A day after a three-mile-wide oil sheen was spotted off the Santa Barbara Coast, authorities were trying to determine its source.
The slick was spotted about 1,000 feet offshore near Goleta Beach, an area known for natural oil seepage. But the size of the sheen made officials question whether it was naturally caused.
The sheen — no thicker than a coat of paint — did not force any beach closings, and the U.S. Coast Guard said the oily substance would dissipate on its own.
Federal officials said Wednesday’s sheen also could be the result of a spill in May, when a corroded pipe operated by Plains All American Pipeline leaked an estimated 101,000 gallons of crude along the Gaviota coast and forced a weeks-long closure of Refugio State Beach.
The director of the state’s Department of Fish and Wildlife, Charlton Bonham, said Wednesday the cleanup of the Refugio spill is ongoing, with about 14,000 gallons of oily water removed from the ocean.
Cleanup crews have responded to reports of tar balls as far away as Orange County, and one tar ball recovered in Manhattan Beach had the same oil “DNA” as the oil spilled at Refugio, he said.
Tar balls that appeared on Goleta Beach on Wednesday, while authorities were investigating the sheen, turned out to be from natural seepage, officials said.
Appearing in Sacramento before the state Ocean Protection Council, Bonham said the natural seepage in the area is challenging how his agency assesses the effectiveness of Refugio recovery efforts.
“What is clean?” he told the panel. “How clean is clean?’'
As federal and state investigators await the results of laboratory tests from Wednesday’s incident, Santa Barbara County’s director of public health, Dr. Takashi Wada, said there is no immediate risk to swimmers, and the county’s beaches and fishing piers remain open.
After swimming in the water off Goleta Beach with her friend, Anya Schmitz, 16, opined that the water was crystal clear — perfect for a summer dip.
“Conditions are great,” she said. “Seems like a lot of hype to me.”
The Coast Guard, meanwhile, said the sheen could have been an ordinary, natural seepage. At Coal Oil Point, a seep field in the Santa Barbara Channel, thousands of gallons of oil flow into the ocean each day, something residents have grown accustomed to.
“The earth burps all the time,” said Robert Hernandez, an electrician who fishes nearly every day off the Goleta pier. “You smell it, you get a little on you. No big deal.”
Initially described as measuring 60 feet wide, the sheen Wednesday evening had stretched 3.5 miles long and a half-mile wide, U.S. Coast Guard Lt. Ryan Schmid said. As tides moved, the oil split into sections and covered only about one-third of the total area, he said.
The patch was seen floating near an oil platform owned by Venoco Inc., but the company denied that its platform was involved. That platform, known as Holly, was shut down in May, a company official said. Its pipeline was flushed of any oil and refilled with seawater.
Yet environmental activist Rebecca Claassen, an organizer with Food and Water Watch, said it’s too early to minimize the sheen as a natural occurrence, adding that the oil platforms that dot the county’s coastline pose a daily risk.
“We can see a spill any day as long as there is drilling offshore,” she said.
Times staff writer Matt Hamilton contributed to this article.