Underground wiring is used for running electricity to security lights, landscaping lights, ponds or other decorative landscaping ornaments and to storage sheds or outlet boxes.
If you are running wiring underground, you need to use conduit to protect the wiring.
The conduit should be at least twelve inches underground and GFI protected with no more than twenty amps.
You have to use a GFI receptacle and a GFI breaker.
If you decide against a GFI breaker, you need to bury the UF cable at least twenty-four inches deep.
If you use PVN conduit, you will need to bury it eighteen inches or with steel conduit, you will need to bury it six inches.
Of course, you have to check with your particular building codes to see if the same requirements are the same as described above. Some areas have different requirements to meet the housing code.
If you do not meet the code requirements properly, you can be sited for violations, which can be costly. You will also have to remove the underground wiring and do it the correct way. This, in itself, could be costly for any homeowner.
It is always better to check the requirements and do the work the right way.
Professional, licensed, insured electricians are experienced in handling these issues and can ensure that you meet all safety and building code requirements.