Hazardous Waste Determination in California
Every California facility that generates waste has to answer the same question for each waste stream: is this hazardous, or is it not? The answer drives how the waste gets labeled, how long it can sit on site, how it leaves the property, and which reports the facility owes to its CUPA (your local Certified Unified Program Agency, which depending on the jurisdiction may be a fire department, county environmental health agency, or another local agency), DTSC (the Department of Toxic Substances Control, the state agency that regulates hazardous waste), and CalEPA (the California Environmental Protection Agency). That answer is the hazardous waste determination.
Every California facility that generates waste has to answer the same question for each waste stream: is this hazardous, or is it not? The answer drives how the waste gets labeled, how long it can sit on site, how it leaves the property, and which reports the facility owes to its CUPA (your local Certified Unified Program Agency, which depending on the jurisdiction may be a fire department, county environmental health agency, or another local agency), DTSC (the Department of Toxic Substances Control, the state agency that regulates hazardous waste), and CalEPA (the California Environmental Protection Agency). That answer is the hazardous waste determination.
A determination is a written record. It documents what the waste is, how the facility evaluated it, the regulatory basis for the conclusion, and who made the call. California treats it as foundational: your Hazardous Materials Business Plan (HMBP), biennial generator report, tiered permitting status, and SB 14 source reduction plan all rest on it. If the determination is wrong, everything downstream is wrong with it.
This piece covers what a determination is, how California classifies waste differently from federal RCRA, how the testing hierarchy works, and when a determination has to be redone. For how waste decisions fit alongside permitted sewer discharge (the “sewer or ship?” question), see our industrial wastewater discharge permit guide for California facilities.
What a Hazardous Waste Determination Is
Federal RCRA (40 CFR Part 261) and California’s Title 22 (22 CCR Division 4.5) both require generators to determine whether each solid or liquid waste they produce is hazardous. The determination runs through four characteristics:
| Characteristic | What it means | Common examples |
|---|---|---|
| Ignitability | The waste catches fire under defined conditions (flash point under 140°F for liquids, or a flammable solid) | Spent solvents, unused paint thinners, isopropyl alcohol rinses |
| Corrosivity | Aqueous waste with pH ≤ 2 or ≥ 12.5, or a liquid that corrodes steel above a defined rate | Spent acid baths, alkaline cleaners, etching solutions |
| Reactivity | Unstable, reacts violently with water, generates toxic gases, or is otherwise dangerously reactive | Cyanide- or sulfide-bearing waste, water-reactive metals, certain peroxides |
| Toxicity | Contains constituents above regulatory thresholds when tested | Metal-bearing sludges, plating waste, lab chemicals, contaminated absorbents |
A waste only has to meet one characteristic to be hazardous. Wastes can also be hazardous because they appear on a regulatory list (F-, K-, P-, or U-listed wastes federally, plus additional California-listed wastes) or because they qualify as a special waste under 22 CCR §66261.124. A determination considers all of these paths before concluding the waste is non-hazardous.
Determinations are site-specific and process-specific. They belong to the waste stream as the facility currently generates it. They do not transfer when a building changes hands and do not stay valid when a process changes.
Why California Is Stricter Than Federal RCRA
A waste can be non-hazardous under federal RCRA and hazardous under California law. This is one of the most common surprises for newly acquired facilities that inherited determinations written under a federal-only frame.
Title 22 expands the federal universe in three ways. More constituents are regulated. Several RCRA-regulated constituents have stricter California limits, so a waste that passes the federal TCLP can still fail the California test. And California recognizes a separate non-RCRA hazardous category. Wastes that are hazardous only under California law still require manifesting, an EPA ID, and a permitted disposal facility. They are not non-hazardous.
For a side-by-side breakdown, see California vs. federal hazardous waste rules under Title 22 and RCRA.
The California Testing Hierarchy: TTLC, STLC, and TCLP
For toxicity, California uses a sequenced testing approach against the limits in 22 CCR §66261.24. Running every test on every constituent up front would cost a fortune and almost never changes the outcome. The hierarchy moves from broadest to most involved only as the data requires.
TTLC (Total Threshold Limit Concentration).
Total concentration of a constituent in the waste. If total concentration equals or exceeds the TTLC value, the waste is hazardous for that constituent. If total concentration is below the TTLC limit but high enough that soluble leaching could exceed the STLC (a common screening rule: total above 10 times the STLC threshold), STLC testing is the next step.
STLC (Soluble Threshold Limit Concentration).
How much of the constituent leaches out using the California Waste Extraction Test (WET). Below the STLC limit, the waste is non-hazardous for that constituent under California rules. Above it, California-hazardous.
TCLP (Toxicity Characteristic Leaching Procedure).
The federal leach test. Used to determine whether the waste is also RCRA-hazardous, which affects manifesting and disposal options.
Additional assessments exist (such as the 96-hour fish bioassay), but most determinations conclude at TTLC or STLC for metals because going further rarely changes the answer and adds significant lab cost. For a deeper walkthrough, see how California classifies waste by toxicity using TTLC, STLC, and TCLP.
When a Determination Has to Be Made (or Redone)
A determination is not a one-time deliverable. California treats it as a living record tied to the process that generates the waste. The following situations all trigger a new or updated determination:
- A new waste stream appears from a new chemical, process, product line, or one-time cleanup.
- The process generating the waste changes. New raw materials, a chemistry change, or new equipment that alters what ends up in the waste.
- The facility changes hands. Determinations do not transfer with ownership. A new owner inherits the waste, not the paperwork.
- A CUPA or POTW inspector requests further documentation. Classic version: the current lab report says non-hazardous, the inspector asks for STLC or TCLP follow-up, and the original determination needs to be reopened.
- Determination records are missing. California requires generators to retain them, and inspectors will ask to see them. “We don’t have one” is a finding in itself.
- A waste was being shipped based on assumption. When in doubt, the generator must treat the waste as hazardous until a defensible determination says otherwise.
When we walk a facility for the first time, the most common deficiency we find is a waste stream that has been shipped for years on a generic profile with no underlying determination document on file. The second most common is a determination written for a process that no longer exists, because the equipment was replaced two years ago and nobody updated the paperwork.
What’s in a Determination Report
The “hazardous waste determination form” that shows up in search results is, in practice, a written report. For each waste stream it documents:
- The waste and the process that generates it
- The regulatory criteria evaluated (the four characteristics and any applicable listings)
- The data used to reach the conclusion: SDS review, process knowledge, and lab analyses where required
- The testing sequence followed (TTLC, STLC, TCLP as applicable) with the specific limits referenced
- The conclusion (RCRA-hazardous, California-only hazardous, or non-hazardous) with the waste codes that apply
- Personnel, dates, and supporting attachments (lab reports, SDSs, calculations)
Every determination report goes through a senior technical review before it leaves our office. Two sets of eyes on every determination is non-negotiable, because the cost of getting one wrong runs in both directions: shipping hazardous waste as non-hazardous is a regulatory and environmental problem, and treating non-hazardous waste as hazardous wastes money the facility doesn’t need to spend.
How CDMS Handles a Determination
There are two ways facilities engage us, depending on what’s already in hand. With full-service determination, our consultant walks the facility, identifies the waste streams at the point of generation, reviews SDSs and process information, collects samples where lab data is needed, coordinates the analysis, and writes the report. With report-only determination, the facility already has current lab data and SDS documentation, and we produce the report from what you have. This is common when an inspector has requested formal documentation for a waste that was previously handled informally.
For both paths, the testing approach is sequenced by what’s most likely to drive the classification. We test the most probable hazardous characteristic first and only proceed to the next test if the data requires it. That keeps lab costs in line with what the determination actually needs.
From there, the determination feeds the rest of the hazardous waste program. The waste codes go on the manifest; volumes flow into the biennial generator report and HMBP; the disposal pathway depends on whether the waste is RCRA or California-only. For how the determination connects to shipping, see from determination to disposal: EPA ID numbers, manifesting, and shipping hazardous waste. For whether a waste stream could be discharged to the sewer under a permit instead, see the sewer-or-ship decision for California facilities.
Trusted throughout California
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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