Sounds like time to build an ark, but joking aside ground water don’t always go to the bottom of the hill, my brother in law Wes a driller and soil sampler he tested the ground before building commenced and I remember a few occasions were he has hit water on high ground there is a golf course near me that’s way above any low lying land pretty elevated but a couple of meters down he hit what must have been an underwater lake the gusher was immense, you can have a solid crust of a meter or two with water underneath so the builders may have breached the crust, most of portishead is built on a cr