Some 20 years later, oil from the Exxon Valdez remains trapped in the beaches of Alaska's Prince William Sound. A three-year study by Temple Civil and Environmental Engineering Chair Michel Boufadel has determined that low concentrations of oxygen and nutrients are hindering micro-organisms from biodegrading the oil. "The oil could be maybe one foot below the beach surface and in contact with sea water with a lot of oxygen, but the oxygen doesn't get to it," Boufadel said.