Sewer or Ship? The California Waste Determination Decision
Most of the wastewater and waste calls we field come down to one question, even when the caller asks it differently: can this waste go down the drain under our wastewater discharge permit, or do we have to ship it out as hazardous waste under our EPA ID? It sounds simple. In practice it sits between two different programs, two different agencies, and two different sets of testing rules. Getting it wrong in either direction creates a problem.
Most of the wastewater and waste calls we field come down to one question, even when the caller asks it differently: can this waste go down the drain under our wastewater discharge permit, or do we have to ship it out as hazardous waste under our EPA ID? It sounds simple. In practice it sits between two different programs, two different agencies, and two different sets of testing rules. Getting it wrong in either direction creates a problem.
This piece walks through the sewer-or-ship decision the way we walk it with a client: what each path means in California, what drives the answer, why an inspector might tell a facility that “non-hazardous” lab data still isn’t enough, and how the comparison actually plays out. For the full mechanics of how California classifies a waste stream, see our hazardous waste determination guide for California facilities. For the broader permit picture, see the industrial wastewater discharge permit pillar.
What “Sewer” and “Ship” Actually Mean
The two paths are governed by separate programs.
Sewer means the wastewater leaves the facility through the sanitary sewer, under an industrial wastewater discharge permit issued by the local POTW (Publicly Owned Treatment Works, usually your city sanitation department or regional sanitation district). The federal frame is the Clean Water Act and 40 CFR Part 403 (the National Pretreatment Program). The local POTW sets the contaminant limits the discharge has to stay under. The facility may need to pretreat the wastewater first, and once the permit is in place, the obligations continue through self-monitoring reports, baseline monitoring, and a slug discharge control plan.
Ship means the waste leaves the facility as manifested hazardous waste under California’s hazardous waste rules, generally Title 22 (22 CCR Division 4.5), and the federal RCRA program. The facility needs an EPA ID number, a written hazardous waste determination for each stream, a permitted transporter, and a permitted disposal facility. DTSC (the Department of Toxic Substances Control) and the local CUPA (your Certified Unified Program Agency, which depending on the jurisdiction may be a fire department, county environmental health agency, or another local agency) enforce on the ground.
A given waste stream typically only belongs in one of those buckets. A few special cases (such as treatment in a permitted on-site treatment unit) sit between them, but for most facilities the decision is binary.
What Drives the Answer
Three things determine which path a waste stream belongs to.
What’s in the waste.
The four California hazardous waste characteristics under 22 CCR §66261.10–24: ignitability, corrosivity, reactivity, and toxicity. A waste only has to meet one to be hazardous. For toxicity, California uses sequenced testing against the limits in 22 CCR §66261.24, starting with Total Threshold Limit Concentration (TTLC), then Soluble Threshold Limit Concentration (STLC) using the California Waste Extraction Test (WET), and the federal Toxicity Characteristic Leaching Procedure (TCLP) where RCRA status matters. The deeper walkthrough lives in TTLC, STLC, and TCLP testing.
Whether the POTW will accept it.
Even when a stream is technically non-hazardous, the local POTW may refuse to take it. Most pretreatment ordinances set their own concentration limits, prohibit certain pollutants outright, and require the facility to demonstrate the discharge fits the permit. A non-hazardous label does not mean automatic sewer eligibility.
Whether the facility has the permits and pretreatment in place.
A stream that could legally be discharged still cannot go down the drain if the wastewater discharge permit doesn’t cover it, if the categorical limits would be exceeded, or if the pretreatment system isn’t designed for it.
The first piece is the determination question. The second and third are permit questions. All three have to line up before a waste stream becomes sewer-eligible.
“It Came Back Non-Hazardous, but the Inspector Wants More Testing”
This is the most common variation of the sewer-or-ship question that lands on our phone. A facility has lab data showing the wastewater (or a sludge, or a process stream) is non-hazardous. The inspector or POTW reviewer reads the report and asks for additional testing before signing off. STLC is the usual next step, sometimes TCLP after that.
That isn’t an arbitrary request. The first round of testing often covers totals (TTLC) only, which is enough to clear a stream that’s well below the California threshold but not enough to characterize a borderline result against the soluble (STLC) and leachate (TCLP) limits. The California testing hierarchy exists for exactly this reason. The inspector knows that and is asking the right question.
When we walk into that scenario, the first thing we do is read the existing lab report against the actual regulatory limits the inspector applied. The second is to confirm whether the current testing program has built-in re-test triggers (it usually doesn’t), so the next inspection doesn’t loop the facility through the same conversation. From there we scope the additional analysis with the testing sequence aligned to the most probable hazardous characteristic, not the full battery.
Sewer vs. Ship: How the Decision Compares
| Sewer (Discharge to POTW) | Ship (Manifested Hazardous Waste) | |
|---|---|---|
| Governed by | Clean Water Act, 40 CFR 403, Porter-Cologne Act, local POTW pretreatment ordinance | RCRA (40 CFR 261–262), California Title 22 (22 CCR Division 4.5) |
| Enforcer | Local POTW or sanitation district, with Regional Water Board oversight | DTSC and the local CUPA (fire department, county environmental health, or another local agency depending on the jurisdiction) |
| Required permit / number | Industrial wastewater discharge permit | EPA ID number |
| Required document for the stream | Permit limits, pretreatment plan where applicable, slug discharge control plan | Written hazardous waste determination, manifests, generator status records |
| Testing frame | POTW concentration limits, often categorical (metal finishing, electroplating, semiconductor, others) | TTLC, STLC, TCLP against 22 CCR §66261.24 limits |
| Ongoing obligations | Self-monitoring reports, baseline monitoring, TTO certification, slug plan | Manifesting, biennial generator report, HMBP, tiered permitting where it applies |
| Cost driver of getting it wrong | Illegal discharge: enforcement, surcharges, possible permit revocation | Treating non-hazardous waste as hazardous: unnecessary disposal cost and inflated generator status |
The two columns aren’t ranked in difficulty. Either path, done correctly, is manageable. The expensive outcome is treating the decision as obvious when it isn’t.
Why Getting the Decision Wrong Costs Both Ways
The sewer-or-ship call has equal downside in both directions.
Send a hazardous waste down the drain and the facility is looking at a pretreatment violation, a possible enforcement order from the POTW, and exposure under the Clean Water Act and Porter-Cologne. Repeated discharges raise the question of whether the permit gets revoked altogether.
Treat a non-hazardous waste as hazardous and the facility pays for manifested disposal it didn’t need, generates volumes that push it into a higher generator category (with the reporting and storage obligations that come with it), and locks in a cost structure that doesn’t go away on its own.
We see both ends regularly. Walk a facility for the first time and the most common finding is a waste stream being shipped on a generic profile with no determination in the file. The second most common is a stream being discharged under the assumption that “we’ve always done it this way” with no testing data to back it up. Neither is malicious. Both are the result of the decision being made once, years ago, by someone who is no longer at the facility.
How CDMS Handles the Decision
When a stream sits between the two paths, we work it from both sides. On the determination side, our consultant walks the facility and identifies where and how the waste is generated. We review SDSs (Safety Data Sheets) and process information, run the testing in sequence against the California limits that apply, and write the determination report. Every determination goes through senior technical review before it leaves the office, because the cost of getting it wrong runs in both directions and a second set of eyes catches what one set misses. On the permit side, we read the actual wastewater discharge permit (not the client’s recollection of it), match the stream against the POTW’s concentration limits, and confirm whether the discharge path is open. The output is a clear answer: this stream belongs in the sewer under your existing permit, or this stream has to ship as hazardous waste under your EPA ID, or this stream needs a permit modification before it can stay where it is. For how a hazardous-waste stream actually leaves the facility once classified, see from determination to disposal: EPA ID numbers, manifesting, and shipping.
Still deciding whether a permit applies? Do you need a wastewater discharge permit? →
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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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