Dauphin Island Sea Lab classrooms were evacuated, and a half dozen people visited the town's doctor apparently after exposure to hydrogen sulfide, a poisonous and foul-smelling gas that occurs naturally underground with highly sought methane.
"It appears to have been a complete breakdown in this fail-safe system we thought we had here on the Island." - Bill Harper, president of the Dauphin Island Property Owners' Association
ExxonMobil officials said the noxious gay may have been released during a brief incident at the company's Mobile Bay 76 facility, the double-platform that serves as the hub of the company's Alabama gas harvesting operations. The company's problems began with dropping pressure in a line from the main-land that provides clean, processed gas to the platform, said Paul Dieffenthaller, chief of ExxonMobil's operations in Mobile Bay.
As operators later discovered, "there was trash in the fuel gas line," Dieffenthaller said. The line is used to feed and ever-burning flare in the emergency vent high above the western end of the platform as well as the platform's power generators, Dieffenthaller said. The pressure continued to drop, and that may have extinguished the flare, he said.
At the same time, the platform's highly automated system temporarily shut down operations - perhaps another result of the dripping fuel line pressure, Dieffenthaller said.
Ordinarily, when operations shut down and the entire system "de-pressurizes," any deadly hydrogen sulfide in the gas escaping through the vent is burned, or "flared," and converted to sulfur dioxide, another toxic gas more quickly dispersed by the nearly constant sea breeze.
But on Tuesday, the flare was out for approximately eight minutes, and the gas was not burned but escaped into the atmosphere unadulterated, he said. ExxonMobil is conducting an official investigation into the incident's cause, he said.
The facility's sensors detected no escape of hydrogen sulfide, Dieffenthaller said. However, the flare is located on the western end of the facility and the prevailing winds run westward, so on hydrogen sulfide escape might have been undetected, he said.
The rotten-egg odor rolled westward from the island' east to the island's middle before dissipating, according to witnesses. "The building sucked it all in, so by the time it cleared up outside, the smell was unbearable inside and classrooms were evacuated," said George Crozier, director of the Dauphin Island Sea Lab.
Crozier said dozens of people, including housekeeping staff, faculty and students, complained of sore throats, itchy eyes and nausea - all symptoms of hydrogen sulfide exposure. Workers at Town Hall, at the island's middle, said the smell nearly over-whelmed them.
Dr. David Jenkins, the only practicing physician on the island, said he'd seen a half dozen patients reporting symptoms "that could be consistent with hydrogen sulfide exposure." The symptoms were minor, and all patients were evaluated and released, he said.
Ralph Hellmich, south Alabama operations supervisor for the State Oil and Gas Board of Alabama, said he was aware of no similar incident occurring since the board was established in 1988.
For those familiar with the Mobile County EMA's recommended response to such a danger, a warning of such a leak would mean closing up their homes and businesses and turning off air conditioners and closing vents. But no warning came.
"It appears to have been a complete breakdown in this fail-safe system we thought we had here on the island," said Bill Harper, president of the Dauphin Island Property Owners' Association.
A message left with Mobile County Emergency Management Agency was not returned Tuesday afternoon.