A massive oil-related spill that occurred in central California over a 40-year period is spurring renewed scrutiny of the vast network of pipelines used to transport oil.
It highlights what many consider a ``hidden'' environmental problem in the United States: so-called chronic spills - leaks from storage tanks, pipes, refineries, and other facilities that happen over long periods of time.
The California case involves the leakage of as much as 8.5 million gallons of petroleum thinner at a Unocal Corporation oil field near Guadalupe, Calif., on the southern edge of San Luis Obispo County.
The spillage of diluent, a diesel-like fuel used to dilute heavy crude, adds up to the the state's largest spill and one of the largest in the country.
Last month, Unocal pleaded no contest to three criminal misdemeanor pollution charges in connection with the spill. It was ordered to pay $1.5 million in penalties. Now the company faces two civil suits, even as cleanup of the coastal site moves forward and others debate how to prevent similar mishaps in the future.
``We have a problem with aging infrastructure,'' says Mary Gale of the state Office of Oil Spill Prevention and Response, which has filed one of the civil actions against the company. ``Any pipe can break. The problem is when it breaks and isn't fixed.''
Each year, thousands of discharges occur at tank farms, production fields, airports, and other locations across the country. Many involve just a few harmless gallons. But others are far bigger.
``The chronic spills definitely represent a major hidden pollution hazard,'' says Richard Golob, publisher of Golob's Oil Pollution Bulletin, a Cambridge, Mass., newsletter.
About 146,000 barrels of crude were lost in pipeline accidents nationwide in 1991, according to the US Department of Transportation. Of roughly 3,000 spills reported to the California Office of Oil Spill Prevention and Response each year, pipeline leaks are the most common.
Yet that doesn't necessarily mean the problem is getting worse: A 1993 report by the California Fire Marshal, whose office oversees 7,800 miles of hazardous liquid pipelines in the state, found that ``leak incidents'' dropped 7 percent a year in the 1980s. The average cost of the damage, however, went up.
When Unocal first knew about the discharges is the source of considerable rancor. Company officials maintain that they were first alerted when a slick appeared in 1988. But they conducted tests that showed the pollution wasn't linked to their operations.
Two years later there was another slick. Even though company studies produced negative results again, the firm concluded it was responsible and reported the problem. It stopped using diluent and built an underground beach wall to try to stop further leaching from the on-shore field.
State investigators, however, have turned up evidence that indicates employees at the site were told not to call attention to repeated spills as early as 1978.
Company officials have since said they were stunned to learn of the magnitude of the leaks and disappointed by the failure of employees to notify authorities. They deny, however, there was a corporate coverup.
Disputed, too, is the spill's size. Unocal estimates it at between 4.6 million and 8.5 million gallons out of 1.2 billion gallons of diluent used. Some environmentalists believe the leaks could top the 10.1 million gallons that gushed from the Exxon Valdez.
Though no one knows how it has seeped into the sea, some 650,000 gallons have been siphoned from the beach since 1990. Unocal believes most of the thinner is sitting in plumes on top of the water table inland and is not seriously impacting surface habitat or marine life.
Environmentalists worry that enough has leached into the ocean to affect fish populations and marine mammals. On shore, there is concern about the impact on a wetland, groundwater, and on animal populations.
Unocal vows to spend whatever it takes to clean up the area - though there are, not surprisingly, disagreements on the methods it proposes and on its level of commitment.