It is a question we’ve been asking since BP's "Deep Clean" began last October. Now the city of Orange Beach maybe a step closer to answering that question.   For months now we've watched as sand is dug up from the beaches, sifted and replaced in an effort to deep clean oil from April's BP oil spill. "We've been interested in the impacts of beach systems since the oil spill," says Auburn civil engineering professor Joel Hayworth. "We've been looking at various aspects of those impacts from a research standpoint." Hayworth is in Baldwin County to start gathering…