Ann: Annual Report to Shareholders, page-58

My comment about 'just' balancing out in steady state comes from the time it takes to relocate these units (typically several days) and the overburden removal job to be done before they get into the new location ore body. There isn't anything left after this happens to make up for the other two slugging away, well they better be! That there is little to no overburden at the moment helps while the breakdowns abate.

Having surplus feed requirement is just sensible, so average feed rates to the plant can be kept up as the balance may shift between DMU's for all sorts of reasons, so they can each take up a bit of slack. In some processes, extra capacity allows make-up to happen, typically by stockpiling. Here it is direct coupled to the WCP so the DMU's can't send more than the WCP can take. To put feed on the ground and pick it up again is very uneconomical, I doubt that would happen here.

You probably know this, but for the benefit of 'curious others', there is not some magic line in the sand where the grade or colour changes and we are into 'the good stuff'. It is a transition from really low to less low grades, all determined from geo drilling and then mined according to the plan, with GPS or other survey techniques to determine what is overburden and what should be processed. Then 'the WCP magic happens' and they see how they went. The only tool they have is to observe recoveries at WCP and figure out what it means for DMU / mining performance and act accordingly. I don't know how they would differentiate between DMU's, maybe shut one off for a short while then you know which has the poor (or good) recoveries and which has not found a good match between drilled and reality. Or, more likely, kept on keeping on when they should have moved on. Moving into guesswork here, and I am not a fan of that...