There is some confusion above.
There are two facilities at Wirrida which have no relationship with each other.
One is the OZ minerals siding parallel to the loop, this is the mineral concentrate referred to which goes in container type kibbles to Port Adelaide where I understand they are unloaded by Rotainer.
Just north of the crossing loop there is a balloon loop which was developed by WPG for iron ore which was to have been unloaded at Port Pirie from the reinstated radium siding and barged out. This was the operation which was bought by OneSteel/ Arrium and the ore is taken to the new unloading loop at Whyalla. This is the service affected by the derailment.
In this view you can see the small balloon loop on the right. The haul road on the left os OZ, the one on the right is Arrium