[claytonx]

I should have thought the water could be seeping through from the reservoir above, possibly going through strata that would colour the water and Utilities having to filter it before allowing it to go into local streams. If it was a drift mine there is no need for a Audit or any other tunnel, as you would only need them in a mine with a shaft. The coal would be taken out at the top of the shaft and materials ie props, girders, timber taken through the Audit, tunnel about 20 ft lower down the shaft, we call it the material level.