Injection hole centres 1 to 2m (no more than 2m) – At end of borehole, centres are larger of course!Injection hole angle 7 to 10° in top headingInjection hole angle 10° min in invert (depending on extent of rock de-stressing)Drilling starts in invertAdvisable to drill all holes the same lengthClean holes with water flushing – running drill rod in and out of hole (Very important)Water ingress measurement prior to groutingControl holes in face after groutingNormal tunnels = 2 to 4 control holes where anticipated in profileUrban tunnels (low water ingress) = 8 to 12 control holes 1m offset inside profileAll control holes are filled with grout prior to blasting forward advances