The South Walker Creek open cut coal mine is located in the Bowen Basin in Queensland, 35km from Nebo.  In late 2018 ALLROADS were contracted to deliver works for the HV/LV Separation Project and also the decommissioning of C-Dam Rapid Release Outlets to present a safe environment for Light Vehicle access across the site through the mitigation of contact with Heavy Vehicles. 

The HV/LV Separation project included:

• Constructing approximately 7.8km of new site access roadway;

• Constructing roadway intersections for crossing the Haul Road to provide access by Light Vehicles to Pit Ramps, Explosives Compound and Coal Stockpiles;

• Constructing additional multi-plate drainage culverts beneath the new embankments for the new Light Vehicle roadway and associated drainage works.

The rapid release Dam was made up of five relieving pipes that required a hydrotite seal installed inside and outside the inlet of the pipes with a mass concrete plug to encase the pipes. This was then filled with a capping layer to tie into the existing surrounds. Dewatering of the Dam was required prior to the works, with a retaining coffer dam then installed upstream of the inlets in order to construct a working platform to complete the works. 

A major challenge encountered in delivering the works was the unsuitable ground (high plasticity clay & sand) that was uncovered following the strip of the natural surface. ALLROADS developed a new fill strategy including bridging layers and alternative borrow sources to reduce the requirement to remove and replace unsuitable fill and therefore providing cost and time savings to BHP.