The test results ruled out the possibility that the oil came from the Nov. 7 Cosco Busan oil spill in San Francisco Bay. That event polluted Bay Area waters - including the San Mateo County coast - with 58,000 gallons of oil.
Due to the quantity of last week's tar balls, officials had been laboring under the working theory that the latest round of oily debris originated from the commercial freighter that scraped against a Bay Bridge footing late last year.
 Workers toil to remove tar that washed ashore on Half Moon Bay-area beaches in the wake of powerful winter storms. Officials say the oily residue that appeared last week was a naturally occurring phenomenon and had nothing to do with the November Cosco Busan accident. |
"Just the amount is far greater than we would typically see on (a regular) day," said Dean Peterson, San Mateo County director of environmental health, before test results came back the morning of Jan. 30. Peterson added that "maybe five tar balls" wash up on Fitzgerald Marine Reserve once or twice per year.
"As the sea floor moves, oil is sometimes released and stormy weather often washes the substance ashore," according to a U.S. Coast Guard statement released Friday. The California Department of Fish and Game's petroleum laboratory tests in Rancho Cordova confirmed that the tar balls "were of a naturally occurring release from the ocean floor," the statement said.
Workers also found a number of dead birds during their cleanup efforts, but officials said that the precise cause of the birds' death is unconfirmed, and that the impact to wildlife was minimal.
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