I had a magnetometry survey (fancy name for an oil tank sweep) conducted at a property I am looking to purchase in Northern New Jersey. The scan detected an anomaly between the grass and driveway. While a metallic footprint consistent with a large metallic object present, the absence of a fill pipe or vent pipe necessitates the need to excavate the area with shovels. The seller is Fannie Mae and the seller's is not allowing to dig to find out whether its an oil tank or not. Also present is one Oil line in the basement that leads to the general area of the anomaly (apparently there should be two lines but only one is present). No other anomalies on the property exist. Last time the property was sold was in 2004. The town does not have any records of permits for the removal of an underground storage tank. Property has been in foreclosure since 2014. 

The cost to remove an oil tank is ~$2,500 (quoted by the same environmental company that did the inspection above). The issue is to confirm if the soil is contaminated and the extent of the soil contamination. The seller is not allowing to dig the area. The property has probably $30,000 - $40,000 of in the money equity in its current condition. 

Question to the more experience investors is whether I should do the deal or not? Also, is there any other way to find out if there is an oil tank or not? I discussed the possibility of a non-invasive scan but the environmental company suggests that's not going to help us here. The non invasive scan is only going to tell us that there is an anomaly there (which we already know) but not tell us why there is an anomaly and what really is there (septic, oil or dry well). 

Any help will be much appreciated. I clearly understand no one will be providing legal advice. But if you folks were in my shoes, what would you do? 

Thanks