It turns out the house is pretty close to dead center in an area known as the Koppers Superfund Site, an area of serious soil contamination.

You, the unit owner own the plumbing that's inside your unit (not in between the walls/floor/ceiling) such as the A/C drip pan, leaks from the actual washer (not the drain pipe within the wall), the plumbing underneath your sinks within the cabinets, etc. 

Also you might consult a soil or structural engineer they typically will not come out without charging you but you will have a professionals view point of the problem and the costs involved.

Some of the more patient scammers will even do a couple of good jobs or a few months of good work to earn your trust, only so they can rip the carpet out from underneath you.I have lost well over 100K giving money to contractors who earned my trust and friendship as part of a grander scheme to blatantly steal as much as they could. 

@AJ ArdA Phase 1 study won't look for things like asbestos or lead paint unless it's specifically requested, these studies are looking specifically for soil and water contamination, issues with the structure are outside the normal scope.  

Will  this involve getting a soil report from a licensed soils engineer so the architect and engineer know what type of foundation they will have to design and the owner have built for the building?

You can watch people testing water and soil around Tokyo with dosimeters.

Its coming from underneath the house, maybe pipes have burst I'm not completely sure.

Remove the sizing with hot, soapy water and you'll leave the surface ready to be lightly sanded then painted.When it's done wrong it bonds directly to the surface underneath and you're going to destroy that surface trying to remove it.On my first major fix-up, I totaled three walls trying to remove wallpaper and spent over two months removing borders in multiple rooms.

Business, building, and the land underneath it?