Were interested in buying a old country store whose gas tanks have been shut down due to the new double tank standards and the tanks are still in the ground... do we need to get a environmental phase 1` done and if so what is the cost and what does it consist of?

How much are the current owners paying you to take it? A few years ago, my daughter was doing her environmental engineering coop with an oil company.
They were pulling all their old tanks. I don't have figures on it, but likely it exceeds the value ot the property otherwise. The soil around the tank must be checked, and excavated to uncontaminated ground. The contaminated soil must go to a secure landfill. You may also have to obtain permission from adjacent property owners for test borings on their property. Bad deal. Try to find a contractor that does that work and ask for an estimate.

Remember this the next time a fillup leaves your wallet empty. I don't know if all this is reducing water pollution, but it is enriching contractors, and guess who pays in the end.