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A section of the BP pipeline that leaked thousands of gallons of methanol and oily wastewater into the Alaskan tundra on Saturday was flagged by the company more than a year ago as so corroded it presented an imminent threat of rupture.

Documents obtained by ProPublica last fall listed 148 sections of pipelines that BP said failed its basic inspection criteria. These sections had worn so thin – in some cases to a few thousandths of an inch – that internal BP records said they needed to be replaced, or operated only under reduced pressure. Among the pipelines listed was the one that leaked Saturday: the “Drill Site L1” line at the company’s Lisburne Production Center, a large oil gathering facility near the shoreline of the Beaufort Sea.

The spill is the latest in a string of accidents at the Lisburne center and BP’s other Alaska facilities that, combined with last year’s accident in the Gulf of Mexico, have weighed on the company’s reputation. The latest spill is a setback for BP’s new CEO, Robert Dudley, who promised to make BP’s global operations safer and more reliable after the Deepwater Horizon disaster last spring.

ProPublica wrote then that while attention was focused on the Gulf, BP’s Alaska oilfields were deteriorating and presented grave safety and environmental risks. For more than a decade, BP’s maintenance of key facilities there had lagged. As the company cut costs, it reduced its use of chemicals and monitoring meant to control pipeline corrosion. It allowed aging pipe valves, large turbines and fire detection systems to age without regular maintenance, according to a series of internal BP documents and reports obtained by ProPublica.

BP’s pipes and equipment on Alaska’s North Slope – despite nearly $200 million a year in maintenance expenditures – were degrading more quickly than they could be repaired, mechanics said.

"We found that 50 percent of everything that was originally brought up was not fixed, it was ignored," Marc Kovac, a BP mechanic and PACE union representative on the North Slope, told ProPublica in an interview last year. "BP plays the time game. People forget and they know that. So as long as they file reports and do investigations and produce paperwork, they know that people will eventually go on with their business."

Then, last year, BP started cutting back again. From our earlier report:

… even before the enormous costs of the Gulf spill created an estimated $30 billion in BP liabilities, the company was eking out more “efficiencies” in its Alaska budget. It said it would maintain record high funding for new projects and major repairs while reducing its budget for regular maintenance, according to a letter that BP Alaska President John Minge sent to Congress in February 2010. The letter said holding-tank inspections will be deferred and replacement of one pipeline will be postponed; flows through that line will be reduced "to mitigate erosion."

The Lisburne facility, which a ProPublica investigation showed has experienced repeated accidents and spills, processes some 30,000 barrels of oil a day but has been shut down since June for maintenance. The leak was discovered as the pipeline was being tested, according to news reports.

Neither BP nor the Alaska Department of Environmental Conservation immediately responded to requests for comment. We'll update when they respond.

Staff reporter Nick Kusnetz contributed to this report.