A) Endpoints

• Toxics: Use the toxic endpoints given in Appendix A of the Risk Management Program regulation.
• Flammables: Flammables: For the worst case, use an overpressure of 1 psi explosion. For the alternative, use a radiant heat/exposure time of 5kw/m2 for 40 seconds.

B) Wind Speed/Atmospheric Stability

For each accidental release, document:

• Date, time, and release duration.
• Chemical(s) released.
• Estimated quantity released in pounds.
• Type of release and the source.
• Weather conditions, if known.
• On-site impacts.
• Off-site impacts, if known.
• Initiating event and contributing factors, if known.
• Whether offsite responders were notified, if known.
• Process or operational changes as a result of the release.

• EPA's Chemical Accident Prevention and Risk Management Planning (RMP) Page
• General Duty Clause (EPA, 2009)
• EPA's Industry Guidance Website 
  • Operators of Water Treatment Systems

Facilities that have more than the threshold quantity (TQ) of a 112(r) listed "regulated substance" in a single process must develop and implement a risk management program, by June 21, 1999, as specified by the rule. In terms of the regulation, "process" means manufacturing, storing, distributing, handling, or using a regulated substance in any way.

In the hazard assessment section of the Risk Management Program, facilities must evaluate the possible consequences of an accidental release to nearby communities, schools, hospitals, recreational facilities, and other public and environmentally sensitive areas by predicting the "worst-case" and "alternative" (i.e., more likely) release scenarios. These scenarios can be demonstrated using computer-based models. Facilities must also document past accidents that have occurred at the facility for the last five years.

In 1996, the EPA issued a rule aimed at preventing accidental releases and reducing the severity of releases that do occur. The rule, Risk Management Program Rule under Section 112(r) of the Clean Air Act Amendment of 1990, has been amended and updated on several occasions.

Amendments to Rule

Accidental Release Prevention Requirements: Risk Management Program Requirements Under Clean Air Act Section 112(r)(7); Amendments to the Submission Schedule and Data Requirements; Final Rule. (69 FR 18819)

• Background Concentrations for Modeling Purposes (revised 12/18/2023)
• Digital Terrain Data: National Elevation Dataset (NED) for use with AERMOD
• Download AERMET Data Using Our Interactive Map
• Download Ozone Data for use in AERMOD Tier 3 NO2 modeli

• For worst case and alternative scenarios, the facility must have on site the description of the vessel/pipeline and substance selected as worst case, all assumptions and parameters used, and the rationale behind said assumptions. Documentation should include the anticipated effect the mitigation and controls have on the release rate.
• Document the release quantity, release rate, and duration.
• Methodology used to determine endpoints.
• Data used to estimate population and environmental receptors affected.

For each toxic substance, one alternative scenario must be submitted. For example, if a facility has 5 toxic substances, the Offsite Consequence Analysis must have one worst-case analysis and five alternative scenarios.

For each flammable substance, one alternative scenario must be submitted to represent all flammables. For example, if a facility has 6 flammable substances, the Offsite Consequence Analysis must have one worst-case analysis and one alternative scenario for the worst-case flammable substance.

An integrated prevention program must be developed that includes establishing standard operating and safety procedures, proper training for employees, preventive maintenance procedures, investigating and documenting accidents, and performing periodic safety audits at the facility.