I've mined a private berm and it is quite a bit of work. All the non-magnum pistol rounds and most of the 223 rifle rounds were in the first 5 to 6 inches.
As for lead poisoning - most people very much over-blow this threat. Don't smelt indoors, don't eat or drink while smelting or casting. Don't use any smelting gear for cooking later. Don't do any smelting or casting in your kitchen.
I've been casting lead for some 2 decades now and I've had my lead level tested and have been pronounced in good health with no elevated lead levels.
So mining a berm is not something I have a fear will give me lead poisoning.
In my experience, the biggest concern, besides deforming the berm, that range owners seem to have is what's done with the contaminated scrap - i.e. the copper jackets. Typical answer is to put that back into the berm.
If you have a smelting pot cooking over an open fire pit - flux it with saw-dust, and cast ingots there, you can put the jacket pieces back where you found them in the berm and you aren't materially changing anything except recycling the bulk of the lead. I make round ingots in small muffin tins picked up at goodwill.
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