Tiered Permit Closure Certification: Closing a Treatment Unit
Most facility-closure conversations are about closing an entire site. This piece is about something narrower: closing one permitted hazardous waste treatment unit while the rest of the facility keeps running.
Most facility-closure conversations are about closing an entire site. This piece is about something narrower: closing one permitted hazardous waste treatment unit while the rest of the facility keeps running. In California, that path lives under the state’s Tiered Permitting program, and finishing it cleanly means producing a Professional Engineer (PE) stamped closure certification that DTSC (the Department of Toxic Substances Control) will accept (required for Permit-by-Rule closures).
If you are closing a whole facility, the California facility closure plans process is what you need. If you are only retiring a single treatment unit (a tank, a containment system, a treatment process), you are in tiered permit closure certification territory. The two paths share a regulatory backbone but the deliverables are different. For where this fits in the broader picture, see our facility changes in California guide.
What a Tiered Permit Closure Certification Is
California’s Tiered Permitting program lets facilities treat their own hazardous waste on site without a full DTSC permit, operating under one of three lower tiers: Conditionally Authorized (CA), Permit by Rule (PBR), or Conditionally Exempt (CE). Each tier carries its own operating, recordkeeping, and closure obligations under Title 22 of the California Code of Regulations, Division 4.5.
When a facility wants to stop operating a unit, simply unplugging the equipment is not enough. DTSC requires a documented closure: the unit is decontaminated, the work is verified, and a California-registered Professional Engineer signs a certification that the unit has been closed in accordance with the regulations. That PE-stamped certification is what lets DTSC remove the unit from the facility’s tiered permitting status. This PE-certification requirement applies specifically to PBR closures under CCR 67450.3(c)(11)(G). Conditionally Authorized units require written notification upon closure completion (certified mail to CUPA and DTSC), and Conditionally Exempt units have their own notification requirements. Confirm the applicable requirements for the specific tier. The certification is not a one-page sign-off; it is a report covering the unit description, closure procedures performed, sampling and verification results, waste disposition, and the PE’s stamp and signature.
When You Need One
The trigger is usually operational, not regulatory. The most common scenarios:
Replacing an old treatment unit with a new one and needing to formally retire the old one.
Changing a process so on-site treatment is no longer needed.
Downsizing and consolidating treatment into fewer units.
Getting a DTSC or CUPA (Certified Unified Program Agency, which may be a county environmental health department, fire department, or another local agency depending on jurisdiction) inquiry about a unit that has not operated in years and is still on the tiered permit.
Preparing for a tiered permit renewal and wanting inactive units off the books first.
The trigger we see most often during Comprehensive Compliance Management visits is the last two: a unit stopped being used long ago, and nobody filed the closure paperwork. It is still legally part of the facility’s permit, which means the facility is still on the hook for its compliance even though it is not being used.
What Tiered Permitting Closure Actually Requires
DTSC’s closure requirements for tiered permitting facilities lay out a set of deliverables that varies by tier. The general structure looks like this:
| Tier | Closure Plan | Closure Cost Estimate | Financial Assurance (if cost above DTSC threshold) | Environmental Assessment | Notification to DTSC + Property Owners |
|---|---|---|---|---|---|
| Conditionally Authorized (CA) | Required | Required | Required if applicable | Required | Required |
| Permit by Rule (PBR) | Required | Required | Required if applicable | Required | Required (agency + property owners) |
| Conditionally Exempt (CE) | Varies by CE sub-tier and unit; confirm with the local CUPA or DTSC | Varies by CE sub-tier and unit | Varies by CE sub-tier and unit | Varies by CE sub-tier and unit | Varies by CE sub-tier and unit |
The closure plan describes how the unit will be decontaminated, what waste will be generated and disposed, and how the work will be verified. The closure cost estimate documents what closing the unit would cost a third party to perform; where the applicable tier and unit-specific rules require financial assurance, the facility has to put an approved mechanism in place. The environmental assessment captures the physical condition of the unit and surrounding area at the time of closure. Requirements for a Conditionally Exempt unit depend on the CE sub-tier and unit, so confirm the applicable closure requirements with the local CUPA or DTSC.
In practice, most unit closures we handle involve a tank or containment system. Under Title 22, Sections 66265.191–193, tanks and containment systems used to manage hazardous waste have specific integrity-evaluation requirements that feed into the closure assessment, and the PE looks at those records (or runs the evaluation) before stamping the certification.
The Process We Run
A typical unit-closure certification engagement runs in this order:
Document review.
We pull operating records, treatment records, waste manifests, tank or containment integrity records, and the current tiered permitting notification to understand what the unit treated and what its closure baseline looks like.
Site visit.
A CDMS consultant walks the unit and assesses physical condition, residue, the surrounding area, and any decontamination already done. A clean, already-decontaminated unit is a different engagement from one that still holds residue.
Closure plan and closure cost estimate (if not already prepared).
For CA and PBR units, these documents are drafted or confirmed against current regulations and the actual closure scope. The cost estimate determines whether financial assurance is in play.
Decontamination and verification.
The unit is cleaned per the closure plan. Sampling (wipe, swab, or rinse depending on the unit type) verifies the cleaning. Where tanks or containment systems are involved, integrity evaluation under Title 22 §66265.191–193 is part of the verification record.
Report preparation.
We draft the closure certification report: facility and unit description, regulatory citations, closure procedures performed, verification results, waste disposition, and the PE’s findings.
PE certification.
A California-registered Professional Engineer reviews the report and stamps the certification. The PE stamp is what makes the deliverable acceptable to DTSC.
Notification and submission.
California regulations require notifying DTSC (and, for PBR units, property owners) at least 15 days before closure completion. We coordinate that notification and submit the amended Facility-Specific Notification that removes the unit from the tiered permit.
The closure certification becomes part of the facility’s permanent closure record for that unit and should be retained with the tiered-permitting file and related hazardous-waste records.
Where Unit Closure Crosses Into Full Facility Closure
If contamination has spread beyond the unit, or if the facility is closing in addition to retiring the unit, the engagement shifts toward a full facility closure plan and report under CUPA review. We cover that distinction in detail in facility closure vs. unit closure: which one your situation requires.
Why a PE Stamp Matters
For PBR units, a closure that is not PE-certified is not a closed unit in DTSC’s eyes. CA and CE tiers have different closure documentation requirements. Facilities sometimes assume that ceasing operations, draining the tank, and updating internal records is enough. It is not. Without the stamped certification, the unit stays on the tiered permitting roster, the facility carries forward liability for its compliance history, and any future buyer’s environmental due diligence will surface the open unit as a risk.
What to Have Ready Before You Call
A short, accurate first conversation saves us all time. Have the following at hand: the current tiered permitting notification (the document filed with DTSC listing each unit and its tier), the unit’s tier (CA, PBR, or CE), a description of the unit and what waste streams it handled, whether decontamination has already been done, and what is driving the closure.
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.
Speak with a CDMS EHS expert
Tell us about your facility and your deadline. You’ll get a clear read on what applies and a scoped plan to handle it.