There are many postage stamp-size lots, irregular, unbuildable, brownfield (contaminated) property, etc. 

What is the process if removed a underground oil tank and the soil is contaminated?

I will point out that on a small build it may not be worth that money because the "test" they do is not a soil sample or boring of the land, it is a research into the property to determine if a laundry facility or auto body shop or some contaminate / polluting type of business or entity was once on that lot a long time ago.

This soil contamination is not likely to be covered by insurance. 

The main problem is if there is a leak and soil is contaminated.

I came across an REO with disclosed soil contamination.  

With raw land, there are only a few questions that you can askSize of land, zoning, any known contamination?

. - Leave untouched as much of the remaining land as possible - both for a greater feeling of privacy and exclusivity for the resort guests and owners, as well as for environmentally responsible development.Pulling all of the expense figures out of thin air, I would pay 125mil for the property.The main concern for due diligence would be environmental contamination from previous activity - both military and research facilities.

Also if the property is older there could be asbestos or other contaminants and then demo can be more expensive because of additional regulations required.  

@Ryan McCoywhat kind of contamination is it listed as super-fund site?