I personally would not even remotely consider purchasing a home site that could be subject to a any significant pollution. Why? The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) holds strict liability with regards to clean up. Consult with a well qualified attorney (who understands environmental liability). If you buy this property you could be committing to clean up costs even if you sell it later. It becomes an in perpetuity circumstance of liability. If contamination is found on your site you may not be liable for clean up costs, as the gas station owners (all of them-even previous owners) would be required to assist in costs, but this would potentially cost you in legal fees not to mention the added headache. I recommend extreme caution with this action.
CERCLA Overview | Superfund | US EPA
Consider the following:
You buy pollution insurance.
Implications: you would be required to disclose to future buyers (depending upon your state real estate laws for disclosure)
They could discover this by requesting a CLUE report or having an insurance agent research the property.
I am not saying to not buy pollution insurance or not, just making you aware that this could be used against you in the future if you sell the property and failed to disclose a potential material defect (consult a well qualified real estate attorney on that point).