NAC459.95368. Analysis of alternative release scenarios.

     1. The owner or operator shall identify and analyze at least one alternative release scenario for each toxic highly hazardous substance that is used in a process and at least one alternative release scenario to represent all flammable highly hazardous substances or explosives that are used in processes.

     2. The facility may use the R.M.P. Guidance for Off-Site Consequence Analysis, which is adopted by reference pursuant to NAC 459.95528, to calculate any of the values required in this section.

     3. For each scenario required pursuant to subsection 1, the owner or operator shall select a scenario that:

     (a) Is more likely to occur than the worst-case release scenario developed pursuant to NAC 459.95366; and

     (b) Will reach an endpoint off-site. If no alternate release scenario will reach an endpoint off-site, then the owner or operator shall select the alternate release scenario with the most significant on-site impact.

     4. The owner or operator shall consider, without limitation and where applicable, scenarios in which:

     (a) A transfer hose releases because of splits or sudden uncoupling of the hose;

     (b) Process piping releases because of a failure at a flange, joint, weld, valve and valve seal, drain or bleed;

     (c) A process vessel or pump releases because of a crack or a failure of a seal, drain, bleed or plug;

     (d) A vessel overfills and spills, or overpressurizes and vents through a relief valve or rupture disc; and

     (e) A shipping container is mishandled and thereby breaks or is punctured leading to a spill.

     5. The owner or operator:

     (a) Shall use the appropriate parameters set forth in NAC 459.95364 to determine the distance to the endpoints;

     (b) May use:

          (1) The methodology provided in the R.M.P. Guidance for Off-Site Consequence Analysis, which is adopted by reference pursuant to NAC 459.95528; or

          (2) A commercially or publicly available technique for air dispersion modeling, if the technique accounts for the specified modeling conditions and is recognized in the industry as a current practice; and

     (c) May use a proprietary model that accounts for the modeling conditions if the owner or operator allows the Division access to the model and describes to local emergency planners, upon request, the features of the model and any differences from publicly available models.

     6. The owner or operator may consider active and passive mitigation systems for an alternative release scenario if the mitigation systems are capable of withstanding the event that triggered the release and still function as intended.

     7. When selecting the alternative release scenarios, the owner or operator shall consider, without limitation:

     (a) Any accidental release and any incident that was investigated pursuant to NAC 459.95429; and

     (b) The analyses performed pursuant to NAC 459.95414.

     (Added to NAC by Environmental Comm’n by R121-98, eff. 5-27-99; A by R137-04, 2-15-2005)