CalARP Seismic Assessment Requirements in California
California sits on top of a working fault network, so it is the one state where an accidental release prevention program has to assume the ground may move.
California sits on top of a working fault network, so it is the one state where an accidental release prevention program has to assume the ground may move. The CalARP regulation reflects that. Local administering agencies frequently require facilities with covered processes to include a seismic assessment with the Risk Management Plan. This is especially common when those processes contain anhydrous ammonia, chlorine, or other regulated substances in pressurized vessels, large unbraced tanks, or piping runs near faults.
This piece covers what a CalARP seismic assessment is, when an agency typically requires one, what the deliverable contains, and what CDMS handles on a seismic project. For the broader picture of who needs a plan and what else goes inside it, see our CalARP and Risk Management Plan compliance guide for California.
Why CalARP Includes Seismic at All
The CalARP regulation requires every Process Hazard Analysis to address external events, both natural and human-caused. In California, the most consequential natural external event is an earthquake. A toxic release triggered by an unbraced vessel tipping over, a piping connection failing at a flexible joint, or a relief device shifting off-line during ground motion is exactly the kind of scenario the PHA is supposed to surface.
That is where seismic assessment comes in. It is the engineering analysis behind the “seismic” entry on the external-events line of the PHA, and it gives the agency, and your operations team, confidence that the covered process will not be the source of an offsite release after a credible earthquake.
CalARP does not impose one statewide seismic-study format. The regulation requires every PHA to consider external events including natural hazards, and in California the dominant natural hazard is earthquake. Many California administering agencies ask for a seismic assessment where earthquake-related failure could contribute to an accidental release. The local administering agency, which may be a CUPA (Certified Unified Program Agency, often a fire department hazmat program or county environmental health department), or another participating agency, sets the expected scope. Confirm the local agency’s expected seismic scope before drafting.
When Agencies Typically Require a Seismic Assessment
Agency expectations vary, but the situations that almost always trigger a request for a seismic study are predictable:
- New CalARP plan submittal in a county with active fault zones, where the administering agency has standing seismic-study requirements.
- Five-year plan renewal when the prior plan either lacked a seismic section or relied on an analysis that is now significantly out of date. See CalARP 5-year updates: renewing your Risk Management Plan for the broader update cycle.
- Process or equipment change that introduces new pressure vessels, larger tanks, or piping runs in covered service.
- Plan deficiency response when the CUPA returned the prior submittal and seismic was flagged as missing or inadequate. See common CalARP plan deficiencies and how CUPAs review submittals for the broader review-and-revision pattern.
- Recommendations from the PHA that identify a credible seismic-induced release scenario, particularly for unbraced or older equipment.
What the Seismic Assessment Covers
A CalARP seismic assessment is narrower than a building seismic evaluation. The focus is the covered process, not the entire facility. A typical scope includes:
| Item | What the assessment addresses |
|---|---|
| Site seismicity | Ground motion expected at the facility based on the local fault setting, soil profile, and the design basis the agency requires |
| Covered process inventory | Every vessel, tank, piping segment, and supporting structure that holds a regulated substance above its threshold quantity |
| Equipment anchorage | Whether tanks, vessels, and skid-mounted process equipment are anchored or braced to resist horizontal and vertical seismic loads |
| Piping and connections | Flexibility, supports, and connection design at points where seismic displacement would otherwise concentrate stress |
| Relief, isolation, and emergency shutoff | Whether emergency shutoffs and relief paths remain available after a credible earthquake |
| Adjacent hazards | Non-covered equipment, structures, or stored materials that could fail and impact covered process equipment (“falling-on” hazards) |
| Findings and recommendations | Specific deficiencies and recommended corrective actions, prioritized by risk |
The deliverable is a written report that goes into the appendices of the RMP submittal. It cross-references the PHA external-events section and ties any recommended actions into the prevention program. For how that prevention program is structured, see what’s inside a CalARP/RMP submittal: the required elements.
The seismic study also feeds the offsite consequence analysis. If a credible seismic-induced release scenario exists, it should be evaluated in the alternative release scenario portion of the OCA, with realistic source-term assumptions.
What CDMS Does on a CalARP Seismic Project
We have built seismic assessments into CalARP and RMP plans across California for more than 30 years. A typical project follows this sequence:
Agency confirmation.
We confirm with the administering agency what seismic scope is required for the specific facility and process. Requirements vary, and the conversation up front avoids a deficient submittal later.
Site walkthrough.
Our team comes to your facility, walks the covered processes with your operations staff, and inventories every vessel, tank, piping segment, and support structure that holds a regulated substance above threshold.
Equipment review.
We review anchorage, bracing, flexibility, and connection design against the loading the local seismicity implies. P&IDs (piping and instrumentation diagrams), equipment data sheets, and any prior structural calculations are pulled in here.
Adjacent-hazard survey.
We look at what could fall on, displace, or shear off a covered process: unbraced racking, overhead piping, non-covered tanks, and similar.
Documentation.
A written report with findings, recommendations, and the cross-references the PHA and OCA sections need. The report goes into the plan’s appendix.
Agency response support.
If the reviewer comes back with questions or asks for additional analysis, CDMS handles the revision cycle inside the same engagement.
The most common issue we surface during a seismic walkthrough is anchorage that was sized for an earlier code edition and never re-evaluated after later equipment changes. The most common reason a plan gets returned for seismic is a study that exists but does not actually cover every piece of equipment in the covered process, or a study that pre-dates a major facility change. Both are correctable.
For ammonia refrigeration systems, where pressure vessels and long piping runs make seismic exposure a recurring topic, the assessment overlaps with mechanical integrity work covered in ammonia refrigeration and CalARP compliance in California. For how the seismic findings feed into the PHA, see process hazard analysis (PHA/HAZOP) for CalARP & RMP.
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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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