Criteria for selecting alternative release scenarios

As part of the hazard assessment, owners and operators of Program 2 and Program 3 covered processes must identify and analyze alternative release scenarios (40 CFR §68.28). What criteria should be used when selecting an alternative release scenario?

The owner or operator of a stationary source subject to the risk management program regulations at 40 CFR Part 68 must analyze one alternative release scenario to represent all flammables in a covered process and one alternative release scenario for each toxic in a covered process. The owner or operator must choose a scenario that is more likely to occur than the worst-case release scenario and that will reach an endpoint off site (40 CFR §68.28 (b)), unless no such scenario exists. Even if no alternative release scenario reaches an off-site endpoint, the source is still required to perform an alternative release scenario that is more likely to occur than the worst-case scenario. When selecting an alternative release scenario, the source shall consider releases that have been documented in the five-year accident history and failure scenarios identified through the process hazard analysis or hazard review (40 CFR §68.28). Sources should consider several types of events listed under 40 CFR §68.28(b)(2), where applicable.