Hi
Regarding the drainage tunnel, the original information came to me from Eric Ffoulkes - though its exact origin he didn't say. Boyd has even less to say.
Not much help, I'm afraid.
I do suspect that 1851-1965 might be a long stretch for one man - did you mean 1851-1865 by any chance ?;)
Kind regards
Graham
The map is the territory - especially in chain scale.