Hi all,
As one of the original diggers I'd like to add to this topic as it's cropped up.
It seems likely that the main sump is fed from the surface stream going down to meet it at a point further on. So draining the sump only seems likely when the surface stream is dry, i.e. late summer.
Just back from the main sump is the other perched sump. It could be possible to drain that sump into the main sump as it's a little higher. This would hopefully overspill some place downstream and not raise the main sump level.
Some of the main sump water could then be pumped back into the higher, now empty perched sump. Whether this would lower the main sump enough to pass is debatable though. The outlet of the perched sump could also be blocked up with concrete, and this would give it more capacity which would help.
Another possibly we considered is to pump the water up to Huge Crawl (just off the bottom of the ladder) We don't know where it goes, and it may just create a circular flow, but if Huge crawl were to bypass the main sump it may allow emptying that way. It would mean pumping water up maybe 40m or so though which is no mean feat.
There must be a dry route somehow though, as the cave always draughts... The main draughts underground we saw were in the choke above Room 101, that draughts like mad. But a big looks frightening upward boulder choke
The obvious thing though for the cave, would be to divert the surface water to the "dry entrance" and start a surface dig in the normally wet entrance (if that makes sense). Chances are good that that would open up a whole parallel route down into the cave, as the water isnt seen again in the normal cave.
Would need permission from Oakover estates and would generate a lot of rock I think. But solid rocka may not be far away.