I am not sure where the valve and dam is somewhere in the old north east level I believe, long abandoned. These would all have all been built by the old men of 1842 onwards.
Dams, valve and standages are all common in mines although I am not sure what this particular dam was for. They are mostly used to divert water or for pumps to pick up.
Blenkinsopp is not really a wet pit, pumping about 5-6 million gallons a week (I think, and varies from winter to summer. I will recheck this).
Wet weather makes a difference as the pit is not that deep compared to other mines so rainwater quickly finds it way in (usually 2-3 days).
The real problem with the water is the acid content. Some pump parts were lasting no more than a week and several hauler ropes snapped because of it. Some parts of the mine are more acidic than others, this could be because of nearby Byron water seeping through.
All the mine water is pumped to a standage at the top of 3rd South by Mono and Flyght pumps and from there is picked up by Mackly pumps with one submersible.
It is then pumped up to the shaft where another sub pump, pumps it up mallburn shaft and into lagoons. It is then treated with burnt lime to neutralize it before going to a nearby stream, the Tipalt.
Another local pit, Bardon Mill, which also worked the Little Limestone seam, was extremely wet and was pumping nearly 2 million gallons a day. It too was not very deep and is said that you could hear the trains running on the Newcastle to Carlisle railway and also boulders being dragged along the bottom of the river Tyne when it was in flood. The people in the local houses could clearly hear when the faces were being fired !!