Oil From Offshore Pipe Break Creates 2-Mile-Long Slick : Environment: The spill off the coast of Oxnard is estimated between 10 and 50 barrels. Cleanup is hampered by choppy seas.

A Unocal oil platform four miles off the coast of Oxnard spilled between 420 and 2,100 gallons of crude oil Friday when a work boat dragging the bottom to retrieve an anchor accidently ripped open a pipeline that carries oil to shore, federal authorities reported.

Seven cleanup boats had moved into the area by Friday evening to try to contain the spill that had dispersed into a slick two miles long and 1,000 feet wide. Automatic sensors on platform Gina quickly shut off the 10-inch diameter pipeline, preventing the escape of additional oil, said Unocal spokesman Barry Lane.

The slick was headed toward Ormond Beach in south Oxnard, Lane said. Although specialists did not know if oil would hit land, Unocal dispatched cleanup crews to the beach. The company also took the precaution of directing crews to unfurl a floating plastic containment boom at the mouth of Mugu Lagoon, an ecologically sensitive estuary.

“No one knows how much oil actually spilled. The best range we’ve got is 10 to 50 barrels. It’s not a very large spill,” Lane said. A barrel is 42 gallons.

Before dark Friday, crews on cleanup vessels placed a floating boom around the leading edge of the slick, which had dispersed mostly to a thin sheen, Coast Guard Lt. Steve Danscuk said.

But the wind and choppy waters grew through the afternoon, hampering cleanup efforts, authorities said. By early evening, crews were working in 6-to-8-foot swells and in winds as high as 20 m.p.h. “It’s a little tough to contain oil in conditions like that,” Danscuk said.

Late in the day, the Coast Guard recommended that Unocal ask the state’s permission to spray a chemical dispersant on the slick, said Dena Winham, a spokeswoman for the U.S. Minerals Management Service.

Oil company crews must receive permission from state authorities to use dispersants because the chemicals are toxic. Winham said the Coast Guard usually does not call for dispersants unless they fear a slick will reach shore.

The Unocal pipeline was ruptured about 2 p.m., when an oil crew work boat was grappling for an anchor lost from a buoy near the platform, Lane said. The boats tie to the buoy when bringing supplies and crew members from the mainland to platform Gina, about four miles southwest of Oxnard.

“Apparently, they snagged the pipeline about 200 yards north of the platform and pulled on it until it broke,” Lane said. “The break occurred right at the bottom of the platform.”

Cleanup experts estimated that between 10 and 50 barrels of oil escaped from the pipeline before safety valves isolated the rupture, Winham said.

The small pipeline carries about 1,250 barrels of oil a day about six miles to an oil-and-water separation station at Mandalay State Beach, Lane said. From there, the oil is carried by pipeline to refineries, he said.

Oil crews were expected to work through the night, he said. The crews included those from Clean Seas, a oil cleanup cooperative based in Carpinteria.

Unocal is also the owner of the offshore drilling platform that created the worst accident in California history.

In 1969, a blowout at Unocal’s Platform A off Santa Barbara unleashed 77,000 barrels of crude from the ocean floor. The slick spread to beaches in Ventura and Santa Barbara counties and to the Channel Islands. The incident touched off a nationwide environmental movement.