This has happened to me twice this year so I thought I would share.Digging a nice upper 30's signal I get down to about 12 inches and see a nice shiny object.They were stainless steel screw claps on black plastic pipe.The owner had know Idea that it was there I think that it was setup for gas grill of previous owner but was still loaded.I spent about 2 hours plugging this off at his garage where we found supply.Most pipes ,cables,water lines I can find and tell what they are by just following them.But not on plastic pipe.Although I did not puncture the plastic I gouged it enough to be unsafe.The plastic should have been yellow but weekend warriors use whatever is handy and they used black water pipe with stainless clamps.When digging/cutting a plug I am not a nice guy I am on my 3rd Lesche Digger I think it is the best and toughest equipment I have ever used and I use it for things that it was never suppose to do.Try not to do what I do dig carefully.I had the tools and knowledge to fix and repair even if I cut into this gas line on my truck most people do not.I know of an incident near Dundee,IL where contractor was bragging about easy 400 dollars he made for 15 minutes real work 3 hours total.Coin hunter cut 3/8 plastic irrigation line 6 inches deep and homeowner wanted it fixed right now ,about 7 bucks total in parts on a Saturday.I am more expensive than this contractor if I do side work, I usually go fishing or detecting though.