I'd get your local Building Inspector out there pronto! Find out if the setback is enough, some places it's 25'. Ask if you will ever be able to build a deck there. Is the first footing going to be in the crawl space? I'd have them demo it out of there. Not your mistake to live with, especially if you need to dig some deck footings or garden structure. Structurally, ask the inspector when he comes for your courtesy call. I sure wouldn't let them leave any of it in my yard. He who hold the money....
Be safe, G