Was digging holes for planting some really nice Thuja Nigra's. As always had the yard marked for utilities AND had the homeowner advise of possible line locations. All going very well and running ahead of schedule. As I was (hand) digging one of the holes all of a sudden SSSSSSSSSSSSSS followed by wonderful smell of rotten eggs. OH $hit!!!!! followed by various other expletives. a closer inspection revealed a 1/2" hdpe black plastic pipe. Realizing this was not the main gas line, I found a small shut off valve. Turns out line was for an out door NG grill.