What POTW and CUPA Inspectors Check at California Facilities
Two different agencies can show up at a California facility and ask similar questions. The POTW (Publicly Owned Treatment Works, your local sanitation district) inspects under your wastewater discharge permit. The CUPA is your local Certified Unified Program Agency, which depending on the jurisdiction may be a fire department, county environmental health agency, or another local agency. CUPAs inspect your hazardous materials and hazardous waste programs. They are separate inspections under separate authorities, but the overlap is real. A waste stream that one inspector sees as a discharge question, the other often sees as a determination question.
Two different agencies can show up at a California facility and ask similar questions. The POTW (Publicly Owned Treatment Works, your local sanitation district) inspects under your wastewater discharge permit. The CUPA is your local Certified Unified Program Agency, which depending on the jurisdiction may be a fire department, county environmental health agency, or another local agency. CUPAs inspect your hazardous materials and hazardous waste programs. They are separate inspections under separate authorities, but the overlap is real. A waste stream that one inspector sees as a discharge question, the other often sees as a determination question.
This piece walks through what each inspector typically asks for and where common discharge violations and waste findings cluster. If you have already received a notice, the checklist toward the bottom is where to start. For a complete overview, see our industrial wastewater discharge permit guide.
The Two Inspection Tracks
POTW inspectors verify your facility is operating within the conditions of its industrial wastewater discharge permit. Their authority comes from the federal pretreatment program (40 CFR Part 403), enforced locally by the sanitation district that issued your permit.
CUPA inspectors verify hazardous materials and hazardous waste compliance under California law, including 22 CCR Division 4.5 for hazardous waste, the HMBP (Hazardous Materials Business Plan) program, and the local fire code. CUPAs vary by jurisdiction. Depending on the county or city, the CUPA may sit inside a fire department, an environmental health department, or another local agency.
The two inspections can run independently in the same year. In some districts they line up around the same compliance review window.
What a POTW Inspector Looks For
When the POTW walks a facility, the inspector typically asks for:
- The current discharge permit on site, including all conditions and attachments.
- Recent self-monitoring reports (SMRs) and any baseline monitoring reports the permit requires.
- The current slug discharge control plan, where one is required. Many permits require it, and many facilities do not realize it is a permit condition until the inspector asks for it.
- A Toxic Organic Management Plan (TOMP), if the permit calls for one.
- The 12-month water balance and process-flow drawings, plus any updates since the application.
- Floor drain locations, the pretreatment system, and the spill containment around it.
- Sample collection points and chain-of-custody records.
Common wastewater discharge violations cluster in a few places. SMRs submitted late, or missing parameters. A slug plan that has not been updated since the chemical inventory changed. A discharge above a permit limit after a process upgrade nobody flagged to the district. A floor drain plumbed somewhere it should not be. When we walk a facility before an inspection, floor drains and the difference between what the SMR shows and what the process actually generates are the first two things we check.
What a CUPA Inspector Looks For
On the hazardous waste side, a CUPA inspector verifies the facility has documented its waste streams correctly and is managing them under the right rules. The inspector typically asks for:
A written hazardous waste determination for every solid and liquid waste stream the facility produces.
The facility’s EPA ID number and current generator status.
Recent manifests, with land disposal restriction (LDR) paperwork attached where required.
Container labels showing accumulation start dates, hazardous waste markings, and accurate contents.
The designated accumulation area, with the right accumulation clock for the generator status.
An HMBP and CERS (the state’s online environmental reporting portal) submittal that matches what is actually on site.
Any tanks holding hazardous waste, and the most recent tank certification.
Common waste findings: determinations that were never written, or never revisited after a process change. Containers without start dates. An accumulation area no longer where the HMBP says it is. A waste stream managed as non-hazardous when California’s lower thresholds under 22 CCR §66261.24 would classify it as hazardous. A determination relying on a Safety Data Sheet alone for a waste stream that needs sampling and analysis.
Where the Inspections Overlap: Sewer or Ship
The crossover question both inspectors care about is whether a given waste stream should go down the drain under the wastewater discharge permit or leave the facility as manifested hazardous waste under the EPA ID. The POTW wants nothing prohibited reaching the sewer. The CUPA wants waste that should be manifested actually manifested.
We have seen this play out in the field. A facility’s lab report shows the wastewater is non-hazardous. The inspector reads the report and requests further testing through the California hierarchy: TTLC, then STLC, then TCLP. Sometimes the further testing confirms non-hazardous. Sometimes it shifts the answer, and the waste stream that was going down the drain now needs an EPA ID and a manifest.
Our hazardous waste determination guide goes deeper on classification.
Common Findings Checklist
Use this list to self-check before either inspector arrives.
| Area | What to verify |
|---|---|
| Discharge permit | Current permit on site, with all conditions and attachments |
| Self-monitoring | SMRs submitted on the required cadence, with all parameters sampled |
| Slug plan | A current slug discharge control plan, updated for the chemicals actually on site |
| TOMP | Toxic Organic Management Plan present if the permit requires one |
| Water balance | 12-month water balance and process-flow drawings updated for any process changes |
| Waste determinations | Written determination for every waste stream, revisited when processes changed |
| EPA ID and generator status | EPA ID current; generator status reflects actual generation volumes |
| Manifests | Manifests on file with LDR paperwork where required |
| Container labels | Accumulation start dates, hazardous waste markings, accurate contents |
| HMBP and CERS | Inventory on file matches what is on site; site maps current |
| Tanks | Treatment and waste tanks have current certifications |
If you cannot tick every box, the list also tells you which inspector will find which finding first.
When the Inspector Asks for “Further Testing”
An inspector asking for further testing is not, by itself, a violation. It is a request for evidence. The facility has to respond with sampling and analysis that either confirms the current classification or supports a new one. Doing this correctly matters. The California testing hierarchy proceeds in a specific order, and the wrong sequence wastes time and lab budget. We scope testing in the order most likely to settle the question, then write a determination report a regulator can defend. Every determination goes through a senior technical review before it leaves our office.
Our self-monitoring and baseline monitoring reports piece covers the reporting side of POTW compliance.
Next Steps
If a POTW or CUPA inspector has been at your facility, or is scheduled to be, the first move is to read the notice and pull the documents the inspector is asking for. The second move is to call before the response deadline, not after.
Inspector asking about your treatment tanks? Tank certification for wastewater treatment units →
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BSY started working with CDMS last year after our in-house EHS person departed the company. CDMS reviewed our existing operational permits as well as any additional Federal, State and Local regulations that could apply and helped us to create a comprehensive compliance calendar to track regulatory deadlines and submittal due dates. The CDMS team does an excellent job of tracking everything and can be relied upon to complete the forms accurately and assist with submittals, allowing me to focus on our business.
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