Oil Spill Contamination Feared : Pollution: Officials are monitoring wells beneath the Santa Clara River and state fish and game crews are attempting to rescue wildlife.

As crews cleaned up oil spilled from a ruptured pipeline, officials Saturday expressed increased concern over environmental damage to the Santa Clara River and continued to monitor Ventura County water wells for contamination.

Under overcast, drizzly skies, teams of biologists worked to assess the damage to the river, contaminated by more than 63,000 gallons of crude oil that gushed from a ruptured Mobil Oil pipeline Friday. At some points along the river, thick oil floated on the surface and the black crude coated plants along the banks.

Officials from the state Department of Fish and Game said the oil spill could harm two endangered species. The waterway is one of the last habitats for the armored stickleback fish and is an important nesting ground for the least Bell’s vireo.

By Saturday afternoon workers had recovered and washed 18 oil-drenched birds. None of the birds, however, was a least Bell’s vireo.

“We are very concerned about the damage,” Capt. Roger Reese of the fish and game department said.

Mobil Oil Corp. officials said the spill was caused by an 18-inch-long crack in a 21-year-old section of the pipeline east of the Golden State Freeway near Magic Mountain.

The pipe section was replaced and the line was back in operation by midnight Friday, Mobil spokesman Tim Salles said. Salles said about 100 cleanup workers have been on-site since Friday. The effort will take several weeks.

Mobil Oil Corp. officials said the oil was contained about 12 miles downstream from the rupture.

Ventura County officials with the United Water Conservation District said they are monitoring wells beneath the river. The wells are several miles downstream from the point of containment.

Water officials will not know until mid-week whether dangerous levels of carcinogens have reached the water supply, which serves 300,000 Ventura County residents. If high levels of the carcinogen benzene or other harmful chemicals are detected in the underground basins, United will pump the water out and dispose of it.

On Saturday, crews tended booms and filters that had been set up to trap and absorb the oil moving on the surface.

Giant vacuum trucks were deployed to suck up the oil sludge. Workers in yellow slickers stood nearly knee-deep in the water soaking up oil and residue with giant white “diapers,” super-absorbent sheets of cotton and polyester. Crews also began scooping up oil-contaminated dirt from the stream bed and hand-washing plants and trees.

The work will be “slow and very labor-intensive,” Salles said.

Salles said it was too soon to estimate the cost of the effort or the amount of contaminated dirt.

Meanwhile, fish and game wardens and environmentalists from the Berkeley-based International Bird Rescue Service combed the stream bed Saturday for oil-soaked birds and fish.

By mid-afternoon Saturday, more than 18 birds--including several varieties of ducks and a great blue heron--had been cleaned at an emergency cleaning station. They were taken to a wildlife refuge at Terminal Island, where they will remain several days for observation, John Hernandez, fish and game warden, said.

As he spoke, a snowy white egret--its legs a dark, oil-stained black--soared overhead.

“See that? His legs, they should be white,” he said.

Jay Holcomb, a bird rescuer, carried oil-soaked mallards and widgeons to the cleaning station. He found six dead birds Saturday, including one heron. Workers also found about four dead fish--none of them sticklebacks.

Reese predicted that the count of dead and sickened birds will probably increase in the next few days as rescuers search for fowl among the brush and vegetation along the river, which is partially fed by stream waste-treatment water.

Birds and mammals can become sickened by drinking contaminated water, biologists said. Also, when bird feathers become drenched with oil, the animals can suffer from hypothermia and become dehydrated, Reese said.

Eventually, the birds “will get cold, lose energy and get tired,” Reese said. “They’ll get sick and I am sure some of them are going to die.”