Well, in Tawas MI, at my mom's house, there was a flower bed in the front yard, the whole left side of the house that had the same problem. The soil is all sand, so we thought that any chemicals would have washed away. About 10 years after she moved there, I put down sections of newspaper with many bags of top soil over it, and planted iris--2 weeks later they were all dead, and the ones I planted in the back grew fine. So here it is 30 YEARS later and still nothing will grow there--not even the invading grass. You will need to get it tested, and not just a regular test either ---$$$. contact your extension office. oh, by the way, good luck!!

Actually I was just reading not too long ago about experiments using trees to clean up this sort of thing. I did a quick google search and had a lot of hits:
http://www.google.com/search?hl=en&q=using+tree+to+remediate+petroleum

The idea is to plant one of these fast growing trees which draw the contaminants up from the soil. You'll have to chop down the tree, but at least you'll have something growing there.