The first general permitting option available to regulated industrial facilities and large construction activities. EPA issued the construction baseline general permit on 9/9/92 (57 FR 41176) and the industrial baseline general permit on 9/25/92 (57 FR 44412). The construction baseline general permit has been replaced by the Construction General Permit, issued on 2/17/98 (63 FR 7857). The industrial baseline general permit has largely been replaced by the Multi-Sector General Permit, issued on 9/25/95 (60 FR 50804).

A level of technology based on the very best (state-of-the-art) control and treatment measures that have been developed or are capable of being developed and that are economically achievable within the appropriate industrial category

Activities or structural improvements that help reduce the quantity and improve the quality of stormwater runoff. BMPs include treatment requirements, operating procedures, and practices to control site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage.

Dense vegetation designed to filter stormwater runoff as it passes through

Specific facilities classified as light industry with equipment or materials exposed to stormwater

Code of Federal Regulations

Legislation that provides statutory authority for the NPDES program; Public law 92-500; 33 U.S.C. 1251 et seq. Also known as the Federal Water Pollution Control Act.

The Coastal Nonpoint Source Pollution Control Program (Section 6217) addresses nonpoint pollution problems in coastal waters. Section 6217 requires the 29 states and territories with approved Coastal Zone Management Programs to develop Coastal Nonpoint Pollution Control Programs. In its program, a state or territory describes how it will implement nonpoint source pollution controls, known as management measures, that conform with those described in Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters (available at http://www.epa.gov/owow/nps/MMGI/). This program is administered jointly with the National Oceanic and Atmospheric Administration (NOAA).

The compilation of federal regulations. Each area of regulation is contained in a separate volume (e.g., environmental regulations are compiled in volume 40, or 40 CFR). Each volume contains up to several hundred parts.

The process of water moving from one place to another

Combined sewer overflow

A short, closed (covered) conduit that passes stormwater runoff under an embankment, usually a roadway. A rectangular or square concrete culvert is referred to as a box culvert.

A stormwater system that delays the downstream progress of stormwater runoff in a controlled manner, typically by using temporary storage areas and a metered outlet device

Removal of soil particles by wind and water. Often the eroded debris (silt or sediment) becomes a pollutant via stormwater runoff. Erosion occurs naturally but can be intensified by human activities such as farming, development, road-building, and timber harvesting.

A temporary rise in flow or stage of any watercourse or stormwater conveyance system that results in stormwater runoff exceeding its normal flow boundaries and inundating adjacent, normally dry areas

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.

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)

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

An MS4 located in an incorporated place or county with a population of 250,000 or more, as determined by the 1990 U.S. Census

Described under Category (XI) of the definition of "stormwater discharges associated with industrial activity" [40 CFR 122.26(b)(14)(XI)]. Under the Phase I NPDES program, these facilities were eligible for exemption from stormwater permitting requirements if certain areas and activities were not exposed to stormwater. As a result of the Phase II Final Rule, these facilities must now certify to a condition of no exposure.

A standard for water quality that applies to all MS4 operators regulated under the NPDES 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.

A filter containing sand, compost, sand peat, or perlite and zeolite designed to filter constituents (particulates, oil, bacteria, or dissolved metals) out of stormwater runoff as it passes through the filter

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 1990 U.S. Census

Maximum extent practicable

A publicly owned conveyance or system of conveyances that discharges to waters of the US 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)

Protection of all industrial materials or activities by a storm-resistant shelter to prevent exposure to rain, snow, snowmelt, and/or runoff.

Pollutants from many diffuse sources. Nonpoint-source 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 underground sources of drinking water.

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

National Pollutant Discharge Elimination System, the two-phased surface water quality program authorized by Congress as part of the 1987 Clean Water Act

The NPDES-authorized state agency or EPA regional office that administers the NPDES program, issuing permits, providing compliance assistance, conducting inspections, and enforcing the program

One MS4 connected to a second MS4 in such a way that allows direct discharges into the second system

Pollutants from a single, identifiable source such as a factory or refinery; also called single-point-source pollution

The modification of stormwater management systems through the construction and/or enhancement of wet ponds, wetland plantings, or other BMPs designed to improve water quality

Drainage or flood discharge that leaves an area as surface flow or as pipeline flow

A grant, under section 319 of the Clean Water Act, that pays up to 60% of the cost of a project to prevent or control nonpoint source pollution

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.

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

Low-interest loan to pay for infrastructure investments such as wastewater treatment facilities, landfill closures, and habitat restoration. Federal and state funding provide the seed money, and repayment of earlier loans keeps the system going.

Precipitation that accumulates in natural and/or constructed storage and stormwater systems during and immediately following a storm event

Functions associated with planning, designing, constructing, maintaining, financing, and regulating the facilities (both constructed and natural) that collect, store, control, and/or convey stormwater

A plan to describe a process though which 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

Special assessment district set up to generate a stable source of funding for stormwater management within a region, usually through user fees

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

Stormwater management plan (or program)

The maximum allowable loading of a pollutant that a designated water body can assimilate and still meet numeric and narrative water quality standards. TMDLs were established by the 1972 Clean Water Act. Section 303(d) of the US Water Quality Act requires states to identify water bodies that do not meet federal water quality standards. In 1996 the states developed (with EPA approval) a list of water bodies that failed to meet section 303(d) standards. These are the focus of TMDLs. Allocation of named pollutants is on percentage basis.

A term to describe the activities and materials that EPA plans to perform/produce to facilitate implementation of the stormwater program in an effective and cost-efficient manner. The eight components include fact sheets, guidance documents, menu of BMPs, compliance assistance, information clearinghouse, training and outreach efforts, technical research, and support for demonstration projects.

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/mi.²

Geographical area that drains to a specified point on a water course, usually a confluence of streams or rivers. Also known as drainage area, catchment, or river basin. (In the UK the term "watershed" refers to what in the US is called the drainage divide, and the term "catchment" refers to what in the US is called a watershed.)