updated 8/7/2006 8:24:22 PM ET 2006-08-08T00:24:22

The North Slope oil pipelines being shut down because of corrosion were clogged for years by sludge buildup that may have prevented the most sophisticated internal corrosion tests, officials said Monday.

The last time the pipelines were cleaned and tested, using a "smart pig" — a device pushed through the pipe to detect structural problems — was in 1992, according to federal regulators and congressional investigators.

Investigators have been told that the Alaska pipeline, which sends oil from the feeder lines to the port of Valdez, conducts operations to clean line sludge every two weeks.

In Anchorage, BP Alaska President Steve Marshall said the company believed that ultrasound tests were an adequate substitute and that the "smart pig" tests weren't necessary. He acknowledged in hindsight that was not sufficient.

After a major spill on one of BP's three North Slope feeder lines last March, federal officials became concerned about inadequate testing and possibly a wider corrosion problem and ordered the company to conduct a "smart pig" test within three months.

But the company said it could not meet the deadline in part because it was responding to a federal grand jury investigation into the March spill and that "it was working to determine the volume of solids likely to be encountered" in the lines, according to federal officials.

In mid-June, Rep. John Dingell, D-Mich., pressed the federal Pipeline and Hazardous Materials Safety Administration on why the required pig tests were not being conducted.

Three weeks later, the agency's chief, Thomas Barrett, and two senior officials traveled to the North Slope.

"We came away with significant concern about BP's progress" in dealing with the sediment that had built up in the pipelines and were hinder the testing, Barrett recently wrote Dingell.

"The presence of significant volumes of sediment and sludge in the lines poses a risk of further corrosion and interferes with internal inspection operations that are useful in detecting pipe anomalies," Barrett continued.

Then, BP Alaska officials came up with new estimates that lowered the amount of sludge believed in the lines, and told federal officials the material no longer prevents pigging the lines. BP had tried to use the pig tests in 1999 but did not complete the process, according to Dingell's investigators.

Last May there was believed to be up to a foot of sludge in some parts of the 30-inch diameter lines.

"It is appalling that BP let this critical pipeline deteriorate to the point that a major production shutdown is necessary," Dingell, the ranking Democrat on the Energy and Commerce Committee, said Monday

Bill Hedges, BP's technical expert on corrosion, said in Anchorage on Monday that the company has an extensive anticorrosion program that relied heavily on ultrasound technology.

Thousands of points on the 22-mile pipeline system are checked annually. "My assumption is that we didn't do it in the right spots," Hedges told reporters.

The company announced it was replacing 16 miles of the transit system — two of the three lines — and preventing 400,000 barrels of oil a day from moving out of the Prudhoe Bay fields.

"We've learned ... that BP had not cleaned many of its pipelines for years. In contrast, other pipelines up on the North Slope are cleaned every two weeks," said Rep. Ed Markey, D-Mass., a member of the Energy and Commerce Committee.

At a House hearing last April, Stacey Gerard, chief safety officer at PHMSA, the federal pipeline regulator, said he could not say why BP Alaska did not use "this basic technique" of running a scraper pig through the lines to regularly remove sludge which he said is known to be hazardous to the pipelines.

"Is it just basic incompetence on their part?" asked Markey.

"We have no single logical reason why they did not use the scraper pigs," Gerard replied.

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