At what depths and grades does it begin to make sense to consider underground mining? If the boys find the root what grade/size does it need to be? Also how far away from the open pit operation would it have to be to not be impacted by past (or present depending on lifr cycle) blasting activities at the pit. (I assume there would be fracturing radiating beyond the pit, but I am a forestry guy not a geotech)

Thanks in advance

B