It wasn't marked and no-one even knew it was there. I was exposing our conduit and stuck a side tooth through the pipe.
It took then forever to find the right valve,,, and another couple hours to discover they forgot to turn off the back-flow preventer.
We couldn't get all the water out of the hole because the conduit was acting like a dam, so I went in (up to my knees in water) and dug under the conduit.
After we got the pipe fixed, I had to buy a new pair of boots as the others took three days to dry.
When I was wearing those new boots, my left heel started hurting- which I attributed to new boots.
Turns out that it's the way I'm sitting on the backhoe while gingerly feeling for unknown utilities.