We had this email today from the author of mining history.
Hi Andy
Here are the relevant documents.
A word of warning; I nearly died in the cave in 1969-70, I got stuck and no
one knew where I was, the one time I did not tell anyone I was going.
The other risks and hazards are roof falls, large pieces of shale, or
lamprophyre falling on explorers - hard hat essential.
Face & eye protection masks - there are some nasty fungal spores in the air
and they give some people serious lung problems (Aspergillus fungus in
particular). A lot of broken glass in the floor debris - so again risk of
nasty cuts if you trip up.
The lower levels of the cave are usually flooded; when I got in trouble was
after a long drought and the lower levels became accessible. I went down not
realising how dangerous these were. I was used to exploring caves and mine
workings - but it caught me out.
The local farmer is usually amenable to visits if you ask him. If you do not
ask his permission and he sees torchlight or hears noise he usually calls
the police.
This mine is about 200 years old, although it constructed in the "pillar and
stall" mining method - which is strong at supporting large mining voids. It
is old for "pillar and stall", most coal mines have collapsed with this
technique as have some of the limestone mines. The area suffers occasional
earth tremors, and this definitely weakens the pillars. This mining method
is safest when 65% extraction was the maximum, leaving 35% unmined rock to
support the stalls. There are places in the mine where this value is nearer
85% extraction, 15% left as pillars. I fully expect the mine to collapse
further, and each time a pillar fails the stresses in the stall roof change,
thus increasing the risk of a catastrophic collapse. There are signs of that
about 400 m to the NW of mine - a large crown hole exists in the woodland.
I feel it is my legal duty to warn you of these things as a professional
mining engineer and geologist.
Regards
Alan