since the deposit are vertical and are open at depth, perhaps it would be worth while considering an underground operation with a common production shaft located in the middle of the two deposits? An UG operation would significantly cut down the amount of overburden and waste rock. It can also by-pass the (10-60m) barren sill which seems to limit the current depth of the pit to 200-300m. Sometimes a UG operation is more advantageous in various aspects, including environmental review (smaller footprint, and it could be cheaper in the long run).