Before a substantial change in wastewater volume or pollutant character, notify the control authority and the receiving treatment utility if they are different. Compare the proposed process, chemicals, flows and pretreatment with the existing permit, then obtain the instructions or revised approval required. A plumbing connection that fits physically does not establish permission for a changed industrial discharge.
What does the federal rule require?
Under 40 CFR 403.12(j), all industrial users must promptly notify the control authority in advance of a substantial change in discharge volume or pollutant character. They also notify the publicly owned treatment works if it is not the control authority. The paragraph expressly includes the listed or characteristic hazardous wastes addressed by its notification provisions.
The rule does not give every facility one universal number of advance days in this paragraph. The local permit and utility process can add requirements. Ask the authority what information, review and permit amendment apply before scheduling startup.
How should you describe the proposed change?
Make a before-and-after list the authority can evaluate:
| Item | Information to establish |
|---|---|
| Process | Existing operation and proposed equipment or activity |
| Chemicals | Products, safety data and how they enter wastewater |
| Flow | Expected volume, peak batches and discharge schedule |
| Pollutants | Known changes in concentration or character |
| Pretreatment | Existing capacity and proposed control changes |
| Connections | The affected discharge point and drawing references |
Mark estimates as estimates. Ask the responsible designer or environmental professional to develop missing technical information. Do not infer that a smaller fixture drain means a smaller regulatory impact.
How does this relate to plumbing approval?
Phoenix's industrial program says construction drawings and engineering design manuals for industrial manufacturing or servicing facilities require its review before submittal to Planning and Development. Industrial discharge review and a plumbing permit answer related but different questions. Ask both authorities how the proposed scope moves through their processes.
Arrange any revised sampling plan and update the reporting file and responsible signatory. Keep the existing permit, submitted change description and authority response together. An unexpected harmful release instead calls for immediate incident notification, rather than treating it as a late version of the planned-change letter.