what can i do when our local prosecutor commits fraud

Unfortunately, there aren't enough facts given here.   What role do you play in this matter?  Council Member?  Concerned citizen?  Subcontractor or supplier?   What is your goal here: Punish the prosecutor?  Make sure the project is properly completed?  Something else? If the prosecutor is allowing a draw, this is obviously a public project, but what isn't clear is what the remaining damage is on the project.  Since you went to the US EPA, it sounds like it is an environmental issue.   Once the project has reached substantial completion (a term of art meaning that the project is fit for its intended purpose, but there still may need to be some final punch list items completed/repaired) a significant amount of the contract balance should be released.  Is the "last pay" the release of retainage or the last interim draw?  The project may not be accepted as final and complete.  The public authority may have "settled" with the contractor or its surety and paid them out final with a deduction for the remaining work to be completed which they may be planning to do with another contractor or merely accept as is--unless it violates another law or regulation. If you can let me know more of the facts I may be able to give you a better answer.