VALE identified the need to address ground levels of the reject bins that did not allow for free drainage of stormwater, reject coal runoff and dust suppression water.
Damage to the reject coal overflow concrete bunkers also needed urgent attention, as did sections of the gravel roads leading directly to and from the two reject bins.
The situation was exacerbated by the continual drainage of water from the elevated silos, regular spillages of wet discard coal either directly from the silos or the bins of the haulage trucks, and standing water not draining away.
Additional risks included potential damage to unprotected and exposed feed conveyor support structures from passing vehicles and the need to remove risks associated with pedestrian movement in areas where large haul trucks were operating.
Three large concrete slabs were constructed just outside the two reject bins and tied into the existing concrete works to create a single monolithic structure. This provided a firm entry and exit surface for the trucks to enter and exit the loading position. Located directly in front of the reject bins, they were constructed on top and an extensive foundation doweled into the existing concrete structures to transfer the heavy loads.
Retaining walls and pedestrian bridge
Two retaining walls were built on either side of the second slab in front of the first reject bin to create a clear delineated vehicle route and to control levels allowing for the free drainage of surface water. A 3m high retaining wall was built to form an “elevated pedestrian-only island” between the two reject bins.
To access the pedestrian island, a steel pedestrian bridge crossing the path of the haul trucks was built. The bridge erected between the first retaining wall and the raised platform now provides mine personnel with a safer means of accessing the two reject bin silo structures.
A new emergency overflow bunker, including a concrete slab, as well as buttressed reinforced concrete walls, was constructed. Notably, both the walls and floor slab contain cast-in railway track rails to provide protection during the loading operations.
Concrete barriers were precast on site and placed in strategic location in the coal reject area and around the conveyor support columns on the approach to the reject bins.