This Sunday at church brought me a very interesting recollection from a retired 06 Nav describing his days as a C-123 squadron maintenance officer at Dyess after Vietnam. The parallel is obvious - whatever drifts below the Dumpster's cargo deck stays there...maybe forever. Grain, mixed repeatedly with water coming in through normal flight ops, did exactly what Agent Orange did...it stayed there until some unfortunate bunch of corrosion control specialists got stuck cleaning the goop out.
As hard as this project with the C-123 "Victory Garden" was, cleaning dioxin out of the airplane was far, far more difficult. It settled everywhere, coated everything, soaked into everything, and eventually, as Patches showed at the USAF Museum, the metal had to be scraped clean of paint, special solvents used, and then the results were still questionable after three professional efforts by decontamination experts.
Removing Agent Orange residue can be a nearly-impossible situation and there certainly is
the likelihood of Agent Orange and other military herbicide residue continuing to contaminate an aircraft.
I can appreciate the difficulty of trying to clean up the C-123 aircraft by maintenance folks. During my rated supplement maintenance tour at Dyess in 1973-75 we had six aircraft in Africa doing famine relief hauling grain in floor loaded bags. They were a little dusty when they came home but we cleaned them up and they went back into the fleet. When the first of those aircraft hit a major inspection where the floor had to come up in the cargo compartment I got a panic call from the phase dock chief (I was the maintenance control officer) to come down and see what they had found. There was four to six inches of wet grain in the bottom of the aircraft with sprouts growing out of it.
Three problems: what was the weight and balance of the aircraft with all that wet grain in it, the obvious threat of corrosion and it was foreign grain and presented an agricultural inspection issue. We bagged the grain and took it to the fire department burn pit and burned it under supervision. Then the maintenance folks had to do detailed cleaning of the whole length of the cargo compartment in the belly of the aircraft using dental picks to clean out all the crevices, after which the areas were recoated with zinc chromate.
The cleaning was a terrible job and took forever. Liquid Agent Orange, settled into these areas and eventually dried, would be nearly impossible to eliminate without extensive decontamination beyond the capabilties of any Air Force base.
As a maintenance officer, I find it perfectly reasonable that military herbicides did the same thing as did the grain, once released by filling/unfilling operations or combat damage. The residue remaining after evaporation would have settled in the lowest parts of the aircraft, except for where it soaked into surfaces such as wood and leater, or where it dried.