When I bought my house I saw some unexplained pipes in the wall. The owners said that the house was heated by natural gas, they had never used oil. The inspector made no mention of the potential that there might have been an underground tank. I wasn’t taking any chances. I called a tank investigation company.
Under the Navigation Law of New York, the owner is absolutely and unconditionally responsible for oil contamination. In fact, the Department of Environmental Protection is entitled to clean up the site and bill the owner for the costs associated with cleanup.
Luckily, the tank inspection company found the tank (1000) gallons, and we refused to close unless the Sellers cleaned up, which they did at a cost of more than $30,000 (often not covered by home owners insurance). That would not have been a happy day for a new home owner. I learned my lesson, and I try to impart that knowledge to my clients.