Maury Island has the gravel Sea-Tac’s runway needs. It also has arsenic-laden soil, a vulnerable aquifer, and some very worried islanders. By Eric Scigliano • October 9, 2006 12:00 am IF THIS STORY HAD APPEAREDtwo weeks ago, you might have thought it an April Fool’s hoax. Consider: A Japanese-owned sand-and-gravel company plans (in stages) to strip-mine 235