Figuring out how deep into the ground pellets go

When I started airgunning, it was just a casual hobby, but now Im pretty much dedicated to it. Ive been just firing down into my yard from my second floor bedroom window, and never gave much thought to it until now - I dont really know how deep these pellets go. granted it depends on a lot of factors, just now makes me nervous about hitting a plumbing or utility line on accident, or sprinkler line.

Any thoughts? Im well on my to investing in pellet traps now, just looking for a ballpark guesstimate on how far down these puppies go.
 
Could hit a cable/coax line or any communcation line like fiber half-azz buried. Have your states Miss Utility mark your lines for your house, make up a story why (weather shelter, garden). Red is power, orange is communication, white or yellow is gas, blue is water. Marks can also be off by 1-2 feet depending on the chap that does the job. But earth would stop a pellet probably in 3 inches maximum, in loose topsoil.

If things are to code; code varied over the years and lines work their way up as runoff occurs. My power line to my house was only 9" deep...almost got killed and I had them marked (just thought they would be 2 feet down!) Good luck.