Hi People
I have been fortunate enough to obtain original plans of Richard Thomas and Baldwins who worked the mine until closure. They show the water level at 03-03-1966, so clearly pumping had ceased, this convinces me that they are the abandonment plans.
These have great detail and show two now submerged pump houses as well as properly drawn surface features.
I will be getting them digitalised and eventually uploaded to the NAL website.