When to Revise OCA
The risk management program in 40 CFR Part 68 requires facilities to conduct an off-site consequence analysis (OCA) to provide information to state, local, and federal governments and the public about the potential consequences of an accidental chemical release. When does a facility need to revise its OCA?
The owner or operator of a stationary source subject to Part 68 shall review and update the OCA at least once every five years (§68.36(a)). Additionally, if changes in processes, quantities stored or handled, or any other aspect of the stationary source might reasonably be expected to increase or decrease the distance to the endpoint from a worst-case release scenario by a factor of two or more, the owner or operator shall complete a revised analysis within six months of the change and submit a revised risk management plan (RMP) (§68.36(b)). For example, if a facility increases the largest vessel size of a regulated substance, the distance to endpoint should be re-estimated. If the distance is at least doubled or halved, then the facility would need to update and resubmit the RMP. For most substances, the quantity that would be released would have to increase or decrease by more than a factor of five to double or halve the distance to endpoint.
Guidance for preparing or revising the OCA is available in Chapter 4 of the General Guidance on Risk Management Programs for Chemical Accident Prevention (EPA555-B-04-001) and the Risk Management Program Guidance for Offsite Consequence Analysis (EPA550-B-99-009).
These documents are available at the following URL: