Is it near a river? What about ground water level? Sometimes that has to be actively pumped out/up. Also large water mains may fracture, and soak it. Blub Edi

Is it near a river? What about ground water level? Sometimes that has to be actively pumped out/up. Also large water mains may fracture, and soak it. Blub Edit: This can be seen often during the early stages of larger building construction, when they 'dig out' the hole for the basement, and optionally parking spaces below that, like in your case. There are large pumps, always working, 24/7 pumping it elsewhere. Those don't vanish. They are just being replaced by permanent installations integrated into the building, or near to it. Similar things apply to many subway tunnels. Not always. Depends on the location of course.