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

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. 

@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.  

If being environmentally conscious isn't a concern and a 20-30 year lifespan is acceptable they will do fine.

Look into ESA phase II analysis (aka Environmental Site Assessment) for soils.

A few months ago, at the Environmental Information Association convention in San Diego, we met a man from Home Depot looking for consultants to help with asbestos, mold, and lead.  

You’ll also want to think about getting a Phase I Environmental Site Assessment, in case of any undisclosed environmental hazards.Below are a couple of websites to get you started in your research.https://www.epa.gov/enviro/sems-searchhttps://www.abandonedmines.gov/about_coal_mines#:~:text=There%20are%20nearly%205%2C200%20coal,environmental%20and%20non%2Dcoal%20problems.https://www.abandonedmines.gov/report-a-mine (for a list of state agencies)https://www2.illinois.gov/dnr/mines/AML/Pages/AMLProgram.aspx (only beacuse i'm guess that the property is in IL)

There is a Pilot gas station about 120 ft (slight up gradient) from our property, and our environmental phase 1 shows there was a spill in 2011.

@Jordan BerryDo you know if you will have any environmental issues with the property having a laundramat on the site?