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Concept · term

NPDES

National Pollutant Discharge Elimination SystemNPDES permit

The Clean Water Act permit program that sets and enforces pollutant limits on point-source discharges to surface water.

[verified]
  • water
  • permitting

The National Pollutant Discharge Elimination System is the Clean Water Act program that licenses point-source discharges to waters of the United States. An NPDES permit names the outfall and receiving water, caps each regulated pollutant with numeric effluent limits, and sets the monitoring and reporting requirements the permittee must meet — chiefly by filing the discharge monitoring report.

In Ohio the program is delegated to the Ohio EPA, which issues NPDES permits under state authority; a new or expanded source also needs a permit to install before construction. The permit's fact sheet is the platform's primary source for a receiving water's design low flow (the 7Q10) and the assimilative capacity available to dilute a load — the same denominators that a large new consumptive cooling withdrawal would draw down.

Where a receiving water is impaired, the permit's limits are meant to implement the water body's total maximum daily load through a point-source wasteload allocation. Compliance history — inspections, violations, and any significant non-compliance flag — is public through EPA's ECHO.

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