Please Wait...


PT Notes

EPA RFI - Worst-Case Release Scenario for Multiple Small Vessels

PT Notes is a series of topical technical notes provided periodically by Primatech for your benefit. Please feel free to provide feedback.

On July 24, 2014, the U.S. Environmental Protection Agency (EPA) announced a Request for Information (RFI) seeking comments on potential revisions to its Risk Management Program (RMP) regulations and related programs to modernize its regulations. Multiple issues were addressed in the RFI.

One of the issues addresses quantity requirements of the worst-case release scenario for processes involving small vessels stored together. The RMP rule requires the owner or operator to determine a worst-case release quantity for a process. EPA believes that in most cases the current requirements result in a reasonable estimate of worst-case releases, based on a review of past RMP submissions and facility inspections. However, EPA has questions about whether a different approach would better characterize the potential process hazards and associated risks for certain categories of facilities, such as chemical warehouses where large numbers of regulated chemical containers are stored closely together. This issue is of particular concern where each storage container may contain only a few pounds of a regulated substance, but numerous such containers are stored in close proximity to one another. EPA listed numerous incidents in the RFI involving such situations.

EPA is seeking information on whether to revise the RMP rule to account better for processes involving numerous small vessels stored together, such as on pallets,
cylinder racks, and in groups. EPA is soliciting comments on whether including the entire quantity in one location or one process, instead of just the single largest vessel or pipe, would better represent the true worst-case scenario. Also, EPA is requesting comments on whether there are ways of grouping vessels or pipes short of including all the vessels or pipes at a facility that would be appropriate for worst-case scenario analysis. Additionally, EPA is interested in receiving information on whether worst-case scenario requirements should account for the potential cascading effects of separate facilities that are interconnected (e.g. a manufacturer that provides product to an adjacent source through an interconnecting pipeline).

Questions posed by EPA on this issue include:

  1. Should EPA revise the RMP rule to require the owner or operator of any regulated process involving numerous small containers stored together to consider as the worst-case release quantity the sum of the quantity of all containers in the process, or a subset of such containers, or the containers within one storage area of the process?
  2. Would revising the worst-case scenario quantity determination requirement in this manner better represent the true worst-case scenario for such processes?
  3. Would this change promote stronger process safety controls and help prevent accidents?
  4. In situations where numerous small containers are stored together, are there any kinds of protective barriers or other methods of storage that would reduce the likelihood of a release from one container causing additional releases from adjacent or nearby containers? Should such barriers or storage methods be incorporated into the worst-case scenario requirements of the RMP rule, and, if so, how? Would revising the determination of the worst-case release quantity in the RMP rule cause any type of additional burden on facilities where large amounts of chemicals are stored together?
  5. If EPA were to revise the RMP rule to take into account numerous small vessels being stored together, what types/kinds of vessels should be covered? Should there be any limits on the size of containers subject to the aggregation requirement? What would such limits be based upon? Similarly, should a specific distance between vessels be established in order to consider them as grouped together for purposes of worst-case scenario calculations? What would that distance be based upon?
  6. Should EPA revise the RMP rule to require the owner or operator of a regulated process to consider the potential for worst-case release scenarios to involve adjacent facilities, or other nearby facilities, that are interconnected through pipelines? Would this change raise any confidentiality or security issues? How would EPA adjust its worst-case scenario modeling requirements to account for such a change?
  7. What would be the economic impacts of modifying the worst-case scenario analysis requirements as discussed above? Are there any special circumstances involving small entities that EPA should consider with respect to worst-case scenario analysis?

Further details on this issue are provided in EPA's RFI which can be accessed by clicking here.

Back to PT Notes