Elstree South station

I work on the site of what would have been the Aldenham depot of the Northern line. I find it quite easy to picture how the depot and adjacent stations would have looked and never really get past the paradox of how "convenient" it would have been to have Elstree South station on the doorstep given that had it indeed been built then I would not have been working where I do. My company kindly lay on a minicab to Stanmore or Edgware otherwise I'd have to suffer the 107 bus which is fine in the mornings but a 'mare of an evening.
My question relates to how the streams and waterways that still run in the area, and were marked on the plans ( cf. By tube beyond Edgware ), would have affected the building of both the depot and Elstree South station. Would these have been buried in pipes, I suppose like at Sloane Square, or diverted some other way. These days at the Elstree Hill exit of the petrol station there is a sump that trickles water into the road, summer and winter, and seems to me to be roughly where a pond was marked on the plans mentioned above. Clearly this has been caused by human intervention so would other "interventions" have resulted in wet areas in the depot and station. Can a station be guaranteed watertight?
I'd welcome any thoughts.