I saw something somewhere recently that on shaft mines, it is a (I guess recent) practice to refill the shafts with a tailings/concrete slurry after it has been defined that the shaft is "exhuasted".
Don't recalll where I came across that info. Hell, I may have even dreamed it, who knows.
In todays lawsuit happy society it makes sense though. Plug the shaft and no one can sue you for falling into and/or getting lost in it.
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