Beware! On one job they were supposed to call 811 to have underground line marked before they started to dig. Their excuse was as long as they didn't dig closer than 2 feet they did not have to. The only 24 inch rule that 811 has (556.105 Procedures. — 5a) the utilities markings can be as far away as 2 feet from their lines.

Be careful, if they hit anything, you maybe responsible!