TORRANCE — State officials say they no longer believe there is a danger of fire and explosion from a pool of leaked gasoline and oil under the Mobil Oil Corp. refinery.
In addition, test readings indicate that leaks from the Mobil refinery, the Shell and Arco refineries in Carson, the Unocal refinery in Wilmington and the Western Fuel Oil tank farm in San Pedro have not contaminated underground drinking water, according to state officials and water industry spokesmen.
Nevertheless, tests are continuing to determine the likelihood of future well-water contamination.
"It is OK for now," Gary Yamamoto, a district sanitary engineer with the state Department of Health Services, said this week. "But if we don't do something about it, one doesn't know what might happen in the future. . . . If there are pools of hydrocarbons under the refineries, they may not have gotten deep enough yet" to contaminate well water.
Tests Ordered in '85
Officials ordered refineries to test for underground pools of oil and gas in February, 1985, after Chevron USA reported finding a pool of gasoline beneath its El Segundo refinery which had migrated into nearby residential areas.
Because ground water is close to the surface near the El Segundo refinery, the fuel floating on top is also close to the surface. A ground ventilating system was installed after high concentrations of fuel vapors were reported at nearby residences.
Fearing similar conditions elsewhere, state officials ordered all refineries in the county to dig wells to test for underground gas and oil.
Mobil reported finding a layer of gas and oil--25 feet at its thickest--about 75 feet below the surface of its Torrance refinery, close to residential areas. The exact size of the hydrocarbon deposit has not been determined. Pools reported by the other South Bay refineries were contained on refinery property and did not menace residential neighborhoods, state officials found.
Worried that Mobil's underground oil and gas had migrated under residential areas, state officials ordered special tests in the neighborhoods near the Mobil refinery--checking sewer and underground electrical and telephone conduits where vapors might be trapped.
Before conducting the tests, officials said that the depth of the deposits under the Mobil plant probably would dilute the fumes. Some of the hydrocarbons near the Chevron plant were just 10 feet beneath the surface.
Indeed, "we found nothing," said Nestor Acedera, chief for assessment and mitigation with the Southern California Division of Toxic Substances Control Division of the state Department of Health Services.
Concern then shifted to ground water contamination.
"So far we have been extremely lucky," said John Joham, executive secretary of the West Basin Water Assn., which represents water companies supplying 800,000 people in the South Bay.
Protected by Clay
Vast underground sheets of clay apparently keep contaminated ground water from reaching the depths from which drinking water is pumped, according to Joham and Yamamoto. The hydrocarbons leaking from the Mobil refinery float atop a layer of ground water. Torrance has two wells near the plant, which pump drinking water from 200 feet down.
In addition, underground water flow from west to east carries tainted water away from the wells, said Torrance water system Superintendent Robert O'Cain. One of the wells is about a mile west of the Mobil refinery. The other is about a mile south.
Acedera said research is being conducted to map the clay deposits to find out if water from one body of water will migrate into another, possibly spreading contamination.
Joham said, "I think we have been fortunate mainly because of where we are living. The area provides a natural protection."
Some Wells Closed
In other areas, including Southgate, Norwalk and Hollydale, water officials have had to shut down wells because of refinery contaminants discovered in drinking water, Joham said.
Despite the lack of contamination in the South Bay, state officials want the underground oil and gasoline removed. "Shallow (contaminated) ground water may spread beyond an area where they can control it," Yamamoto said.
A Mobil spokesman said refinery officials are researching ways of extracting the underground gasoline and oil.
"We are developing techniques. It is not an easy matter to pump the oil out," said Thomas Gregory, manager of environmental and community relations for the Mobil refinery.
Chemical analysis showed that the hydrocarbons are as much as 20 years old. Refinery officials say routine maintenance programs have probably repaired most or all of the leaks.