@Jon Klaus, there's a huge difference between simple environmentally sensitive portions of a parcel, and hillside lots in the coastal areas, where we have earthquakes!

Things that used to be called "drainage" or "swamp land" now can be deemed homes to fairy shriimp, or listed as environmentally sensitive, and "wetlands".

However some lawsuits (like environmental issues) still can target the owners (for deeper pocket).

To be more successful, you simply have to work on the other elements to progress your REI pursuit.

If the contractor told him 70k, and he doesn't mention to us anything about mold, lead or asbestos yet he still gives us a list of repairs to be made them I'm thinking it's pretty safe to assume that none of those repairs include the aforementioned environmental issues you're now asking about. 

Until you have all the elements necessary for a complete loan application, these disclosures are meaningless in light of the new TRID requirements which went into effect on October 3, 2015.  

...The "surprises" are a necessary element for TV, otherwise there would be no drama. 

@Daniel Moctezuma, I don't have any direct experience but the problem that I see is if the tank leaked you may have an environmental clean up on your hands (need to clean up the soil as well) - it may not be as "simple" as only removing the tank. 

Environmental moisture vapor, within the air or being released from the ground, can easily collect on the underside of flooring.  

But the NIMBY'ism and the anti-growth element is a much bigger deal.