Glossary of Terms

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

Average Particle Size

Average size of suspended solids expected to be exported from the site by stormwater runoff.

Aquifer

A geologic stratum containing groundwater that can be withdrawn and used for human purposes.

Backwater

Water upstream from an obstruction which is deeper than it would normally be without the obstruction.

Baffle

A device to deflect, check or regulate flow.

Basin

Any area draining to a point of interest. Basins of interest to King County staff are those that drain either to the Cedar, Green, Snoqualmie, Skykomish, or White rivers, or the drainage areas which drain directly to Puget Sound.

Basin plan

A plan and all implementing regulations and procedures including but not limited to capital projects, public education activities, land use management regulations adopted by ordinance for managing surface and storm water management facilities, and features within individual subbasins.

Berm

A constructed barrier of compacted earth.

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.

Best Management Practices (BMPs)

BMPs are Best Management Practices used to control the generation and delivery of pollutants from the built environment to water ways, thereby reducing the amount of pollutants entering surface and ground waters. BMPs can be structural like a Vortechs System or can be non-structural, like street sweeping.

Buffer

A designated area adjacent to and a part of a steep slope or landslide hazard area which protects slope stability, attenuation of surface water flows, and landslide hazards reasonably necessary to minimize risk; or a designated area adjacent to or a part of a stream or wetland that is an integral part of the stream or wetland ecosystem.

Catch basin

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

Catch basin insert

A device installed underneath a catch basin inlet to treat stormwater through filtration, settling, absorption, adsorption, or a combination of these mechanisms. There are a number of shapes, sizes, and configurations of inserts available.

Channel

A long, narrow excavation or surface feature that conveys surface water and is open to the air.

Channel, constructed

A channel or ditch constructed to convey surface water; also includes reconstructed natural channels.

Channel, natural

A channel which has occurred naturally due to the flow of surface waters; or a channel that, although originally constructed by human activity, has taken on the appearance of a natural channel including a stable route and biological community. Clean Water Act (Water Quality Act): (formerly the Federal Water Pollution Control Act or Federal Water Pollution Control Act Amendments of 1972). Public law 92-500; 33 U.S.C. 1251 et seq.; legislation which provides statutory authority for the NPDES program. Also know as the Federal Water Pollution Control Act.

Closed depression

An area which is low-lying and either has no surface water outlet, or has such a limited outlet that during storm events the area acts as a retention basin, with more than 5000 square feet of water surface area at overflow elevation.

CSO

Combined Sewer Overflow

Constructed conveyance system facilities

Gutters, ditches, pipes, channels, and most flow control and water quality treatment facilities.

Conveyance

The process of water moving from one place to another.

Critical Drainage Area

An area with such severe flooding, drainage, and/or erosion/sedimentation conditions which have resulted or will result from the cumulative impacts of development and urbanization, that the area has been formally adopted as a Critical Drainage Area by rule under the procedures specified in KCC 2.98.

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.

Dead storage

The volume available in a depression in the ground below any conveyance system, or surface drainage pathway, or outlet invert elevation that could allow the discharge of surface and storm water runoff.

Debris Barrier

A metal trash rack

DNRP

Department of Natural Resources and Parks

Depression storage

The amount of precipitation that is trapped in depressions on the surface of the ground.

Detention facility

A facility that collects water from developed areas and releases it at a slower rate than it enters the collection system. The excess of inflow over outflow is temporarily stored in a pond or a vault and is typically released over a few hours or a few days.

Detention Vault

A type of detention facility.

Direct discharge

Undetained discharge from a proposed project to a major receiving water.

Discharge

The volume of water (and suspended sediment if surface water) that passes a given location within a given period of time.

Diversion

A change in the natural discharge location or runoff flows onto or away from an adjacent downstream property.

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.  An Area of catchment contributing runoff to the treatment system.

Drainage facility

A constructed or engineered feature that collects, conveys, stores or treats surface and storm water runoff. Drainage facilities shall include but not be limited to all constructed or engineered streams, pipelines, channels, ditches, gutters, lakes, wetlands, closed depressions, flow control or water quality treatment facilities, erosion and sedimentation control facilities, and other drainage structures and appurtenances that provide for drainage.

EIS

Environmental Impact Statement. A document that discusses the likely significant adverse impacts of a proposal, ways to lessen the impacts, and alternatives to the proposal. It is required by the national and state environmental policy acts when projects are determined to have the potential for significant environmental impact.

Embankment

A structure of earth, gravel, or similar material raised to form a pond bank or foundation for a road.

EPA

Environmental Protection Agency

ESA

Endangered Species Act

Energy Dissipater

A rock pad constructed at inlets/outlets to prevent erosion, or a constructed percolation trench to disperse outletting flows over a large area, or a catch basin used to slow fast flowing runoff. Catch basins may be a part of the dispersion trench.

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.

ESC

Erosion and Sediment Control

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.

Excavation

The process of removing earth, stone, or other materials from land.

FEMA

Federal Emergency Management Agency

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.

Flood Control Channel

The open portion (often concrete-lined) of the storm drain system

Flow control facility

A drainage facility designed to mitigate the impacts of increased surface and storm water runoff generated by site development pursuant to the drainage requirements. Flow control facilities are designed either to hold water for a considerable length of time and then release it by evaporation, plant transpiration, and/or infiltration into the ground, or to hold runoff a short period of time and then release it to the conveyance system.

Flow control standards

The level of flow control required is based on the resource value of the receiving system in terms of its hydrology, ecology, geology and water quality.

FROP

Flow Restrictor/Oil Pollution control device.

General Permit

A permit issued under the NPDES program to cover a certain class or category of stormwater discharges. These permits reduce the administrative burden of permitting stormwater discharges.

Grading

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

Groundwater

Underground water usually found in aquifers. Groundwater usually originates from infiltration. Wells tap the groundwater for water supply uses.

Gutter

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

Habitat

The specific area or environment in which a particular type of plant or animal lives and grows.

Hardpan

A cemented or compacted and often clay-like layer of soil that is impenetrable by roots.

Harmful pollutant

A substance that has adverse effects to an organism including death, chronic poisoning, impaired reproduction, cancer, or other effects.

HRT

Hydraulic residence time

Hydrologic cycle

The circuit of water movement from the atmosphere to the earth and return to the atmosphere through various stages or processes such as precipitation, interception, runoff, infiltration, percolation, storage, evaporation, and transpiration.

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

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 of non-stormwater to the storm drainage system. Examples are discharges from internal 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.

Impervious surface

A hard surface area which either prevents or retards the entry of water into the soil mantle as under natural conditions prior to development; and/or a hard surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development.

Common impervious surfaces include, but are not limited to, roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam, or other surfaces which similarly impede the natural infiltration of surface and storm water runoff. Open, uncovered flow control or water quality treatment facilities shall not be considered impervious surfaces for determinations of thresholds. For the purpose of modeling though, onsite flow control and water quality ponds are modeled as impervious surface per Chapter 3 of the King County Surface Water Design Manual.

Impoundment

A natural or man-made containment for surface water.

Industrial Activity

Any activity which is directly related to manufacturing, processing or raw materials storage areas at an industrial plant.

Infiltration/Inflow (I/I)

Clean storm and/or groundwater that enters the sewer system through cracked pipes, leaky manholes, or improperly connected storm drains, down spouts and sump pumps. Most inflow comes from stormwater and most infiltration comes from groundwater. I/I affects the size of conveyance and treatment systems and, ultimately, the rate businesses and residents pay to operate and maintain them

Invert

Elevation to the inside bottom of the pipe.

Lake

An area permanently inundated by water in excess of two meters (7 ft) deep and greater than twenty acres in size as measured at the ordinary high water mark.

Large Municipal Separate Storm Sewer System (MS4)

An MS4 located in an incorporated place or county with a population of 250,000 or more, as determined by the latest U.S. Census.

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.

Medium Municipal Separate Storm Sewer System (MS4)

MS4 located in an incorporated place or county with a population of 100,000 or more but less than 250,000, as determined by the latest U.S. Census.

Municipal Separate Storm Sewer System (MS4)

A publically-owned conveyance or system of conveyances that discharges to waters of the U.S. and is designed or used for collecting or conveying stormwater, is not a combined sewer, and is not part of a publicly-owned treatment works (POTW).

Small MS4s

A small MS4 is defined as any MS4 that is not a medium or large MS4 covered by Phase I of the NPDES Storm Water Program.

Medium MS4s

A medium MS4 is a system that is located in an area with a population between 100,000 - 249,999

Large MS4s

A large MS4 is a system that is located in an area with a population of 250,000 or more. King County is a large MS4. So are the Cities of Tacoma and Seattle.

Other MS4s

Other MS4s can be any size. These systems were designated by NPDES permitting authorities due to interrelationships with other MS4s. The Washington State Department of Transportation is an Other MS4.

Multi-Sector General Permit (MSGP)

An NPDES permit that regulates stormwater discharges from eleven categories of industrial activities.

Natural conveyance system elements

Swales and small drainage courses, streams, rivers, lakes, and wetlands.

Natural onsite drainage feature

A natural swale, channel, stream, closed depression, wetland, or lake.

Net Annual TSS Load Reduction

Suspended solids removal efficiency target.

Non-authorized States

Any State that does not have the authority to regulate the NPDES Stormwater Program.

Nonpoint source (NPS) pollution

NPS pollution occurs when rainfall, snowmelt, or irrigation runs over land or through the ground, picks up pollutants, and deposits them into rivers, lakes, and coastal waters or introduces them into ground water.

Non-point Source (NPS) Pollutants

Pollutants from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water.

Nonpoint source pollution

Is simply the broad term referring to the type of pollution that is caused by non-specific sources, including human-made and natural pollutants. By contrast, the direct dumping of chemicals into a water body by a factory would be a specific source for pollution.

Nonstructural BMP

A preventative action to protect receiving water quality that does not require construction. Nonstructural BMPs rely predominantly on behavioral changes in order to be effective. Major categories of non-structural BMPs include education, recycling, maintenance practices and source controls.

NPDES

National Pollutant Discharge Elimination System. The part of the Clean Water Act which requires point source discharges to obtain permits. These permits, referred to as NPDES permits, are administered by the Washington State Department of Ecology.

Notice of Intent (NOI)

An application to notify the permitting authority of a facility's intention to be covered by a general permit; exempts a facility from having to submit an individual or group application.

NPDES: "National Pollutant Discharge Elimination System"

The name of the surface water quality program authorized by Congress as part of the 1987 Clean Water Act. This is EPA's program to control the discharge of pollutants to waters of the United States (see 40 CFR 122.2).

Oil/water separator

A vault, usually underground designed to provide a quiescent environment to separate oil from water. Floatables (e.g., styrofoam) are also removed.

Outfall

The point where runoff discharges from a sewer pipe, ditch, or other conveyance to a receiving body of water.

Peak Flow Rate

The peak flow rate associated with an infrequent (typically 5 to 25 year) storm event. 

Percent Impervious

The specific portion of the contributing drainage area that does not allow stormwater to infiltrate, usually expressed as a percent 0-100%.  Examples include asphalt or bituminous surface and other non-porous or compacted surfaces.

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).

Permitting Authority (PA)

The NPDES-authorized state agency or EPA regional office that administers the NPDES Stormwater Program. PAs issue permits, provide compliance assistance, and inspect and enforce the program.

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.

Physically interconnected MS4

This means that one MS4 is connected to a second MS4 in such a way that it allows for direct discharges into the second system.

Point discharge

The release of collected and/or concentrated surface and storm water runoff from a pipe, culvert, or channel.

Point source pollutant

Storm water discharges are generated by runoff from land and impervious areas such as paved streets, parking lots, and building rooftops during rainfall and snow events that often contain pollutants in quantities that could adversely affect water quality. Most storm water discharges are considered point sources and require coverage by an NPDES permit. The primary method to control storm water discharges is through the use of best management practices.

Pollution-generating pervious surface

A non-impervious surface with vegetative ground cover subject to use of pesticides and fertilizers. Such surfaces include, but are not limited to, the lawn and landscaped areas of residential or commercial sites, golf courses, parks, and sports fields.

Pollutant Loading

      The total quantity of pollutants in stormwater runoff.

Qualifying local program

A local, State or Tribal municipal stormwater management program that imposes, at a minimum, the relevant requirements of one or more of the minimum control measures includes in 122.34(b).

Reach

A length of channel with uniform characteristics.

Receiving waters

Bodies of water or surface water systems receiving water from upstream man-made or natural systems.

Recharge

The flow to groundwater from the infiltration of surface and stormwater runoff.

Regulated MS4

Any MS4 covered by the NPDES Stormwater Program (regulated, small, medium, or large MS4s).

Resource stream

A stream section mapped and rated by King County as being a regionally significant stream reach that harbors significant concentrations of fish for some period in their life cycle.

Retention

The process of collecting and holding surface and storm water runoff with no surface outflow.

R/D Facility

Retention and detention facility. A type of drainage facility designed either to hold water for a considerable length of time and then release it by evaporation, plant transpiration, and/or infiltration into the ground, or to hold surface and storm water runoff for a short period of time and then release it to the surface and storm water conveyance system. Also called flow control facilities

Required Efficiency

Suspended solids removal efficiency target.

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.

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.

Desired Treatment Quality

The percent TSS reduction expressed on a net annual or runoff event basis.

Required Swirl Chamber Area

The grit chamber area required to produce a design ratio that will produce a removal efficiency estimate meeting the performance goal. This measurement can be used to determine the size of the smallest system that will meet the performance goal.

Retrofit

The modification of an existing development with or without an existing stormwater management system through the construction and/or enhancement of a manufactured (i.e. a Vortechs System) or natural BMP (best management practice) designed to improve water quality.

Rim    

Elevation at the finish grade.

Runoff

Drainage or flood discharge that leaves an area as surface flow or as pipeline flow. Has reached a channel or pipeline by either surface or sub-surface routes.

Runoff Coefficient

The percentage of rainfall volume that will become runoff.

Sediment

Soil, sand, and minerals washed from land into water, usually after rain. Sediment can destroy fish-nesting areas, clog animal habitats, and cloud waters so that sunlight does not reach aquatic plants.

Sheet flow

The portion of precipitation that moves initially as overland flow in very shallow depths before eventually reaching a stream channel.

Site Plan

A graphical representation of a layout of buildings and facilities on a parcel of land.

Site Runoff

Any drainage or flood discharge that is released from a specified area.

Small Municipal Separate Storm Sewer System (MS4)

Any MS4 that is not regulated under Phase I of the NPDES Stormwater Program and Federally-owned MS4s.

Source control

Action to prevent pollution where it originates.

State Revolving Fund (SRF)

A State-managed revolving fund providing loans for specific water pollution control purposes. Under the SRF program, States and municipalities are primarily responsible for financing, constructing, and managing wastewater treatment facilities. The SRF program is based on the 1987 Amendments to the CWA which replaced the Construction Grants program with the SRF program.

Storm drain system

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

Storm Sewer

A sewer carrying only runoff from storm events.

Storm Water

Runoff water resulting from precipitation.

Stormwater Facility

Facilities that control the discharge of stormwater and that remove pollutants make up the bulk of the structural solutions applied to surface water problems in King County. Stormwater facilities included storage facilities (ponds, vaults, underground tanks, and infiltration systems); water quality facilities (wetponds, biofiltration swales, constructed wetlands, sand filters, and oil/water separators); and conveyance systems (ditches, pipes, and catchbasins).

These systems are most often built in conjunction with new development, but include regional facilities designed and constructed by the Department of Natural Resources.

Once constructed, stormwater facilities require on-going maintenance to ensure they continue to perform as intended. Maintenance of storage facilities typically includes the removal of accumulated sediment and debris, routine mowing, and minor repairs to mechanical appurtenances. Management of water quality facilities is more complex, requiring intensive vegetation management, inspection and maintenance of flow control features, and restoration or replacement of filter media. King County plays an active role in the management of three categories of stormwater facilities: residential, commercial, and regional. These three terms are defined in the following paragraphs.

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

Stormwater Pollution Prevention Plan (SWPPP)

A plan to describe a process whereby a facility thoroughly evaluates potential pollutant sources at a site and selects and implements appropriate measures designed to prevent or control the discharge of pollutants in stormwater runoff.

Structural BMP

Constructed facilities or measures to help protect receiving water quality and control stormwater quantity. Examples include storage, vegetation, infiltration, and filtration.

Surface Water Design Manual

The manual (and supporting documents as appropriate) describing surface and storm water design and analysis requirements, procedures, and guidance

Surface Water

Water that remains on the surface of the ground, including rivers, lakes, reservoirs, streams, wetlands, impoundments, seas, estuaries, etc.

Swale

A shallow drainage conveyance with relatively gentle side slopes, generally with flow depths less than one foot.

Tightline

Typically a continuous length of pipe used to convey flows down a steep or sensitive slope with appropriate energy dissipation at the discharge end.

Time of Concentration

The amount of time it takes a drop of water falling in the hydraulically most distant point in the watershed to reach the Vortechs System.

Total Maximum Daily Load (TMDL)

The maximum amount of pollutants which can released into a water body without adversely affecting the water quality.

Tool Box

A term to describe the activities and materials that EPA plans toperform/produce to facilitate implementation of the stormwater program in an effectiveand cost-efficient manner. The eight components include: 1)fact sheets; 2) guidancedocuments; 3) menu of BMPs; 4) compliance assistance; 5) information clearing house;6) training and outreach efforts; 7) technical research; and 8) support for demonstration projects.

Toxic

Poisonous, carcinogenic, or otherwise directly harmful to life.

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.

Urban Runoff

Stormwater from urban areas, which tends to contain heavy concentrations of pollutants from urban activities.

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.

Water Quality Standards

State-adopted and EPA-approved ambient standards for waterbodies. The standards cover the use of the waterbody and the water quality criteria that must be met to protect the designated use or uses.

Water quality treatment facility

A drainage facility designed to reduce pollutants once they are already contained in surface and storm water runoff. Water quality treatment facilities are the structural component of best management practices (BMPs); when used singly or in combination, WQ facilities reduce the potential for contamination of surface and/or ground waters.

Watershed

A geographic area in which water, sediments, and dissolved materials drain to a common outlet, typically a point on a larger stream, a lake, an underlying aquifer, an estuary, or an ocean. A watershed is also sometimes referred to as the "drainage basin" of the receiving waterbody.

Water Quality Design Flow

The flow which is required or desired to be treated by the structural BMP device.  Often times the design flow is associated with a rainfall depth of intensity that has a high probability of occurrence or frequency (e.g., 50-90% of all rainfall events in a given year occur at an intensity of 0.2 in/hr).

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.

Wetpond

Drainage facilities for water quality treatment that contain a permanent pool of water. They are designed to optimize water quality by providing long retention times (on the order of a week or more) to settle out particles of fine sediment to which pollutants such as heavy metals adsorb, and to allow biologic activity to occur that metabolizes nutrients and organic pollutants. For wetvaults, the permanent pool of water is covered by a lid which blocks sunlight from entering the facility, limiting light-dependent biologic activity.

Wetvault

Drainage facilities for water quality treatment that contain a permanent pool of water. They are designed to optimize water quality by providing long retention times (on the order of a week or more) to settle out particles of fine sediment to which pollutants such as heavy metals adsorb, and to allow biologic activity to occur that metabolizes nutrients and organic pollutants. For wetvaults, the permanent pool of water is covered by a lid which blocks sunlight from entering the facility, limiting light-dependent biologic activity.

Wet Weather Flows

Water entering storm drains during rainstorms/wet weather events.

Abbreviations

BAT    Best Available Technology Economically Achievable
           (applies to non-conventional and toxic pollutants)

BCT    Best Conventional Pollutant Control Technology
           (applies to Conventional pollutants)

BMP    Best Management Practice

BPJ     Best Professional Judgment

BPT     Best Practicable Control Technology Currently Available
            (generally applies to conventional pollutants and some metals)

CFR     Code of Federal Regulations

CGP    Construction General Permit

COD    Chemical Oxygen Demand

CSO    Combined Sewer Overflow

CWA    Clean Water Act
             (formerly referred to as the Federal Water Pollution Control Act or 
              Federal Water Pollution Control Act Amendments of 1972)

CZARA    Coastal Zone Act Reauthorization Amendments

D.O.    Dissolved Oxygen

DMR    Discharge Monitoring Report

ELG    Effluent Limitations Guidelines

EPA    Environmental Protection Agency

FR    Federal Register

MEP    Maximum Extent Practicable

MS4    Municipal Separate Storm Sewer System

MSGP    Multi Sector General Permit

NOI    Notice of Intent

NOT    Notice of Termination

NOV    Notice of Violation

NPDES    National Pollutant Discharge Elimination System

NPS    Non-point Source

O&M    Operation and Maintenance

OW    Office of Water

OWM    Office of Wastewater Management

PA    Permitting Authority

POTW    Publicly Owned Treatment Works

SIC    Standard Industrial Classification

SWPPP    Storm Water Pollution Prevention Plan

TMDL    Total Maximum Daily Load

TSS    Total Suspended Solids

UA    Urbanized Area