The blind bore shaft drilling method is an innovative construction technique and an alternative to the traditional methods of sinking deep large diameter shafts (raise boring and conventional drill and blast shaft sinking). It involves drilling from the surface using the weight of the drilling assembly to apply force through rock cutters on the drill head. Water circulation is used to force the spoil up to the surface through the drilling pipe and into circulation ponds.
A soft rock cutter was developed to deal with soft but abrasive rock encountered on the project. This cutter could fit into the housings for standard ring type cutters, removing the need to make major modifications to the drilling head. The soft rock cutter proved to be highly effective both in drilling rates and the wear rate on the cutters.
The site was nominated as highly environmentally sensitive due to construction within Sydney Catchment Authority (SCA) area and around 500 metres from Cordeaux Dam, a major SCA water storage facility. There were no environmental or safety incidents through the life of the project.
