function of the fluid as well as the porous media through which the fluid is moving.  The field infiltration rate can be approximated by the saturated hydraulic conductivity.

 

Hydraulic Head – The kinetic or potential energy of a unit weight of water expressed as the vertical height of water above a reference datum.

 

Hydrocarbons – Inorganic compounds consisting of carbon and hydrogen, including petroleum hydrocarbons derived from crude oil, natural gas, and coal.

 

Hydrodynamic Separators – A group of stormwater treatment technologies designed to remove large particle total suspended solids and large oil droplets, consisting primarily of cylindrical-shaped devices that are designed to fit in or adjacent to existing stormwater drainage systems.  The most common mechanism used in these devices is vortex-enhanced sedimentation, where stormwater enters as tangential inlet flow into the side of the cylindrical structure. As the stormwater spirals through the chamber, the swirling motion causes the sediments to settle by gravity, removing them from the stormwater.

 

Hydrograph – A graph showing the variation in discharge or depth of a stream of water over time.

 

Hydrologic Cycle – The distribution and movement of water between the earth’s atmosphere, land, and water bodies.

 

Hydrologic Zones – Planting zones that reflect the degree and duration of inundation by water, consisting of a deep water pool, shallow water bench, shoreline fringe, riparian fringe, floodplain terrace, and upland slopes.

 

Illicit Discharges - Unpermitted discharges to waters of the state that do not consist entirely of stormwater or uncontaminated groundwater except certain discharges identified in the DEP Phase II Stormwater General Permit.

 

Impaired Waters [303(d) List] – Those water bodies not meeting water quality standards. This list of impaired waters within each state is referred to as the “303(d) List” and is prepared pursuant to Section 303(d) of the Federal Clean Water Act.

 

Impervious Surfaces – Surfaces that cannot infiltrate rainfall, including rooftops, pavement, sidewalks, and driveways.

 

Infiltration Practices – Stormwater treatment practices designed to capture stormwater runoff and infiltrate it into the ground over a period of days, including infiltration trenches and infiltration basins.

 

Infiltration Rate – A soil characteristic determining or describing the maximum rate at which water can enter the soil under specific conditions.

 

Instantaneously Mixed Reservoir – A hypothetical model of a natural water body or impoundment in which the contents are sufficiently well-mixed as to be uniformly distributed.

 

Integrated Pest Management (IPM) – An approach to pesticide usage that combines monitoring; pest trapping; establishment of action thresholds; use of resistant varieties and cultivars; cultural, physical, and biological controls; and precise timing and application of pesticide treatments to avoid the use of chemical pesticides when possible and use the least toxic pesticide that targets the pest of concern, when pesticide usage is unavoidable.

 

Low Flow Orifice – Principal outlet of a stormwater treatment practice to convey flows above the permanent pool elevation.

 

Low Impact Development (LID) - Low impact development is a site design strategy intended to maintain or replicate predevelopment hydrology through the use of small-scale controls integrated throughout the site to manage runoff as close to its source as possible.

 

Media Filters – These devices consist of media, such as pleated fabric, activated charcoal, perlite, amended sand and perlite mixes, or zeolite placed within filter cartridges that are typically enclosed in concrete vaults. Stormwater is passed through the media, which traps particulates and/or soluble pollutants

 

Micropool – A smaller permanent pool that is incorporated into the design of a larger stormwater pond to avoid resuspension of particles.

 

Municipal Separate Storm Sewer System (MS4) - conveyances for stormwater, including, but not limited to, roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man‑made channels or storm drains owned or operated by any municipality, sewer or sewage district, fire district, State agency or Federal agency and discharging directly to surface waters of the state.

 

Native Plants - Plants that are adapted to the local soil and rainfall conditions and that require minimal watering, fertilizer, and pesticide application.

 

Nitrate - One of the forms of nitrogen found in aquatic ecosystems. It is produced during nitrification and denitrification by bacteria. Nitrate is the most completely oxidized state of

nitrogen commonly found in water, and is the most readily available state utilized for plant growth.

 

Nitrite - A form of nitrogen that is the end-product of nitrification, which is produced by Nitrobacter spp. Nitrite is also the initial substrate for denitrification.

Nonpoint Source Pollution – Pollution caused by diffuse sources that are not regulated as point sources and are normally associated with precipitation and runoff from the land or percolation.

 

Non-Routine Maintenance - Corrective measures taken to repair or rehabilitate stormwater controls to proper working condition.  Non-routine maintenance is performed as needed, typically in response to problems detected during routine maintenance and inspections.

 

Non-Structural Controls – Pollution control techniques, such as management actions and behavior modification that do not involve the construction or installation of devices.

 

Oil/Particle Separators - Consist of one or more chambers designed to remove trash and debris and to promote sedimentation of coarse materials and separation of free oil (as opposed to emulsified or dissolved oil) from stormwater runoff.  Oil/particle separators are typically designed as off-line systems for pretreatment of runoff from small impervious areas, and therefore provide minimal attenuation of flow. Also called oil/grit separators, water quality inlets, and oil/water separators.

 

Open Space Development - A compact form of development that concentrates density in one portion of the site in exchange for reduced density elsewhere. Also known as cluster or conservation development.

 

Optical Brighteners - Fluorescent white dyes that are additives in laundry soaps and detergents and are commonly found in domestic wastewater.

 

Partial Sedimentation Design - Stormwater filter system design involving storage and pretreatment of a portion of the water quality volume.

 

Peak Flow Control - Criteria intended to address increases in the frequency and magnitude of a range of potential flood conditions resulting from development and include stream channel protection, conveyance protection, peak runoff attenuation, and emergency outlet sizing.

 

Performance Monitoring – Collection of data on the effectiveness of individual stormwater treatment practices.

 

Permanent (Wet) Pool – An area of a detention basin or flood control project that has a fixed water surface elevation due to a manipulation of the outlet structure.

Permeable Paving Materials - Materials that are alternatives to conventional pavement surfaces and are designed to increase infiltration and reduce stormwater runoff and pollutant loads. Alternative materials include modular concrete paving blocks, modular concrete or plastic lattice, cast-in-place concrete grids, and soil enhancement technologies. Stone, gravel, and other low-tech materials can also be used as alternatives for low traffic applications such as driveways, haul roads, and access roads

Phase II Stormwater – The second phase of the NPDES program which specifically targets certain regulated small MS4s and construction activity disturbing between one and five acres of land.

 

Plug Flow – A hypothetical model of a natural water body or impoundment in which advection dominates (i.e., substances are discharged in the same sequence in which they enter).

 

Point Source - any discernible, confined and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, landfill leachate collection system, vessel or other floating craft from which pollutants are or may be discharged.

 

Porous Pavement – Porous pavement is similar to conventional asphalt or concrete but is formulated to have more void space for greater water passage through the material.

 

Pretreatment – Techniques used in stormwater management to provide storage and removal of coarse materials, floatables, or other pollutants before the primary treatment practice.

 

Primary Stormwater Treatment Practice – Stormwater treatment practices that are capable of providing high levels of water quality treatment as stand-alone devices; can be grouped into five major categories – stormwater ponds, stormwater wetlands, infiltration practices, filtering practices, and water quality swales.

 

Principal Spillway – The primary pipe or weir that carries baseflow and storage flow through the embankment.

 

Quality Assurance Project Plan (QAPP) - A document describing the planning, implementation, and assessment procedures for a particular project, as well as any specific quality assurance and quality control activities. It integrates all the technical and quality assurance and control aspects of the project to provide a comprehensive plan for obtaining the type and quality of environmental data and information needed for a specific decision or use.

 

Rain Barrels - Barrels designed to retain small volumes of runoff for reuse for gardening and landscaping.  They are applicable to residential, commercial, and industrial sites and can be incorporated into a site’s landscaping plan.  The size of the rain barrel is a function of rooftop surface area and the design storm to be stored.

 

Rain Garden - Functional landscape elements that combine plantings in depressions that allow water to pool for only a few days after a rainfall then be slowly absorbed by the soil and plantings.

 

Rainwater Harvesting –The collection and conveyance of rainwater from roofs and storage in either rain barrels or cisterns.  Depending on the type and reuse of the rainwater, purification may be required prior to distribution of the rainwater for reuse. Harvested rainwater can be used to supply water for drinking, washing, irrigation, and landscaping.

 

Rational Equation – An equation that may be appropriate for estimating peak flows for small urbanized drainage areas with short times of concentration, but does not estimate runoff volume and is based on many restrictive assumptions regarding the intensity, duration, and aerial coverage of precipitation.

 

Retention (or Residence) Time - The average length of time that a “parcel” of water spends in a stormwater pond or other water body.

 

Riser – A vertical pipe extending from the bottom of a pond that is used to control the discharge rate for a specified design storm.

Routine Maintenance - Maintenance performed on a regular basis to maintain proper operation and aesthetics.

 

Runoff Capture Volume (RCV) - The runoff capture volume is equivalent to the water quality volume (WQV) and is the stormwater runoff volume generated by the first inch of rainfall on the site.

 

Safety Bench – A flat area above the permanent pool and surrounding a stormwater pond or wetland to provide separation from the pool and adjacent slopes.

 

Seasonally High Groundwater Table – The highest elevation of the groundwater table typically observed during the year.

 

Secondary Stormwater Treatment Practices - Stormwater treatment practices that may not be suitable as stand-alone treatment because they either are not capable of meeting the water quality treatment performance criteria or have not yet received the thorough evaluation needed to demonstrate the capabilities for meeting the performance criteria.

 

Sediment Chamber or Forebay – A underground chamber or surface impoundment (i.e., forebay) designed to remove sediment and/or floatables prior to a primary or other secondary stormwater treatment practice.

 

Sensitive Watercourse – Streams, brooks, and rivers that are classified by DEP as Class A (fishable, swimmable, and potential drinking water), as well as their tributary watercourses and wetlands, that are high quality resources that warrant a high degree of protection.

Shallow Marsh – The portion of a stormwater wetland that consists of aquatic vegetation within a permanent pool ranging in depth from 6” to 18” during normal conditions.

 

Shared Parking – A strategy that reduces the number of parking spaces needed by allowing adjacent land uses with different peak parking demands to share parking lots.

 

Site Planning and Design – Techniques of engineering and landscape design that maintaining predevelopment hydrologic functions and pollutant removal mechanisms to the extent practical.

 

Site Stormwater Management Plan - Plan describing the potential water quality and quantity impacts associated with a development project both during and after construction. It also identifies selected source controls and treatment practices to address those potential impacts, the engineering design of the treatment practices, and maintenance requirements for proper performance of the selected practices.

 

Soil Infiltration Capacity – The maximum rate at which water can infiltrate into the soil from the surface.

 

Soluble Phosphorus - Soluble phosphorus is present predominantly as the ionic species orthophosphate and is thought to be the form readily taken up by plants, i.e., "bioavailable.”

 

Source Controls - Practices to limit the generation of stormwater pollutants at their source.

 

Stormwater – Water consisting of precipitation runoff or snowmelt.

 

Stormwater Hotspots - Land uses or activities with potential for higher pollutant loads.

 

Stormwater Pollution Prevention Plan (SWPPP) - Identifies potential sources of pollution and outlines specific management activities designed to minimize the introduction of pollutants into stormwater.

 

Stormwater Ponds –Vegetated ponds that retain a permanent pool of water and are constructed to provide both treatment and attenuation of stormwater flows.

 

Stormwater Retrofits – Modifications to existing development to incorporate source controls and structural stormwater treatment practices to remedy problems associated with and improve water quality mitigation functions of older, poorly designed, or poorly maintained stormwater management systems.

Stormwater Treatment Practices – Devices constructed for primary treatment, pretreatment or supplemental treatment of stormwater.

 

Stormwater Treatment Train - Stormwater treatment practices, as well as site planning techniques and source controls, combined in series to enhance pollutant removal or achieve multiple stormwater objectives.

 

Stormwater Wetlands – Shallow, constructed pools that capture stormwater and allow for the growth of characteristic wetland vegetation.

 

Street Sweepers – Equipment to remove particulate debris from roadways and parking lots, including mechanical broom sweepers, vacuum sweepers, regenerative air sweepers and dry vacuum sweepers.

 

Structural Controls – Devices constructed for temporary storage and treatment of stormwater runoff.

 

Submerged Aquatic Vegetation (SAV) – Includes rooted, vascular, flowering plants that live permanently submerged below the water in coastal, tidal and navigable waters.

 

Synthetic Organic Chemicals – Chemicals that contain carbon, but are not naturally occurring.

 

Technology Acceptance and Reciprocity Partnership (TARP) – TARP was formed by the states of California, Illinois, Maryland, Massachusetts, New Jersey, New York, Pennsylvania, and Virginia to development standard protocols for the collection and evaluation of performance data for new environmental technologies.

 

Tidal Wetland – As defined in CGS Section 22a-29(2), those areas that border on or lie beneath tidal waters whose surface is at or below an elevation of one foot above local extreme high water and upon which may grow or be capable of growing some, but not necessarily all, of a list of specific plant species.

 

Time of Concentration –The time required for water to flow from the most distant point to the downstream outlet of a site.  Runoff flow paths, ground surface slope and roughness, and channel characteristics affect the time of concentration.

 

Total Kjeldahl Nitrogen (TKN) – The sum of the ammonia nitrogen and the organic bounded nitrogen; nitrates and nitrites are not included.

 

Total Maximum Daily Load (TMDL) - A calculation of the maximum amount of a pollutant that a water body can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources, including a margin of safety.

 

Total Nitrogen – The sum of total Kjeldahl nitrogen, nitrate, and nitrite.  Nitrogen is typically the growth-limiting nutrient is estuarine and marine systems.

 

Total Organic Carbon – A measure of the organic matter content. The amount of organic matter content affects biogeochemical processes, nutrient cycling, biological availability, chemical transport and interactions and also has direct implications in the planning of wastewater treatment and drinking water treatment.

 

Total Phosphorus – Sum of orthophosphate, metaphosphate (or polyphosphate) and organically bound phosphate. Phosphorus is typically the growth-limiting nutrient is freshwater systems.

 

Total Suspended Solids – The total amount of particulate matter that is suspended in the water column.

 

Technical Release Number 55 (TR-55) – A watershed hydrology model developed by the Soil Conservation Service (now Natural Resource Conservation Service) used to calculate runoff volumes, peak flows, and simplified routing for storm events through ponds.

 

Trash Rack – A structural device (e.g., screen or grate) used to prevent debris from entering a spillway, channel, drain, pump or other hydraulic structure.

 

Underground Detention Facilities - Vaults, pipes, tanks, and other subsurface structures designed to temporarily store stormwater runoff for water quantity control and to drain completely between runoff events.  They are intended to control peak flows, limit downstream flooding, and provide some channel protection.

 

Underground Infiltration Systems – Structures designed to capture, temporarily store, and infiltrate the water quality volume over several days, including premanufactured pipes, vaults, and modular structures. Used as alternatives to infiltration trenches and basins for space-limited sites and stormwater retrofit applications.

 

Urban Stormwater Runoff - Stormwater runoff from developed areas.

 

Vegetated Buffer - An area or strip of land in permanent undisturbed vegetation adjacent to a water body or other resource that is designed to protect resources from adjacent development during construction and after development by filtering pollutants in runoff, protecting water quality and temperature, providing wildlife habitat, screening structures and enhancing aesthetics, and providing access for recreation.

 

Vegetated Filter Strips and Level Spreaders - Uniformly graded vegetated surfaces (i.e., grass or close-growing native vegetation) located between pollutant source areas and downstream receiving waters or wetlands. A level spreader is usually located at the top of slope to distribute overland flow or concentrated runoff (see the maximum overland flow length guidelines above) evenly across the entire length of the filter strip.

 

Vegetated Roof Covers - Multilayered, constructed roof systems consisting of a vegetative layer, media, a geotextile layer, and a synthetic drain layer installed on building rooftops. Rainwater is either intercepted by vegetation and evaporated to the atmosphere or retained in the substrate before being returned to the atmosphere through transpiration and evaporation. Also referred to as green roofs.

 

Water Balance – Equation describing the input, output, and storage of water in a watershed or other hydrologic system.

 

Water Quality Flow (WQF) – The peak flow associated with the water quality volume calculated using the NRCS Graphical Peak Discharge Method.

 

Water Quality Swales - Vegetated open channels designed to treat and attenuate the water quality volume and convey excess stormwater runoff.   Dry swales are primarily designed to receive drainage from small impervious areas and rural roads. Wet swales are primarily used for highway runoff, small parking lots, rooftops, and pervious areas.

 

Water Quality Volume (WQV) – The volume of runoff generated by one inch of rainfall on a site.

 

Watershed Management - Integrated approach addressing all aspects of water quality and related natural resource management, including pollution prevention and source control.

 

Xeriscaping - Landscaping to minimize water usage (“xeri” is the Greek prefix meaning ”dry”) by using plants that are adapted to the local climate and require minimal watering, fertilizer, and pesticide application, and improving soils by adding soil amendments or using mulches to reduce the need for watering by increasing the moisture retained in the soil.