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HUNTINGTON BEACH, Calif. (AP) – A Southern California submarine pipeline was likely struck by an anchor several months to a year before a leak spilled tens of thousands of gallons of crude, said Friday. US Coast Guard.
A large ship of some sort may have struck the massive pipeline, shattering the concrete casing but not necessarily causing the thin crack from which the oil spat out last weekend, said Captain Jason Neubauer, Head of the Coast Guard’s Bureau of Investigation and Analysis.
The longer timeline was in part based on the marine growth that was spotted on the pipe during an underwater survey.
The pipe, which was found to be intact last October, may also have been struck several other times by anchors from other vessels during the period, he added.
However, no vessel has been identified.
“We will be looking at every vessel movement on this pipeline and every encroachment near the anchor throughout the year,” said the captain.
The pipeline was dragged along the seabed up to 105 feet (32 meters), Neubauer said.
This indicates that a large ship was involved, he said. Freighters with anchors weighing several tons regularly cross the area from the ports of Los Angeles and Long Beach.
The leak contaminated beaches and killed seabirds.
At least 17 accidents on pipelines carrying crude oil or other hazardous liquids have been linked to suspected anchors or anchors since 1986, according to an Associated Press review of more than 10,000 reports submitted to federal regulators.
According to federal records, in some cases an anchor strike is never conclusively proven, such as the 2012 leak of an ExxonMobil pipeline in the shallow bay of Barataria in Louisiana, where a direct strike by a barge or another boat was also considered.
In others, the evidence of an anchor was evident. During Hurricane Andrew of 1992, a 30,000-pound anchor was dragged by a drifting drilling rig on a Texaco pipeline in the Gulf of Mexico, causing a breach that opened when the line then broke. been restarted.
In 2003, a 7,000 pound anchor was found about 10 feet from a small spill on a Shell oil pipeline in the Gulf.
A Coast Guard video released Thursday appears to show a trench in the sandy bottom leading to a bend in the submerged line, but experts have offered varying opinions on the significance of the short grainy shots. A previous video presented a thin break 13 inches (33 centimeters) long in the line.
Robert Bea, an engineering professor at the University of California at Berkeley and a former Shell Oil engineer, said the second video appears to show a groove in the seabed created by a drag anchor leading to the damaged pipeline.
Investigators should, however, take into account other forces that could have moved and damaged the pipe, including water currents that move through the seabed.
It will take time.
“The results of the analyzes must be validated and corroborated. This process may raise even more questions, ”said Bea. “The shape of the crack indicates that it was caused by internal pressures in the pipeline. But, if that’s true, why didn’t the pipeline leak ”sooner?
Frank G. Adams, president of Houston-based Interface Consulting International, said in an email that the slight bend in the line shown in a video “doesn’t necessarily look like anchor damage.”
When a pipeline is struck by an anchor or other heavy object, “it usually results in physical damage that can lead to fracture,” he said.
Reports of a possible spill off Huntington Beach were first published on Friday evening, but the leak was not discovered until Saturday morning. Although the extent of the spill is not known, the Coast Guard has slightly revised the parameters of the estimates to at least about 25,000 gallons (95,000 liters) and not more than 132,000 gallons (500,000 liters).
The Coast Guard said about 5,500 gallons (20,819 liters) of crude was recovered from the ocean. The oil spread southeast along the coast with reports of small amounts landing in San Diego County, about 50 miles (80.47 kilometers) from the original site.
Local health officials said on Friday that air samples from areas where oil could spill were in the background levels – in other words, similar to the air quality over the course of a typical day – and below California health standards for the pollutants measured.
So far, the impact on the wildfires has been minimal – 10 birds dead and 25 others recovered alive and treated – but conservationists warn that the long-term impacts could be much greater. As the cleanup continued on the shore, some beaches in Laguna Beach reopened on Friday, although the public still couldn’t get in the water.
Investigators are trying to determine what happened in the first crucial hours after the first reports of a possible oil spill.
The narrow gash seen in a video could explain why signs of an oil slick were seen on Friday evening, but the spill escaped detection by the pipeline operator for more than 12 hours.
“My experience suggests this would be a damn difficult leak to determine remotely quickly,” said Richard Kuprewicz, a private pipeline accident investigator and consultant. “An opening of this type, on a 27-kilometer-long submarine pipe, is very difficult to spot by indications from a distance. These crack-like releases are weaker and can last for some time. “
When pipes fail catastrophically, the breach is usually much larger, what is known in the industry as a “fish mouth” rupture, because it is gaping like a fish’s mouth. -he declares.
Amplify Energy, a Houston-based company that owns and operates three offshore oil rigs and the pipeline south of Los Angeles, said it did not know there had been a spill until its employees detect an oil burst on the water at 8:09 a.m. on Saturday. a m
The leak occurred about 8 kilometers offshore at a depth of about 30 meters, investigators said. A 4,000-foot (1,219-meter) section of the pipeline was dislodged 105 feet (32 meters), bent like a bowstring, Amplify CEO Martyn Willsher said.
Jonathan Stewart, professor of civil and environmental engineering at the University of California at Los Angeles, said moving a large section of pipe this far would have caused “bending deformations” – a strain on the side that was stretched in half. circle, with one squeeze on the other, as it was bent inward, says Stewart.
It’s possible that such pressure alone could lead to a rupture, although Stewart said there was too little information to draw a conclusion about the cause. It is possible that a sharp anchor section could pierce the pipeline, but “you could still suffer damage just from the bending.”
“Because it pulls on the pipe, you create these bending stresses in the pipe, which could eventually become large enough to break it,” he said.
Questions also remain about when the oil company knew it had a problem and a potential delay in reporting the spill.
A foreign vessel anchored in the waters off Huntington Beach reported to the Coast Guard that it saw a burst of more than 2 miles just after 6 p.m. on October 1 and that evening, an Agency satellite image Space also indicated a probable oil slick, which was reported to the Coast Guard at 2:06 a.m. Saturday, after being examined by an analyst with the National Oceanic and Atmospheric Administration.
Federal pipeline safety regulators set the time of the incident at 2:30 a.m. on Saturday, but say the company did not shut down the pipeline until 6:01 a.m. – more than three hours after the outbreak of ‘low pressure alarm indicating a possible problem – and did not report the leak to the Coast Guard until 9:07 am Federal and state rules require immediate notification of spills.
Amplify said the line had already been shut down at 6 a.m., then restarted for five minutes for a “meter reading” and closed again. A meter reading shows the amount of oil entering and leaving the line. The company could have used this information to confirm whether the pressure change alarm went off because the pipe was leaking, said Kuprewicz and Ramanan Krishnamoorti, professor of petroleum engineering at the University of Houston.
The company said a boat discovered oil on the water at 8:09 a.m.
(Copyright (c) 2021 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)
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