Oil Sheen Shuts 8-Mile Stretch of O.C. Shore : Spill: The very light slick is near the Huntington Beach site where thousands of gallons leaked last year.

More than 8 miles of Orange County shoreline were closed to swimming Friday after a small amount of diesel fuel, probably dumped by a passing ship, caused paper-thin blotches of rainbow-colored sheen to spread across the ocean and wash ashore.

Haunted by memories of a large oil spill in nearly the same spot 18 months ago, Huntington Beach officials moved to clear the water from Golden West Street to the Santa Ana River because they feared the oily substance might be toxic and cause skin or intestinal ailments.

An estimated 20,000 beach-goers were on the 8.5 miles of shore when the orders to get out of the water came from lifeguards at 3:30 p.m. The affected area included Huntington State Beach--the second most popular state park in California.

The stretch of ocean, a favorite spot for surfers and bathers, was off-limits all Friday night and was expected to remain closed for part of today. But city officials said they hoped to reopen it by this afternoon. Beach-goers were allowed to stay on the sand, but no one was permitted near the water line.

Huntington Beach officials stressed that the spill was fairly small, but they made the difficult decision to ban bathing on a relatively crowded summer day because they wanted to take all possible precautions.

“It looks like somebody dropped diesel fuel or something out there,” said Ron Hagan, the city’s director of community services. “We’re going to have to look at the shipping-lane traffic to try to find the source.”

Coast Guard officials said the spill was roughly 20 to 40 gallons, or between a half-barrel and a barrel. Unlike crude oil, which is more viscous, a tiny quantity of diesel fuel can spread quickly over the water, creating a large, shiny film. Even a few gallons can form a sheen over miles of ocean.

The slick was spotted by a helicopter pilot at 11:15 a.m., and by 4 p.m., it was in small patches south of the Huntington Pier close to shore, spread over an area a mile and a half long and 200 yards wide, Coast Guard Lt. j.g. Mike King said.

Light, 10-knot winds and small swells were pushing the slick south. Most if it evaporated quickly, with only about 10% left by late Friday afternoon, said Chief Mark Lewack, a Coast Guard marine science technician.

Some oily film washed up onto shore at about 3:30 p.m., lightly staining sand in a 1 1/2-mile stretch from 5th Street, just north of the pier, to Beach Boulevard, about 1 1/4 miles south of the pier. No cleanup was planned because the sand was so lightly coated.

“It was so light that it could barely be seen,” said Martha Werth, spokeswoman for the Huntington Beach Fire Department. “It was hardly visible at all. Samples of it were taken and held up to the light and it was hard to distinguish any contamination.”

No injured wildlife or oiled birds were reported.

The sheen was creeping Friday afternoon toward sensitive Huntington Beach wetlands off the mouth of Talbert Channel, next to the Santa Ana River. City crews considered placing plastic booms at the river and channel mouths but decided against it when Coast Guard officials in helicopters at 4 p.m. said the sheen was breaking up and nearly gone.

Nonetheless, environmentalists spent some anxious hours.

“I’m very worried because it only takes a little bit of oil to cause damage to birds and other wildlife,” said Gordon Smith, chairman of the Huntington Beach Wetlands Conservancy, which manages the 25-acre marsh which was restored as a sanctuary two years ago.

Samples were taken for analysis, but results were not immediately available. Coast Guard officials believe it is diesel fuel because of its characteristic odor, Lewack said.

The oily material was probably bilge pumped out by a passing pleasure vessel or fishing boat, officials said, but the source will probably never be known because the boats are almost impossible to trace. Federal law prohibits such dumping, but it occurs frequently because the rules are difficult to enforce and witnesses are rare.

“Small nuisance spills are common . . . but we’re always worried about damage from any kind of spill, from whatever source,” said Brian Baird, the California Coastal Commission’s oil-spill expert. “You can see this is a pretty substantial impact--in the middle of summer, pulling people off the beaches.”

On Feb. 7, 1990, the American Trader tanker ran aground at a marine terminal off Huntington Beach, spilling 400,000 gallons of crude that fouled 15 miles of shoreline. That accident was nearly at the same spot where the sheen formed, and the same beaches were closed then.

“I suppose that with the city’s memory of what happened before there, they felt it was the best thing to do,” said Mary Gale, a spokeswoman for the state’s Office of Oil Spill Prevention and Response, an agency created in reaction to last year’s Huntington Beach spill. “Since this was the same stretch of beach that was affected before, it is probably being done as a precautionary measure.”

Huntington Beach emergency officials were momentarily swept with fear Friday because a large oil tanker was unloading crude at the terminal when the spill was spotted nearby. They quickly discerned, to their relief, that the spill was diesel, not crude oil, and that the tanker was not involved.

Lifeguards in boats and jeeps warned beachgoers through loudspeakers to stay out of the water. Some surfers and swimmers were unhappy, even though it was an overcast day with mediocre surf only about a foot high.

“It makes me feel real bummed out because I wanted to surf today,” said Dan Williams, 17, of Long Beach, who came to shore when lifeguards notified him of the closure. “They said something was in the water. They didn’t tell me what it was. Maybe some sort of chemical.”

State and county officials said they left it to the city to decide whether to ban swimming.

“The city is acting cautiously, and I support what they are doing,” said Robert E. Merryman, Orange County’s director of environmental health. “It’s not known what it is, or how much. If it’s diesel fuel, it’s not as bad as gasoline, but it could cause some minor irritations.”

Baird added that “when you’re dealing with a sheen that can come on shore, certainly you’ve got to take measures to protect the swimmers and surfers.”

Mayor Peter M. Green said the spill does not seem to be contiguous, but appeared in about 10 separate, oblong spots. That seems to indicate it came from a vessel spilling fuel while moving over the waves, he said.

Green said he believes it poses “no significant threat” to wildlife because the sheen is lighter than crude oil.

At about noon, the spill was reported to have spread over an area about 5 miles long, but most of it probably evaporated within a few hours, Lewack said.

“I have seen sheens out there from diesel fuel that are just a gallon or two and the whole world looks like it’s shining out there,” said Roy McClymonds, general manager of Clean Coastal Waters, the oil industry’s spill-cleanup crew stationed in Long Beach. “I suspect it’s some guy in his pleasure craft pumping his bilge out as he goes along. Unfortunately, they do that.”

Although McClymonds said he was alerted to the spill, his cleanup teams, which are on 24-hour spill duty, were not called out. Skimming boats were not used because the fuel was so thin that they would be unable to contain or pick anything up.

“It’s this little, skinny sheen. There’s not much that can be done to clean it up. There’s no substance there. It’s like trying to dam air,” Gale said.

King said the sheen was “measured in the hundredths of an inch.”

The spill apparently was first spotted by a helicopter pilot who had flown over the water to service an offshore oil platform. The Coast Guard was alerted by the pilot. Lifeguards also reported it, as well as workers on nearby oil platforms.

But Lewack said the spill apparently did not come from a platform. Officials say ships often discharge their bilge into the ocean when oil seeps into it because it is cheaper than getting it pumped out legally.

“There are a couple of small spills daily somewhere up and down the state,” Baird said. “Everything from overfilling a boat being fueled to many different sources.”

Times staff writers Kevin Johnson, David Reyes and Lily Eng contributed to this report, as did correspondents Jon Nalick and John Penner.

Swimming Banned After Spill 11:15 a.m.: Local officials receive the first reports of a mysterious spill. 1 p.m.: Early reports say a light oily sheen is about a mile long, from Huntington Pier to Beach Blvd. 3 p.m.: Mayor Peter Green, council members, other officials meet in emergency session. 3:30 p.m.: Splotches of oily material, probably diesel fuel, wash up on beach. City orders all bathers out of the water along 8.5-mile stretch. 4 p.m.: Coast Guard helicopter reports the sheen is in small patches spread over an area 1.5 miles long and 200 yards wide. About 90% has already dissipated.