Roy I do not know how you obtained a copy of that plan, but you have reminded me of a possible source of Cumria Mine plans/ documents..
I carried out some research in the Cumbria record office, where they hold some of the Walton family documents.
It is fully of plans, and mine accounts. I have obviously spent some time looking at these and on one occasion the archivist, told me in confidence, that only part of the family documents were given to the office. Apparently some of the family wanted to retain them, so a compromise was made.- some kept and some given to the C.R.O.
This raises the possibility that somewhere in the county there is a large chest of interesting material!