CPSWQ key terms

An NPDES permit issued for stormwater discharges from construction sites that disturb one acre or more of land, or are part of a larger common plan of development disturbing that area. It sets effluent limits, best management practice requirements, and inspection and reporting duties.

A form submitted to the permitting authority by an operator declaring the intent to be covered by a general NPDES stormwater permit. Filing typically provides permit coverage after a waiting period and requires certification that a stormwater plan has been prepared.

A submission ending permit coverage once the site is finally stabilized and all stormwater discharges have ceased. Final stabilization generally means uniform vegetative cover or equivalent permanent measures on all disturbed areas.

A site-specific document identifying potential pollutant sources and the best management practices that will control them. It includes site maps, erosion and sediment controls, good housekeeping measures, inspection schedules, and responsible personnel.

A structural device, practice, or operational procedure used to prevent or reduce pollutant discharge in stormwater. Examples include silt fence, detention basins, sweeping, and spill kits. BMPs are selected based on site conditions and pollutant risk.

Measures that keep soil in place and prevent detachment by wind or water, such as mulching, hydroseeding, blankets, and slope drains. Preventing erosion is generally more effective and cheaper than capturing sediment after it mobilizes.

Practices that trap soil particles already suspended in runoff before the water leaves the site, such as silt fence, sediment basins, and check dams. These are a second line of defense behind erosion prevention.

A temporary impoundment that slows runoff so soil particles settle out before discharge. Design considers drainage area, storage volume, and dewatering method. It requires regular removal of accumulated sediment to remain effective.

The condition in which all soil-disturbing activities have permanently ceased and disturbed areas are covered with vegetation or other permanent cover that will persist. It is the trigger for terminating permit coverage.

Temporary or permanent covering of disturbed soil to reduce erosion. Temporary measures may include mulch or erosion blankets; permanent measures include established vegetation, pavement, or structural cover. Permits set deadlines measured in days after disturbance ceases.

The party with control over site plans, specifications, or daily activities who must obtain permit coverage. On construction sites, both the owner-developer and the general contractor may qualify, and each can be held responsible for compliance.

A person who knows the permit requirements and possesses the training or experience needed to conduct inspections and evaluate control measures. Permits specify who may inspect and what credentials or training they must hold.

A scheduled field review of stormwater controls and discharge points to confirm they are installed, functioning, and maintained. Findings are documented, and deficiencies trigger corrective action within permit-specified timeframes.

The repair, replacement, or redesign of a control measure or practice that failed or was inadequate. Permits require corrective actions to be completed within a set number of days after discovery and documented in the site records.

Removal of groundwater or accumulated water from an excavation or work area. Discharge must be managed through appropriate controls such as settling tanks or filter bags, and may require separate permit authorization depending on volume and quality.

The cloudiness of water caused by suspended particles that scatter light. It is a common field indicator of sediment pollution and is often subject to numeric limits or monitoring requirements in stormwater permits.

The mass concentration of particles suspended in water, determined by filtering a sample and weighing the dried residue. It is a standard pollutant measure for construction and industrial stormwater and a frequent benchmark in permits.

A conveyance or system of conveyances owned by a state, city, or other public entity that discharges to waters of the United States and is not part of a combined sewer. Operators must obtain NPDES permit coverage for these discharges.

A regulated municipal separate storm sewer system serving an urbanized area or designated area that is subject to the small MS4 general permit. It carries six minimum control measures and usually operates under a phase-based permit cycle.

The document describing how a regulated municipality will implement permit requirements, including measurable goals, responsible departments, and schedules. It is submitted with the permit application and updated each permit term.

The six program elements required of small MS4 permittees: public education and outreach, public participation, illicit discharge detection and elimination, construction site runoff control, post-construction runoff control, and pollution prevention for municipal operations.

A program to find and remove non-stormwater flows entering the storm sewer, such as sanitary sewage, wash water, or chemical dumping. It includes mapping, legal authority, field screening, and public reporting mechanisms.

Any discharge to a storm sewer that is not composed entirely of stormwater, with limited exceptions allowed by permit such as certain firefighting flows or uncontaminated groundwater. Identifying and eliminating these flows is a core municipal obligation.

The point where a storm sewer or drainage channel discharges to a receiving water body. Outfalls are monitored, screened, and mapped because they are the most direct location to detect pollution leaving a system.

Any discharge from a storm sewer outfall during dry conditions, which by definition cannot be entirely stormwater. Field crews screen these flows for indicators such as ammonia, surfactants, or chlorine to trace illicit sources.

Requirements that new development and redevelopment manage runoff after construction is complete, typically through infiltration, detention, or treatment controls. Programs also require long-term operation and maintenance of those controls.

A design approach that manages rainfall close to its source through infiltration, evapotranspiration, and reuse. Techniques include bioretention, permeable pavement, and rain gardens, aiming to mimic pre-development hydrology.

A network of natural and engineered features that absorb, store, and treat stormwater, such as vegetated swales, tree canopies, and constructed wetlands. It provides hydrologic and water quality benefits while often reducing conventional gray infrastructure costs.

A permanent structural practice installed to manage runoff volume, rate, or quality after development, such as a detention basin or bioretention cell. SCMs require inspection and maintenance for the life of the project.

The routine activities and records needed to keep stormwater controls functioning over time, such as cleaning catch basins, mowing basins, and repairing outlets. Municipal and industrial permits require documented O&M programs.

A yearly submission to the permitting authority summarizing permit compliance, program progress, monitoring results, and planned improvements. It is a primary accountability tool for municipal and industrial permittees.

An NPDES general permit covering stormwater discharges from regulated industrial facilities by sector. It typically requires a site-specific plan, pollutant monitoring, and comparison of results against benchmark values or numeric limits.

An optional conditional exclusion from industrial stormwater permit coverage for facilities where industrial materials and activities are not exposed to rain or runoff. It must be maintained and recertified periodically.

The condition in which industrial materials, equipment, or activities are open to precipitation or runoff. Exposure determines whether permit coverage is needed and drives which controls must be installed.

Sampling of stormwater discharges to compare results against non-enforceable benchmark concentrations that indicate whether controls are working. Exceedances typically trigger additional investigation, corrective action, or enhanced treatment rather than automatic violations.

A numeric or narrative restriction on the quantity, rate, or concentration of pollutants that may be discharged. Effluent limits are enforceable permit conditions, unlike benchmarks, and can be technology-based or water quality-based.

A specific enforceable value, such as a maximum concentration or mass, that a discharge must not exceed. It may be expressed as a daily maximum, monthly average, or other averaging period defined in the permit.

A calculation of the maximum pollutant amount a water body can receive and still meet water quality standards, allocated among sources. Stormwater permits in impaired watersheds may include limits or requirements consistent with the TMDL.

Additional permit conditions applied to particular industrial categories, such as landfills, scrap recycling, or transportation facilities. These reflect the pollutants and activities typical of each sector and may add monitoring or control obligations.

The lakes, rivers, streams, estuaries, or coastal waters into which stormwater discharges flow. Their designated uses and water quality standards drive permit limits and monitoring requirements.