Cannington Mine – Watercourse diversion design, flood study and EIS support

BHP Billiton Cannington Mine is an underground operation which is proposed to expand to open cut operations. To allow development of the proposed open cut pit and associated infrastructure, diversion of a watercourse is required. Alluvium was engaged at an early stage in the process in order to design an appropriate watercourse diversion, in line with “Best Practice” and regulatory requirements. Baseline condition assessment of existing watercourses through the site was initially undertaken. Various concept designs were subsequently developed, with two options being progressed to functional design. Finally, the most suitable option was developed to detail design stage.

A flood study was also undertaken by Alluvium, in order to understand changes in flood dynamics caused by the proposed development, and to inform infrastructure design. This involved hydrologic modelling (rainfall runoff routing) of the catchment in order to obtain flow estimates for the 1000 year ARI and PMF events. These flows were then used within a 2 dimensional flood model for existing conditions and post development scenarios.

Diverting a watercourse around an open cut pit and waste rock dump poses many environmental issues, both during mine operation and in the long term post mine closure. As the diversion forms a critical component of the proposed mine expansion, particularly with respect to regulatory approval, Alluvium played a key role in the planning process, in particular the Environmental Impact Statement.