Water Technology (WT) were commissioned by BHP Mitsui Coal Pty Ltd (BMC) to develop a diversion strategy at the South Walker Creek (SWC) mine to secure mining access to the Mulgrave coal resource area associated with the Kemmis Pit. The Kemmis Pit area represents one of the northern operation areas at the SWC mine and the Mulgrave coal resource is understood to be a high value coal reserve. The Mulgrave coal reserve is transected by Carborough and Walker Creeks. Carborough and Walker Creeks are major tributary systems of the larger Bee Creek catchment, which ultimately flows to the Fitzroy River via the Isaac and Mackenzie Rivers to discharge to the Coral Sea in Rockhampton. The project scope has included the identification of the preferred creek diversion options; Surface water assessments involving hydrological and hydraulic analysis; and fluvial geomorphologic assessments of the waterway systems.
In total, some twenty diversion channel alignment options were identified as part of the study. The alignment options considered a range of scenarios involving channel length, channel grade, diversion take-off and re-connection locations, etc. The diversion options also included short term versus long-term diversion strategies, with the short-term options generally representing the shorter length diversion options. The alignments reflect the nature of the key controls at the site and specifically the local topographical conditions whereby the options have been structured to minimise excavation quantities. The initial diversion options were considered by BMC’s Project Steering Committee and a process of shortlisting of the options was undertaken. Conceptual diversion channel arrangements including channel form and shape and earthwork quantities for five shortlisted options were prepared for consideration by BMC. Two preferred diversion options were ultimately chosen to proceed with more rigorous assessments.