I was trying to close on a house and the appraiser from the bank took a picture of the fill port of the tank sticking up between the brick pavers in the back of the house.
It's absurb to think this is a serious environmental threat , however the government is involved so...
Worst case scenario is that the lender will want the tank removed. Better case scenario is that the lender will allow you to 1)pump the tank 2)backfill the tank in place with fill sand 3)test the surrounding soil
I had the tank pumped (must be properly documented, waste manifest), you can't pump it yourself and dump the oil. I ordered 7 tons of sand, cut the top of the tank open, and backfilled it myself. Lastly, you have to have a licensed engineer take soil samples, which is the most expensive part.
Pump and Dispose: $900
Cut tank and backfill: $150
Soil Samples: $1200
You need to determine the cost to pump and either backfill/remove the tank by getting some quotes, and then decide how you want to proceed from there.