A long and completely speculative post concerning a situation about which we are never likely to learn the full story:
I remain a bit skeptical that just general dirty conditions could account for the amount of salmonella-tainted product found coming out of the Georgia plant. This is because in most cases nut production lines are largely closed to environmental contamination and because the first step in the process -- roasting at high temperature -- basically sterilizes the nuts. So the plant can be dirty, but "inside" the process, you have a continuous flow of "clean" material.
Never having been in the PCA facility, and not having seen their product flow, I'm talking through my hat, but I think that some of their internal practices spread contamination around and made the problem much worse.
The most obvious examples are the tests from 1/24/08 and 1/25/08, and the test from 9/24/08 and 9/26/08. In those cases, there was a positive test on granulated nuts, followed by a positive test on peanut paste. When you granulate nuts the nuts are passed through screens to separate the pieces based on size. You are left with too big, too small, and just right. One wouldn't want to waste the too big or too small -- they would go right into the peanut butter or peanut paste lines. One could also appropriately and routinely move product from the peanut paste line to the peanut butter line. So, once PCA had a positive result on granulated nuts, the contamination could easily be spread to other lines in the ordinary course of business.
So, if the granulated nuts were the source of at least some of the positive tests for peanut paste, and perhaps for peanut butter, how did they get contaminated?
Poor storage of roasted nuts in a generally nasty environment could do it, but I can think of a couple of other ways.
One would be "totes." Totes for raw peanuts are big sacks that hold 2000 pounds of nuts. When we move nuts from our oil roasting to our packaging equipment, we use very expensive covered stainless steel totes. But if one really wanted to save money, one could perhaps re-use fabric totes that had previously been used to hold raw product.
Another way would be processing contaminated roasted peanuts purchased by PCA from another source. According to some press accounts, PCA was always looking for a deal on raw peanuts. But it is also possible to buy roasted peanuts. And to find them on a deal. So, were I the FDA, I'd want to trace back upstream from PCA to see what I could find.
Finally, I thought of floor scrap. It is almost impossible, when granulating, to keep nuts from flying all over the place. Once they hit the floor, they should go straight into the trash. But an inspector would have to get awfully lucky to catch someone sweeping them up and dumping them back into the process.
None of these possibilities, of course, are mutually exclusive.