When the oil tanker Exxon Valdez collided with a reef in Alaska's Prince William Sound in 1989, scientists believed that the oil would eventually disperse, but today large quantities are still found underneath the gravel beaches. "Talking to people who were involved in the original response, what was on the surface was viewed as what was representative of what was happening in the subsurface," said Temple environmental engineer Michel Boufadel, who has studied why the oil remains. "So there was a lot of focus on getting rid of the oil that was apparent on the beach surface."