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Though anchor strikes are rare, severe weather is associated with their occurrence. Most offshore oil drilling infrastructure is designed to withstand so-called 100-year storms, giant rainfall events estimated to have a 1% chance of occurring at that location each year. But some climate experts warn that those predictions may not account for climate change, which is bringing more intense weather more often. Hurricanes in particular have wreaked havoc on underwater infrastructure, stirring up winds forceful enough to blow even large container ships off course, break the moorings of offshore platforms and leave both dragging heavy anchors across the seafloor. Off the Southern California coast, government regulators signed off decades ago on a plan to bury a section of the pipeline, which runs more than 15 miles between a processing platform called Elly and the shore. The buried section would run from the shore to the Long Beach breakwater. From there, the rest of the line lies on top of the seabed. Initially, the buried part of the line was to be 4 feet under the seabed. But after concerns expressed by the U.S. Coast Guard that the depth might not be enough to prevent damage caused by maritime activities, company officials agreed to bury the line at least 10 feet below the seafloor. The analysis — included in an environmental impact report prepared in 1978 by the U.S. Geological Survey, the State Lands Commission and the Port of Long Beach — acknowledged that there was still a chance of an anchor strike along the unburied part of the line, which runs nearly 11 miles along the ocean floor. But it downplayed the potential spill. “There remains the possibility that the pipeline could be ruptured or pierced by an accident, such as an emergency or accidental anchoring,” the report said. “The amount of oil spilled from the pipeline in the event of such an accident, because of the nature of the oil and the pipeline configuration, would probably be small.” Part of the analysis relied on an overly rosy prediction that a pipeline leak detection system would work effectively enough to prevent larger spills, experts said. Robert Bea, a UC Berkeley professor emeritus of engineering and project management and systems, said that the 50-barrel spill estimate was “sketchy superficial” and that there didn’t appear to be data to support such a scenario. “It sounds like what I call guesstimating,” said Bea, who helped design the oil processing platform Elly. Now, investigators have the task of trying to identify when the anchor strike occurred and which ship was involved. In some prior rupture cases, anchor strikes were strongly suspected but investigators were unable to confirm the cause.
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