There was another FR thread this morning postulating that the plant was storing more ammonium nitrate than they were reporting because they did not have the required proper facilities and safety systems for the larger amount, being unwilling to pay the costs of those improvements.
However those are unconfirmed reports and may be inaccurate or false.
USA Today http://m.usatoday.com/article/news/2095817
They claimed 270 tons of Ammonium Nitrate. (What kind of ton - the 2000 lb/ton?) 540,000 lbs of Am Nitrate? That would have to be in the two large buildings.
Presuming the round buildings North side were grain storage.
If true, How big a volume is that?
From USA Today, we get the Adair Grain Inc 2012 Tier 2 Report - Via msnbcmedia.
Reporting period Jan 1 to Dec 31 2012. Printed April 18, 2013
http://msnbcmedia.msn.com/i/msnbc/Sections/NEWS/Adair%20Grain%20Inc%202012%20Tier%202%20Report.pdf