Toxic Bog Lies Beneath Part of El Segundo

Officials from Chevron USA Inc. and the city of El Segundo Friday said they have detected low levels of potentially explosive, toxic fumes from a “gasoline mud pie” migrating underground through the city’s manufacturing district.

They said they are launching a comprehensive million-dollar study to determine how far the vapors have traveled and how to eliminate them.

Chevron, which operates an oil refining plant in the South Bay city, said the vapors were first detected last April when city workers were drilling holes for a storm drain project.

Chevron officials said that while they don’t know exactly how far the vapors have migrated, they estimate that the fumes are coming from a pool of liquid hydrocarbons about three or four city blocks wide and extending about a block outside of Chevron plant boundaries into the city itself.

Norman R. LeRoy, refinery manager of environmental affairs, said officials are “about 90% certain” that the vapors are traceable to operations at the refinery, which has had a history of problems with stagnant liquid hydrocarbon pools on its 1,000-acre site. Previously, the company had detected seven such pools, and has been pumping hydrocarbons from them for several years.

LeRoy, who said government and regulatory agencies were notified this week of the discovery, attributed the vapor migration to the sandy nature of the soil in the area, which allows the vapors to travel freely.

Describing the pool as a sort of “gasoline mud pie” sitting about 70 feet below the surface, Chevron toxicologist Rudy Von Burg said the vapors pose a potential short-term hazard because they become explosive at about 10,000 parts per million.

As part of the study, he said, officials will be monitoring more than a dozen businesses and residences in the area to determine whether the fumes could seep through sewer lines, utility cables or cracks in foundations.