Looking at the OS situation closer regards Bruce's comments and...

Looking at the OS situation closer regards Bruce's comments and the plant design I get the following:

"As previously disclosed additional oversize material has resulted in approximately 75% of the expected spiral feed delivered to the Wet Concentrator Plant (WCP)."... so we only know that spiral feed (undersize sand after OS screening and desliming) is running at 75% of DFS assumptions per tonne ore. By definition then, the spirals are only ~75% capacity given they were designed for 33% more feed than the 75% currently.

First OS is removed at the mining stage by DMU. I thought/hoped that much of the blocky ore OS could be removed there ahead of being pumped to WCP Screen pre-spirals... maybe not on second thoughts. Adjusting the DMU to pump more than nameplate ore to the WCP including 2-12mm OS is unreasonable, unless all the extra OS is >12mmm blocky and can be screened out early.

The second OS removal step is 2-12mm in the WCP Screen, and Bruce specifically talks to only 75% of expected feed to the spirals, so very specifically there is much extra OS in the 2-12mm fraction. Extra screening should be easily and cheaply added to the WCP to handle more than expected 2-12mm OS. The WCP screens are unlikely to be a LT limiting factor on spiral feed and thus production. If the DMU is pumping nameplate <12mm capacity to WCP screens, but that slurry has 25% more than expected 2-12mm OS, then the DMU in-pit is the limiting factor in reaching 100% of spirals design feed.

Either way, more OS is a bad thing because mining an extra 33% overburden and ore to reach 100% of spirals feed will add to costs even if the DMU could run above nameplate to make up for lower undersize per tonne of ore mined (which it probably can't). The DMU will top out at 1250t/hr or whatever, hopefully the majority of extra OS can be screened pre-DMU, pumping 'DFS % OS %' to WCP. If the OS issue is predominantly 2-12mm in the DMU pumped slurry, then the solution requires another or larger DMU imo.



"Within the total tph of ore mined material, if the mismatch in sizing occurs mainly between the coarse OS and the waste sand fraction, the VHM sand fraction will remain relatively constant in absolute terms as tph to the CUP and design criterion."... assume you mean if the extra OS is from low-VHM sand and the 75% spiral feed contains close to 100% of the DFS predicted VHM then we are sweet, and OS isn;t a bad thing? Yes, upside that's been mentioned might be that the OS is lower HM grade than the Usize, which can be calculated from the ore mined THM and OS figures when they are released. By my calculations there is lower HM in the OS than US fraction, waiting for Jun Qtrly to see if the trend persists. OS will certainly have some HM grade, so this upside can only go part way to mitigating 25% loss in US per tonne of ore mined imo...