ANCHORAGE — Oil resumed flowing through the trans-Alaska pipeline Wednesday, but at only two-thirds the rate before a 31/2-day shutdown caused by a leak.
The shutdown turned out to be the second-longest in the history of the line that transports about 13 percent of the nation’s domestically produced oil.
By Wednesday morning, the pipeline was moving crude from the nation’s largest oil field at a rate of about 400,000 barrels a day. Before Saturday morning’s shutdown, it was carrying about 630,000 barrels a day.
The 800-mile pipeline was restarted at 9:03 p.m. Tuesday despite the leak near a Prudhoe Bay pump station. Oil continues to seep into the basement of the booster pump building, the last stop before oil enters the main line for the trip to a Valdez marine terminal where oil is loaded onto tankers to the West Coast.
The amount of leaking oil worsened when the pipeline was restarted. More than 2,300 gallons of oil flowed into an 800-gallon containment tank between 8 p.m. Tuesday and 4 p.m. Wednesday, and vacuum trucks were continuously removing it, said Stefani Bell from Alyeska Pipeline Co. The amount is about half of what has leaked from the broken pipe so far.
Alyeska received approval from state and federal regulators to restart the pipeline even though a bypass pipe to circumvent the leak was days away from being installed. Officials wanted to restart the pipeline out of concerns that ice was forming in the line and wax from the oil was accumulating during the prolonged shutdown.
One of the main concerns was about a device called a cleaning pig that was in the line. If there was ice and wax in the line when it was restarted, the pig could push that material into machinery and damage it, likely causing another shutdown.
With oil again moving, the pig, which was about halfway down the line near Fairbanks, could be captured between two valves and removed.
Bell said there were no problems reported with the restart.
The 84-hour shutdown turned out to be the longest since Aug. 15, 1977, when the pipeline was shut down for four days, 14 hours and 11 minutes, a few months after it went into operation.
It appears the leak is from part of the booster pump’s discharge piping, either in the wall of the booster pump building or in an underground section outside the building.
Alyeska decided a bypass pipe would be the quickest fix because the damaged pipe is encased in concrete. Fabrication work on the 157-foot pipe was being done in Fairbanks, and it was expected to take at least several more days to finish the work. Then, the pipe will be flown to Prudhoe Bay, assembled and installed.