Toning for Utilities
The contractor should be diligent to identify, locate, and verify the nearby underground utilities prior to digging the shafts and bursting. The contractor must contact the one state One Call center to have representatives of the nearby utilities come to the site and mark the existing utilities on the ground surface. Then the contractor has to verify the exact location and depth of these utilities via careful excavation. Manual excavation may be needed for the last few inches from the existing utilities to avoid damaging this utility. Vacuum excavation is an excellent tool to expose utilities with minimum surface excavation and minimum risk to the existing utility.
Underground utilities that are in moderate condition are unlikely to be damaged by vibrations at distances of greater than 2.5 feet from the bursting head in small (less than 12 inch in diameter) typical pneumatic pipe bursting operations (Atalah 1998). The safe distance for large diameter bursting (up to 24 inch) is approximately seven feet (Atalah 2006). It has also been reported that ground displacements are unlikely to cause problems at distances greater than 2-3 diameters from the pipe alignment (Rogers 1995). Utilities that are closer to the bursting head than these distances should be exposed prior to bursting so the vibration from the bursting operation would not affect the utility in question.