Why I choose elevation = 270 msl.? Because if we go down more than elevation = 270 msl. it too hard to come back for improve the operation for closed to creek 20 m.
But in case of we can not find the solution I will come back and decrease the operation again.
Please remind , this data from block model update by Anne-sophie Castex in April 2015. (Block model just guide us where we will go and where the potential of our deposit but not 100% of correction.)