Someone has pointed out something that I over looked.
That's a good input...do it now while there is fuel for the back hoe.
When your neighbors ask WTH you are doing you DONT tell them they are pre-dug graves. Tell them that you are building individual fighting positions (just kidding) or better yet, future site of your septic system run off or animal waste disposal of parts that the slaughterhouse doesn't want. Just be sure to dig 30 degrees outside LOS of LEO satellites and in full shade, under a tree when digging, or at night. Satellites are GREAT at spotting freshly dug ground, even at the shallow grave level.