As I suspected, the US Chemical Safety board has gotten to the site where we saw the Crude/Asphalt mixture spewing out of the large white storage tank (and ignited).. the Fluidic Catalytic Cracker EXPLODED. The explosion sent pieces of metal into the tank, blowing a large hole into it.
Most problems with a Fluidic Catalytic Cracking unit will happen during powering up or powering down (the heating or cooling), and the highly explosive and very very sensitive azide products or possibly fulminates of mercury coat and clump on the walls. I would say it is a failing of the design.. Each refinery that has a Fluidic Catalytic Cracking unit must go through cleaning cycles periodically, where the dangerous explosive coating (on the inside) has to be carefully removed.
My best guess is, because Husky inherited the problem from the previous owner, the Fluidic Catalytic Cracking unit (FCCU) was in need of long overdue maintenance.. During the powering down/cooling cycle the explosion appears to have happened.
Most likely, if another refinery has a poorly maintained (cost cutting for instance) FCCU, if there is a feed pipeline or stock tank nearby the Unit during one of the explosions, the same situation could happen. An explosive shrapnel laden detonation can send deadly and dangerous metal pieces and whatever liquids/gases are present everywhere in the vicinity. The resultant fires no doubt would release the toxic clouds as was happening with the Superior Wisconsin Husky Energy refinery incident.
The plant owners/operators have no business cutting corners when it comes to maintenance and safety.
EPA currently says, "All Clear" as far as the "air quality" goes. That took a while to clear today being May 3rd 2018.
There remains the issue of the inspectors "determining" why the FCCU failed. The statement included they were wondering why the "metal" was weak.
None of these units can withstand a large explosion if there is a substantial buildup of the highly unstable residues within the FCCU.
https://www.wpr.org/safety-board-sup...-cracking-unit
There is now a concern about potential water pollution:
David Morrison, the EPA’s on-scene coordinator, is still overseeing Husky’s air quality monitoring in Superior and another agency coordinator is working remotely on air quality data.
"The EPA has been involved in the development of the company's long-term air monitoring plan," said EPA spokeswoman Rachel Bassler in a statement. "EPA remains ready to return with air sampling capabilities should another event occur."
The DNR is also overseeing water cleanup and an oil boom that has been placed in Newton Creek to prevent any residual oil or firefighting product from reaching the Hog Island Inlet.
Air monitoring updates are available on the Douglas County Health Department website.