I understand the disclaimer about underground utilities but I don't know where you are located at but here if you hit an underground line of any sort you are responsible for the cost of fixing it and the cost of the local emergency personal that come out to the job if they are notified. I have my stumps marked if there is any question of me hitting something other then a gutter down spout.
:agree2:
No amount of disclaimers will absolve you of liability for public utilities. In fact, in Mo & Ks, only the contractor doing the digging (or grinding) can make the call to get the utility locate. They won't talk to the property owner unless that is who is doing the digging.
On the other hand, if you dig up the gas line to their patio grill, that disclaimer might come in real handy.