Self-evidently it cannot be moved, so the location of a new shaft must only be determined after the most exhaustive investigations. These include geology, surface features, topography and environmental constraints, and all possible future changes and contingencies.
Given the high cost of shaft sinking, it is a mine planning question as to whether the shaft should be sunk to the bottom of the ore reserve in one operation, or to an intermediate position in the first instance, and further deepened at a later date. The mine in the next two sketches has 10 years of shallow production and 10 years of deep production. It is quite normal to have lower confidence in deep reserves and higher confidence in shallow reserves. The sketches only show indicative costs. Factors to consider in this situation are sinking cost, interest rates and reserve confidence.
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