State officials said they are reassured that BP is on top of its North Slope pipeline integrity and safety inspection and maintenance program following meetings with the company Nov 8.
Concerns were raised after an internal company data base showing numerous "F" rankings on field pipelines indicating significant corrosion was leaked and published by ProPublica, an investigative journal.
The reports attracted wide attention because of BP's recent accident with the Deepwater Horizon rig in the Gulf of Mexico and the resulting large oil spill.
BP employees told ProPublica that there has been 80 percent loss of pipe wall thickness at many of the segments receiving an F ranking, according to the published report.
"The published reports concerned us, but BP walked us through their process and assured us that the system is receiving the necessary oversight, and that corrective actions are being taken when needed," Allison Iverson, director of the state's Petroleum Safety and Integrity Office, said in an interview.
The data that was reported on is used internally by BP to track inspection results and segments of the field pipeline system where remedial work is needed.
Iverson said the F ranking does not mean the pipeline is unsafe or operating beyond limits set in state and federal rules, but that corrosion has been detected and work is needed.
"There has not been a failure of a pipeline at any of the points indicated by an F ranking," Iverson said.
BP has maintained the tracking system from the 1990s. Iverson said she was interested to learn that the number of F rankings, or points needing action, has not changed significantly since 2002 although BP has sharply increased its pipeline inspections since 2006, when corrosion in Prudhoe Bay field pipelines caused oil spills.
BP is doing more than 200,000 inspections this year, the company has said.
Data in the system is updated as new inspection results are inserted and repairs are completed, and the overall status is constantly changing, Iverson said.
Of 151 F-rankings shown in the data, as of Nov. 3, BP had 15 pipeline sections shut down for repairs, 17 segments that have been D-rated, or operated at lower pressures, and 104 sections where corrosion has been found and repairs scheduled but the pipeline section can be operated safely, Iverson said.
In the data set that had been leaked, there were 15 segments where repairs were completed but the data had not been entered into the system, she said.
"We were reassured, but it doesn't mean we won't be following up with BP to monitor their progress. We did have some questions they still need to answer, one being how they show a D-rated pipeline in the data base so the operators know that the pipeline cannot be operated at normal pressure," Iverson said.
BP spokesman Steve Rinehart said the company manages about 1,600 miles of field pipelines on the North Slope.
"We do not have any F-ranked pipelines. We do have 61 pipelines with specific identified sites where corrosion or other damage gets an F-rank," Rinehart said in a written statement.
"An F-ranking does not mean an unsafe condition or imminent failure. It does prompt a higher-priority repair plan depending on technical details and engineering review. The result can be immediate action -- a repair, reduction in allowable operating pressure, or removing the pipeline from service -- or a longer-term response."
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