When discussing this furher we need to remember that Cobb was an expert witness for the defence at the trial of the mine manager and mine company. Most of what he wrote was high quality factual detail.
It was part of his job to float possible explanations that the 1984 workings might, just by incredible chance, have filled with water a few hours before the blast that caused the breach. Put yourself in the place of the jury. Would you be able to say beyond reasonable doubt that such an event did not occur? I don't think so - although personally I don't find his arguments for this sudden flooding very convincing, but they are not completely implausible. He is just putting the case for what might have occurred, introducing doubt is part of his job
For what it is worth I thought about what the jury would have done if the mine manager's evidence had instead been along the lines of "I looked at the flooded 1984 workings and found no more water than usual ponded there. I thought it safe to proceed with cautious advance drilling". I don't think he would have been convicted without further evidence.
Incidentally, the "Like a tap turned half on" of water coming out of an earlier advance drill hole should not be interpreted as evidence that the 1984 workings were not flooded at that time. There is no suggestion that the hole reached the 1984 workings. If you are drilling a few metres in front of you, holing through into a void will be immediately noticeable. That hole terminated in coal/rock and was just a warning that some water was around.
In answer to Tom Ferry's point about the weather before the accident, Cobb did consider this. He said "The rainfall the day before the incident was only 0.4mm. It is highly unlikely that the inflow from rainfall would have been high enough to cause the flood.".
Sometimes we have to accept that full evidence will never be available.
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