Just a quick note – I hope to update this later.
The explosion in Texas has caused some reporters to imply that the company’s RMP filing for Anhydrous Ammonia was inaccurate because the “Worst Case Scenario” didn’t include an explosion of the Ammonia Nitrate at the facility.
The “Worst Case Scenario” isn’t something the facility gets to decide – it’s set in the LAW by the EPA at §68.25(c)(1)
“(c) Worst-case release scenario—toxic gases. (1) For regulated toxic substances that are normally gases at ambient temperature and handled as a gas or as a liquid under pressure, the owner or operator shall assume that the quantity in the vessel or pipe, as determined under paragraph (b) of this section, is released as a gas over 10 minutes. The release rate shall be assumed to be the total quantity divided by 10 unless passive mitigation systems are in place.”
It would seem that the facility was taking advantage of the “retail exemption” in the PSM rule to avoid being a PSM covered process as they filed their RMP as a L2 process. Note that Ammonia Nitrate is not a covered chemical under the PSM or RMP rule.
Update: John Astad has a good roundup of how widespread this issue can be.