Source: Federal Bureau of Investigation FBI Crime News (b)
In January 2021, the Los Angeles Port, one of the country’s largest and busiest shipping hubs, had effectively become a parking lot. COVID-19 had significantly slowed shipping rates globally, and dozens of 150,000-ton cargo ships were backed up and anchored in tight proximity to one another, creating a dangerous situation with little room for error. One or more of these ships was suspected to have damaged the pipeline. But the FBI would need to collect more data to narrow the list of which ships it could have potentially been.
In addition to assisting in the sample collection, USERT also worked to map the impact site. At 100 feet down with little natural light and murky ocean environments, the human eye could not effectively observe the surrounding area.
To address this, the FBI used sidescan sonar. Deployed from a remotely operated vehicle, the sonar would be pinged repeatedly. The intent was to divide the area into grids and use multiple sidescan sonar launches to fill in the grids. Dozens of missions over time would yield data for the entire area.
There are several things one can infer from sonar data, including the time it takes the sound to return gives depth. And the strength of the return can tell you what kind of material the sound is reflecting off of. A weak signal indicates muddy, sedimentary ocean floor. Stronger signals can indicate rocky bottom or foreign objects such as metal and concrete.
Summers turned the raw sonar data into a picture of the ocean floor around the break site that showed a few key details. First, the pipeline indeed was out of alignment from where it should have been, another indication it had been dragged. Second, in the soft ocean floor were furrows—scars left by an anchor that had dragged across the ocean floor and ultimately had snagged on the San Pedro pipeline.