The culprit has now been identified as the SS Jacob Luckenbach, a 468-foot freight ship, that sank approximately 17 miles southwest of the Golden Gate Bridge as the result of a collision. The discovery is the culmination of an investigation by the US Coast Guard Marine Safety Office and the California Department of Fish and Game’s Office of Spill Prevention and Response (OSPR).
Initially, investigators had identified a number of oil tankers as possible causes of the spills, due to their routes and cargoes, and compared oil samples from them with those found on the oiled birds. However, none of the samples were found to be a match.
It was then found that 23 samples of oiled bird feathers and three samples of tar balls collected during the latest incident matched historical samples taken from similar mystery incidents in 1992-3, 1997-8 and February 2001. This led investigators to suspect either multiple releases from the same vessel or from a submerged vessel.
Satellite photographs, as well as observation from aircraft and patrol boats identified that there were oil sheens and tarballs southeast of the Farallon Islands, 52 km to the west of San Francisco in the Pacific Ocean. Databases revealed that there are a number of sunken ships in the area, including the chemical tanker Puerto Rican, which exploded and sank in 1984, the aircraft carrier USS Independence – intentionally sunk in the 1950s, and the Jacob Luckenbach.
“The investigation to identify the source of the mystery spill has been a scientific process of elimination,” said OSPR Deputy Administrator Scott Schaefer.
A submersible remotely operated vehicle was lowered down to the Luckenbach, which observed minor amounts of oil moving about in one of the ship’s cargo holds. Oil in and around the ship were found to match the spilt oil along the coast.
“This is very exciting. We’ve been trying to find the sources of mystery spills for years, so this discovery is truly gratifying,” said Bill Castle, Supervising Chemist at the state laboratory. “There’s a real sense of relief, because these spills create a big problem for us and for our wildlife.”
California’s governor, Gray Davis, was pleased that the source of the oil had finally been discovered. “I would like to thank the Department of Fish and Game’s Office of Spill Prevention and Response and the US Coast Guard for their tireless efforts in spearheading the search for the source of the oil spill that has depleted California’s offshore bird populations over the last ten years,” he said. “The comprehensive team approach with the State Lands Commission, the National Atmospheric and Oceanographic Administration, US Navy Salvage personnel, and the National Marine Sanctuaries, along with the response industry, brought together experts in oiled wildlife treatment and rehabilitation, satellite imagery, vessel operations, ocean currents, resource economics, wildlife behaviour, and oil fingerprint analysis.
The agencies are now working to prevent any further leaks from the vessel.