Gas leak at North Slope oil development continues as ConocoPhillips says source remains unknown

The natural gas leak detected last week at a North Slope oil development has not yet been stopped, ConocoPhillips officials said Wednesday, and the company has not yet identified the source of the leak.

The company said Monday that they decided to evacuate non-essential employees from Alpine Central Facility and CD1 pad where the leak was detected. Approximately 300 personnel were relocated, ConocoPhillips spokesman Michael Walter said Wednesday. Typically, 400 employees are housed at the Alpine Central Facility, he said.

Essential workers remain at CD1, and the company continues to monitor the situation and investigate the cause of the leak, Walter said.

“Crews at Alpine and the Incident Management Team in Anchorage are currently working to identify the source of the natural gas,” Walter said. “That information will inform on how we move forward to mitigate the release.”

The Alaska Oil and Gas Conservation Commission is investigating the situation as well, but the agency will not have any further comment until the investigation is complete, said special assistant Grace Salazar.

“We have staff that are in contact with the operator,” she said.

Some residents of Nuiqsut, a village about 8 miles south of the development, continue to express concerns about the situation. Over 20 families had left the community as of Wednesday morning and seven were waiting for more information to make a decision, said Mayor Rosemary Ahtuangaruak.

The community, which has a population of about 500, isn’t in a forced evacuation status, but officials are evaluating the air quality in the village and are ready to ask residents to evacuate, Ahtuangaruak said.

Ahtuangaruak said that residents continue smelling gas in Nuiqsut.

Walter said that the odor is likely not coming from the leak. He said that the gas in the ground has “a very faint, slightly sweet organic odor only present in higher concentrations.”

The utility company for Nuiqsut, the Nuiqsut Utility Cooperative, adds a harmless chemical called mercaptan to natural gas. Mercaptan has a foul, rotten egg odor, to ensure natural gas does not go undetected if there is a leak.

During the leak, Nuiqsut’s biggest gas customers have temporarily switched to diesel fuel, and because it takes time to cut down on how much mercaptan is added to the supply, the gas being burned now has a larger concentration of mercaptan, a North Slope Borough official has said.