Any best practices for holes in the ground? I can imagine that metal detectors and various animals change the threat model, but I suspect there are also unknown unknowns at play here.
Diamonds were worthless until De Beers paid a marketing agency to make the public think they are valuable.
In other words, salt the surrounding area with lightly buried worthless coins, nuts, bolts or metal scraps and anyone trying to find your loot will give up.
Ground-penetrating radar is a different beast, but also has its limitations: https://en.wikipedia.org/wiki/Ground-penetrating_radar#Limit...
This sounds like a fun thought exercise. No idea who we are protecting against but some factors might be:
- Moisture. The containers need to be completely sealed from moisture and have resistance to acid from the soil.
- Metal detector. Perhaps this could be mitigated using a skid-steer with an auger drill attachment? Some of the larger skid-steers can use an 80 inch bit. Excavators can use even larger bits and drill at angles to get under solid objects. Rock auger bits can get through some rocks. Layers of gravel might obscure detection from ground penetrating radar.
- Location should be obfuscated by trees to avoid satellite and aircraft imaging from Keyhole/Google/Others.
- Accessibility. If there is a few feed of rocks above the container and a rope passes through the rocks, then retrieval is less likely to damage the container and one would not need dig as deep for extraction.
- Drill numerous holes and find some other use for them whilst singing One of these things is not like the other
For anti-metal detection, ideal spot would be atop/near a buried junkyard. Once they've gone to the trouble of excavating a rusted Dodge Neon, interlopers are not inclined to dig there again.
The investigators tear apart the backyard and find nothing. The alleged terrorist then lets his wife know the backyard is prep'd for this year's potato planting.