NPDES MSGP Permit Glossary: Key Terms & Definitions for Developers and Consultants

NPDES MSGP Permit Key Terms & Definitions

Annual Report: A report that NPDES MSGP permittees must submit to the permitting authority by January 30th of each year, summarizing their monitoring results, inspection findings, corrective actions, and other permit-related activities for the previous calendar year.

Best Management Practices (BMPs): Schedules of activities, prohibitions of practices, maintenance procedures, and other management practices to prevent or reduce the pollution of waters of the United States. BMPs also include treatment requirements, operating procedures, and practices to control plant site runoff, spillage or leaks, sludge or waste disposal, or drainage from raw material storage (40 C.F.R. §122.2).

Benchmark Monitoring: Monitoring requirements in the NPDES MSGP that provide a guideline for evaluating the overall effectiveness of a facility's stormwater control measures. Benchmark concentrations are not effluent limitations, but exceedances may trigger corrective action requirements.

Clean Water Act (CWA): The primary federal law in the United States governing water pollution, which established the National Pollutant Discharge Elimination System (NPDES) permit program and other water quality standards and regulations (33 U.S.C. §1251 et seq.).

Corrective Action: Steps that NPDES MSGP permittees must take to address any permit violations, stormwater control measure deficiencies, or other issues identified through inspections or monitoring results. Corrective actions may include modifying or replacing BMPs, conducting additional monitoring, or implementing other site-specific solutions.

Discharge: The addition of any pollutant or combination of pollutants to waters of the United States from any point source, or any addition of any pollutant or combination of pollutants to the waters of the contiguous zone or the ocean from any point source other than a vessel or other floating craft (40 C.F.R. §122.2).

Effluent Limitation: Any restriction imposed by the permitting authority on quantities, discharge rates, and concentrations of pollutants which are discharged from point sources into waters of the United States (40 C.F.R. §122.2).

Impaired Water: A water body that does not meet applicable water quality standards for one or more designated uses, as determined by a state or the EPA under Section 303(d) of the Clean Water Act.

Industrial Activity: The 11 categories of industrial activities specified in 40 C.F.R. §122.26(b)(14)(i)-(xi) that are subject to NPDES stormwater permitting requirements.

Multi-Sector General Permit (MSGP): A general NPDES permit that provides coverage for stormwater discharges associated with industrial activity in several sectors, streamlining the permitting process for facilities with similar operations and discharge characteristics.

National Pollutant Discharge Elimination System (NPDES): The national program for issuing, modifying, revoking and reissuing, terminating, monitoring and enforcing permits, and imposing and enforcing pretreatment requirements, under sections 307, 402, 318, and 405 of the Clean Water Act (40 C.F.R. §122.2).

Navigable Waters: Waters of the United States, including the territorial seas (33 U.S.C. §1362(7)).

Notice of Intent (NOI): A standardized form that facilities must submit to the permitting authority to obtain coverage under the NPDES MSGP, which collects information about the facility, its operations, and its stormwater discharges.

Outfall: A point source where a municipal separate storm sewer discharges to waters of the United States, which does not include open conveyances connecting two municipal separate storm sewers or pipes, tunnels, or other conveyances that connect segments of the same stream or other waters of the United States and are used to convey waters of the United States (40 C.F.R. §122.26(b)(9)).

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 (40 C.F.R. §122.2).

Pollutant: Dredged spoil, solid waste, incinerator residue, filter backwash, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt, and industrial, municipal, and agricultural waste discharged into water (40 C.F.R. §122.2).

Stormwater: Stormwater runoff, snow melt runoff, and surface runoff and drainage (40 C.F.R. §122.26(b)(13)).

Stormwater Discharge Associated with Industrial Activity: The discharge from any conveyance that is used for collecting and conveying stormwater and that is directly related to manufacturing, processing, or raw materials storage areas at an industrial plant (40 C.F.R. §122.26(b)(14)).

Stormwater Pollution Prevention Plan (SWPPP): A site-specific, written document that identifies potential sources of stormwater pollution at the construction site, describes practices to reduce pollutants in stormwater discharges from the construction site, and identifies procedures the operator will implement to comply with the terms and conditions of the NPDES MSGP (40 C.F.R. §122.26(b)(5)).

Total Maximum Daily Load (TMDL): The sum of the individual wasteload allocations for point sources and load allocations for nonpoint sources and natural background, which represents the maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards (40 C.F.R. §130.2(i)).

Visual Assessment: A quarterly inspection requirement in the NPDES MSGP that involves collecting a stormwater sample and visually observing it for color, odor, clarity, floating solids, settled solids, suspended solids, foam, oil sheen, and other indicators of stormwater pollution.

Wasteload Allocation: The portion of a receiving water's loading capacity that is allocated to one of its existing or future point sources of pollution (40 C.F.R. §130.2(h)).

Water Quality Standards: Provisions of state or federal law which consist of a designated use or uses for the waters of the United States and water quality criteria for such waters based on such uses (40 C.F.R. §131.3(i)).

Waters of the United States:

• Definition 1: All waters which are currently used, were used in the past, or may be susceptible to use in interstate or foreign commerce, including all waters which are subject to the ebb and flow of the tide (40 C.F.R. §122.2).
• Definition 2: All interstate waters, including interstate "wetlands" (40 C.F.R. §122.2).
• Definition 3: All other waters such as intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, "wetlands," sloughs, prairie potholes, wet meadows, playa lakes, or natural ponds the use, degradation, or destruction of which would affect or could affect interstate or foreign commerce (40 C.F.R. §122.2).

Wetlands: Those areas that are inundated or saturated by surface or groundwater 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 (40 C.F.R. §122.2).