The pipeline crack was thin. That could have delayed detecting the oil spill’s source

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Workers clean the contaminated beach in Newport Beach, Calif., after a major oil spill off the coast.

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Ringo H.W. Chiu/AP

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Workers walk by as dead marine life washed up after the oil spill.

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Ringo H.W. Chiu/AP

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People enjoy the beach in the background as workers clean the contaminated sand.

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Ringo H.W. Chiu/AP

People enjoy the beach in the background as workers clean the contaminated sand.

Ringo H.W. Chiu/AP

Questions remain about when the oil company knew it had a problem and delays in reporting the spill.

A foreign ship anchored in the waters off Huntington Beach reported to the Coast Guard that it saw a sheen longer than 2 miles just after 6 p.m. A satellite image shot by the European Space Agency indicated a likely oil slick in the area around 7 p.m. and was reported to the Coast Guard after 2 a.m. by the National Oceanic and Atmospheric Administration.

Federal pipeline safety regulators have put the time of the incident at 2:30 a.m. Saturday but say the company didn’t shut down the pipeline until 6:01 a.m. and didn’t report the leak to the Coast Guard until 9:07 a.m. Federal and state rules require immediate notification of spills.

The type of crack seen in the Coast Guard video is big enough to allow some oil to escape to potentially trigger the low pressure alarm, Kuprewicz said. But because the pipeline was operating under relatively low pressure, the control room operator may have simply dismissed the alarm because the pressure was not very high to begin, he said.

Ramanan Krishnamoorti, a petroleum engineering professor at the University of Houston, said the pipeline might have leaked for days before being discovered.

«If you have a massive crack or massive hole, you get a huge pressure drop and therefore you know you have a massive leak,» he said. «When you have a hairline crack like that, perhaps this could have been going on for two, three, four days.»

The fact that the San Pedro Bay line was still encased in concrete in the video is another indication that oil was likely leaking at a low rate. A major breach on a highly pressurized line would blow the concrete off, Kuprewicz said.

Because the line is encased in concrete — a means of keeping it weighted down on the sea floor — the Coast Guard video doesn’t reveal the condition of the half-inch-thick steel pipe underneath.

Once federal safety investigators cut out the damaged section of pipe and remove it, they will be able to conduct a closer examination, looking for signs of corrosion, metal fatigue or other anomalies that would have made it more susceptible to failure. That examination should also reveal if the crack grew larger over time, Kuprewicz said.