It has been two decades since the Exxon Valdez ran aground in Alaska’s Prince William Sound, spilling 11 million gallons of crude oil and making it one of the largest environmental disasters in history. Twenty years after the accident, its effects are still being felt by the wildlife, on the beaches, and among the residents — long after experts predicted the oil would be cleaned up or dissipate naturally.

Funded by a $1.2 million grant received in 2007 from the Exxon Valdez Oil Spill Trustee Council, Temple University Civil and Environmental Engineering Chair Michel Boufadel has spent the past two years researching why oil from the Exxon Valdez can still be found along many of the beaches in Alaska's Prince William Sound. It is the first such study to examine the spill’s impact on the beaches and why oil still lingers.

“In 1994, there was a decision made to stop all remediation efforts on the beaches of Prince William Sound,” said Boufadel, a hydrologist who is an expert in oil spills and oil remediation. “That decision was based on the rate of oil disappearance during the first four years after the spill.”

Boufadel said that at that time, the oil was disappearing at a rate of about 70 percent and calculations showed the oil would be gone within the next few years. “The focus since 1994 has been on what is called the injury to the environment, how the herring are affected, how the salmon are affected.”

But five or six years ago, Boufadel said, there came an awareness that the oil was not disappearing at a critical rate, that it had in fact slipped to a disappearance rate of around 4 percent a year.

Over the past two summers, Boufadel and several Temple environmental engineering students have spent 30 days in Alaska, visiting six beaches in the Sound and collecting oil and sediment samples, as well as placing sensors to take year-round water temperature, water salinity and water pressure readings.

“Our goal was to try to understand what factors are causing the oil to persist in certain sediments along these beaches,” he said. “If the oil had only been found in one particular beach, then we would know the oil reached that specific location and remained there. In reality, within the beaches that we examined, you can find oil in one location on the beach, then you move 10 feet to the left or right of that spot and you will not find any oil at all.”

In his Temple lab, Boufadel has some 50 pounds of sediment and soil samples from the six beaches that contain toxic material from the Exxon Valdez spill. He has focused his study mainly on the geology and hydrology of these impacted areas as potential reasons why oil from the Exxon Valdez still remains in the beaches of the Sound.

“We think there are hydrologic factors that are preventing the oil from degrading naturally,” he said. “We discovered on one beach that whenever you have fresh water flowing seaward from the area behind the beach you don’t find much oil.”

Boufadel hopes to issue more definitive conclusions later this spring or early this summer, as well as provide guidelines for locating the oil within the beaches and how to clean it up. As part of his ongoing study, he will be leading another field research visit this coming summer in which he will explore remediation techniques on two of the six beaches.

“As engineers, our goal is not only to understand the factors causing the problem, but also to provide solutions,” said Boufadel.