Safely exposing an underground facility is the best way to work within the tolerance zone. That way you know precisely where the underground facility is located, making it easier to avoid.
Before you can use mechanized digging equipment in a tolerance zone, you must verify the presence and location of the buried facility. There are many non-destructive methods to expose underground facilities including hand digging, vacuum excavation, pot holing and soft digging. If you must remove pavement or masonry, equipment can be used, but only to the depth of that pavement or masonry.
If you are unable to locate the facility after performing a reasonable search, contact the facility owner directly for help. Once the facility is located, mechanized digging equipment can be used.
If you will be exposing a facility during your excavation, you are required to provide adequate support and protection for it. An unsupported portion of a line can pull and distort a joint or splice that is out of sight. The damage can occur several feet up the line - underground - and you'd never see it.In addition, you are required to provide an adequate backfill upon completion.