Back reaming commences at the receiving trench. Close radio contact is maintained between the Hydro-vac truck crew and the drill operator. The pilot hole is 125mm Ø, the water main pipe diameter is 180mm, the back reamer reams out a 250mm Ø hole on the way back. The back reamer displaces the additional 125mm Ø of the borehole as cuttings suspended in the drilling fluid. This is the sediment laden slurry we see being discharged out of the bore hole alongside the pipeline.