Michel Boufadel began a recent presentation about Marcellus Shale drilling with a photo of the ruptured Exxon Valdez oil tanker spilling into Alaskan waters, a disaster whose remnants the Temple civil and environmental engineering professor has been studying for years. Many people assumed that the oil from that 1992 spill had been properly remediated and "was going to disappear," he said. "Yet it is still there. That is the problem with groundwater pollution. It doesn't go away that fast." Boufadel argues that there should more risk assessment studies on the impact of Marcellus Shale drilling. "There shouldn't only be one study," he said. "There should be 10 or 20 studies."