Bypass and Upset Reporting
Bypasses (intentional or unintentional diversions around treatment) and upsets (unintentional excursions during compliant operation) have distinct regulatory treatment.
An upset is an unintentional excursion during an otherwise compliant period — typically not a permit violation if properly reported and documented; the plant can claim upset defense.
A bypass is a diversion of flow around a treatment process — typically prohibited, with specific exceptions for essential maintenance and unavoidable conditions.
Documenting the upset or bypass event (cause, duration, monitoring data, corrective actions) is essential to claiming the upset exception; without documentation, the excursion becomes a violation.
Even an unanticipated bypass requires notice — sometimes within 24 hours and a written follow-up report within 5 days. Check the permit for specific requirements.
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