Just don’t put the dirt on the container itself! Them bad boys been known to buckle under dirt. I’d drop a few several feet underground, encased in a concrete barrier/box, with walls say, 3 - 4 foot thick? Maybe a nice ventilation system? :D
They float as well, if your water table comes up they will float out of the dirt. I plan on two feet of reinforced concrete above them for ballast and support then three feet of dirt for radiation hardness. For a total of 5 feet.