Ann: Greater Westralia Mining Area - Mineral Resource Update, page-86

It depends on the stoping methodology how they run the chevron etc, this is making a lot of assumptions but I would say they need to be about 3 levels below the production stope say 20m between levels at 1:7 down 140m in the decline, plus ore development stockpiles etc of anywhere between 3-500m per level, ventilation rises escapeways all are significant expenses so you probably have about 2-3months of development before you get any decent tonnes out.