“It’s fairly common knowledge that most states require notifying their “dig safe” agency before excavation work (keep in mind “excavation” can be post-holes for a fence or deck as well as larger digs like trenches or a foundation.) Where I live it’s both on-line and on the phone, 811. And it’s free. They even run ads on the radio–good reminders actually.”
Click below to read more from Mark on ‘old house web.’