Ann: Presentation Noosa Mining Conference, page-5

The key takeaway was that they threw out all the low grade underground resources - stuff that was between 0.5% and 1% Cu (never going to be economic for underground mining in Australia) and some smaller low grade resources in open pits that were marginal. By tossing out this marginal stuff they are left with less tonnes but at a higher grade so the economics must be better, from what I picked up they also tossed out one of the lead-copper orebodies so that saved having to build a separate lead circuit at the concentrator.

Some of these decisions must have been tough, as previous workers and studies may have included this in the project and there would be a some money and effort put into these marginal parts of the orebodies that have been reclassified as waste, but rather than having a "perfect" project that never gets finance/built or falls over at the first short term decline in copper prices they have gone for an imperfect but more robust project with less tonnes at a higher grade that might get built and make a profit.