Be really careful, there is too much liability associated with i

Your state should have a department of environmental quality (or environemnatl protection).  You need get answers from them.  Do not take word from the remdiation contractors, beacuse those guys are lower level field tachnicians, the raelly don't know.

Bottomline, you must understand what you are getting into, and the laws regarding UST (undergrand storage tank) varys tremendously from state to state.  So get a local professional to help you.