Dendrobium Ventilation Shafts

NSW
BHP
2008
11km

access road designed and constructed

2

shafts drilled and lined

174

composite steel liners installed

3

bridges constructed

Abergeldie was engaged by BHP Billiton to deliver the Dendrobium Ventilation Shafts project. The project comprised two shafts, each reaching a depth of 270m with finished diameters of 4m and 5m. The shafts were blind-bored from the surface and lined using remote methods. The shafts were completed before the underground tunnels reached the location of the shaft bottom. Given the absence of existing infrastructure, purpose-built facilities were established for the project. 

Scope of works 

The works included: 

  • The design and construction of an 11km access road. 
  • The construction of an electrical substation. 
  • The design and construction of 3 bridges.
  • Site preparation, including clearing, fencing, and the establishment of a site compound. 
  • Installation of the water reticulation system from Cordeaux Dam.
  • The construction of settling ponds, essential for the reverse circulation process. 
  • The construction of a precast yard and the design and building of 174 composite steel and concrete liner segments. 
  • Foundations for fans, shaft collar, and the drill rig. 

Navigating environmental sensitivity with innovative blind bore shaft drilling

The blind bore shaft drilling method, an innovative alternative to traditional approaches, involves surface drilling using the assembly’s weight to exert force through rock cutters. Water circulation forces spoil to the surface through the drilling pipe and into circulation ponds. A specially designed soft rock cutter, seamlessly fitting into standard ring-type cutter housings, proved effective in drilling rates and cutter wear. 

The site was highly environmentally sensitive with the construction taking place within the Sydney Catchment Authority (SCA) area and approximately 500m from Cordeaux Dam, a major SCA water storage facility. Despite these challenges, there were nil environmental or safety incidents throughout the life of the project.