A fast and non-destructive way to safely locate and expose underground utilities.  Here, high pressure air is used to break up the soil, which is then vacuumed into a tank. Hydro excavation is used in difficult soil conditions where pressurized water breaks up the soil which is then vacuumed into a tank. This is also commonly known as potholing, hydro-digging, hydro-trenching or soft digging. [Source]