From adn.com/newsreader

An internal BP maintenance report on its North Slope oil field pipelines gives about 150 of them an "F-rank" for severe corrosion, Pro Publica reports. And unnamed employees say leak detectors are in such bad shape that at some facilities they are shut down nearly a third of the time.

According to BP oil workers, that means inspections have determined that more than 80 percent of the pipe wall is corroded and could rupture. Most of those lines carry toxic or flammable substances. Many of the metal walls of the F-ranked pipes are worn to within a few thousandths of an inch of bursting, according to the document, risking an explosion or spills.

BP oil workers also say that the company's fire- and gas-warning systems are unreliable, that the giant turbines that pump oil and gas through the system are aging, and that some oil and waste holding tanks are on the verge of collapse.

In an e-mail, BP Alaska spokesman Steve Rinehart said the company has "an aggressive and comprehensive pipeline inspection and maintenance program," which includes pouring millions of dollars into the system and regularly testing for safety, reliability and corrosion. He said that while an F-rank is serious it does not necessarily mean there is a current safety risk and that the company will immediately reduce the operating pressure in worrisome lines until it completes repairs.

Unnamed BP insiders told Pro Publica that at BP's current rate of maintenance funding, all the necessary repairs could take 20 years.