The do say the best place to find a mine is under an existing...

The do say the best place to find a mine is under an existing mine .
As the ramp for the open pit haul trucks gets deeper it means that ramp can also substitute for a decline (haul road ) which would be needed for an underground mine , therefore much of the CAPEX (guessing around $40,000 a vertical meter) has been paid for by the open cut ramp which can then access the portal an the bottom of an opencut mine for underground mining assuming there is economic ore there .

In saying that it is best to initially pick the low hanging fruit in this case that is ore down to 150 meters from surface which can be accessed by an opencut mine and exploration drill costs are obviously lower when drilling from surface than for an deeper underground mine .

Also the topography has flat valleys and relatively dry , so haul roads from satellite pits are cheap to install and trucking ore is relatively low cost so makes satellite pits from up to 70kms away (ie Mt Magnet to the East) a viable option