It was stated that he put them in the oil barrels to cover up the smell. I would also assume he thought it was a pretty good place to hide them. Jmo
I remember reading that, too. I wonder if this was something LE thought, or if it was something CW actually stated.
I think CW thought the tanks were a heck of a good place. Perhaps experts in LE know of other cases where a crude oil tank was used, and/or absent a confession in this case, would have thought to look in the tanks because of CW's job and his GPS. IDK.